TABLE OF CONTENTS

INTRODUCTION INJECTION MOLDING

5 Product Description 19 Ty pical Processing Temperatures

5 Product by Grade Type 19 Barrel Heating Zones
5 Product by Market 19 Nozzle
6 Nomenclature 20 Melt Temperature
6 Grade Designation 21 Machine Conditions
6 Color Designation 21 Injection Pressure
7 Packaging and Labeling 21 Hold Pressure
22 Injection Speed
22 Injection Cushion
MACHINE SELECTION 23 Back Pressure
8 Machine Type and Design 23 Screw Speed
8 Screws: Material, Configuration, 24 Clamp Tonnage
and Wear
24 Mold Temperature
10 Non-Return Valves
25 Mold Temperature Control
11 Nozzles: Types and Tips
26 Residence Time
11 Nozzle Materials
27 Cycle Time
11 Nozzle Size
27 Mold Release Agents
11 Nozzle Temperature Control
27 Part Shrinkage
12 Process Controls
28 Part Ejection
12 Temperature
28 Color Concentrates
13 Time and Pressure
28 Using Regrind
13 Shot Size and Machine Capacity
29 Post-Mold Conditioning
13 Machine Ventilation
30 Unreinforced
31 Reinforced
32 Machine Preparation
DRYING
32 Purging and Cleaning
15 Material Handling
33 Start-Up Procedure
15 Drying Equipment
33 Shutdown Procedure
16 Drying Conditions
33 Short-Term Shutdown
33 Long-Term Shutdown

1 of 65
TABLE OF CONTENTS, continued

TOOLING
47 Short Shots /Cold Flow
35 Mold Design 48 Sinks /Voids
35 Material Selection 49 Sticking: Cavity/Sprue
35 Surface Finish 50 Poor Surface Finish/ Lack of Gloss
35 Venting 51 Warpage/Part Distortion
36 Part Draft 52 Weld Lines
36 Texturing
36 Weld Lines
36 Undercuts SAFETY CONSIDERATIONS
36 Tolerances 53 General
36 Mold Types 53 Health and Safety Information
36 2- or 3-Plate Molds
37 Single- and Multi-Cavity Molds
37 Sprue Considerations GENERAL INFORMATION
37 Sprue Bushings 54 Developmental Product Information
37 Sprue Pullers 54 Regulatory Compliance
38 Runners and Runner Systems 54 Technical Support
38 Hot Runner Molds
38 Gating
39 Edge Gates APPENDIX A
39 Pinpoint Gates 55 List of Tables
39 Sprue Gates
40 Tunnel Gates
40 Ring (or Diaphragm) Gates APPENDIX B
40 Insert Molding 56 List of Figures
40 Molded-In Stress

INDEX
TROUBLESHOOTING GUIDE
58 Index
41 Burn Marks
42 Dimension Control
43 Discoloration
44 Flash
45 Nozzle Drool
46 Nozzle Freeze-Off

3 of 65
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 OF 
NOMENCLATURE The grade designation for Durethan Table 1 lists the grade composition and
Grade Designation resin consists of three parts: designations for Durethan polyamide 6
resins. Table 2 lists the performance
There are two groups of Durethan 1. Prefix A series of letters additives and designations.
resins: Durethan “A” resins, which are describing the grade
polyamide (nylon) type 66 engineering composition.
polymers; and Durethan “B” resins, Color Designation
which are polyamide type 6 resins. 2. Grade Number A number indicating
LANXESS Corporation offers viscosity for un- Opaque colors, as well as natural tints,
primarily Durethan B resins in filled grades and are available in pellet form. The color
the United States plus speciality grades the amount of filler coding system for Durethan polyamide
of Durethan “C” copolymer and in reinforced grades. is listed in Table 3.
Durethan “T” transparent resin.
3. Suffix A letter indicating
the type of perform-
ance additive in
the grade.

Performance Additives and Designations for

Table 2 Durethan Resins Table 3 Color Coding System for Durethan Polyamide Resin

Performance Color Code

Additive Designation
Natural 1000 – 1499
Heat Stabilized H
Blacks 1500 – 1999
Internal Mold Release S
Grays 2000 – 2999
Nucleating Agent K
Whites 3000 – 3999
Mixed Filler X
Browns 4000 – 4999
Antioxidant W
Yellows 5000 – 5999
Impact Modified (Low) Z
Oranges 6000 – 6999
Reds 7000 – 7999
Blues 8000 – 8999
Greens 9000 – 9999

6 of 65
 INTRODUCTION, continued

PACKAGING AND LABELING The bags and cartons are sealed to help carton of Durethan resin sealed until it
prevent contamination from dust or dirt. is to be used and avoid storing it in
All injection molding grades of Be careful when opening and resealing areas that are subject to high humidity.
Durethan resin are supplied as dried them that dust or dirt does not get in (See also “Drying,” page 15, for more
pellets in vacuum-sealed, moisture- among the clean resin. Any particulate information.)
tight, multi-walled 55-lb (25-kg) bags. contamination in the feedstock will
A pallet of 30 bags weighs 1,650 lb show up in the finished molding. If properly sealed in their bags, most
(750 kg). The pallets are shrink- grades of Durethan resin can be stored
wrapped for shipping. Take care not Durethan resin is hygroscopic and will for at least one year if not exposed
to slit the bags when removing the begin absorbing moisture as soon as it directly to the weather. If the resin is to
shrink-wrapping. is exposed to the air. Resin which has be stored outdoors, you must protect
become moisture-contaminated can the bags from sunlight and rain, which
Some grades are available in 1,102-lb cause injection molding problems. can deteriorate the packaging.
(500-kg) or 2,204-lb (1000-kg) boxes. Resin exposed to moisture for more
Boxed resin is also dried and sealed in than a few hours and processed without An example of a label for Durethan
special liners. having been properly dried will suffer a resin is shown in Figure 2.
permanent reduction in physical prop-
erties. Therefore, keep each bag or

Durethan Polyamide
Figure 1 Figure 2
Resin Pellets Label Information for Durethan Polyamide Resin

IN CASE OF EMERGENCY CALL: CHEMTREC 800-424-9300

/$1;(66&RUSRUDWLRQ
Bayer Coroporation
5,'&3DUN:HVW'ULYH
100 Bayer Road
Pittsburgh PA
3LWWVEXUJK3$
15205-9741

7 of 65
 MACHINE SELECTION

MACHINE TYPE AND DESIGN ● Nozzle type. metering and feed zone depths are
shown in Figure 5.
Reciprocating screw machines are ● Size and location of mold gates.
preferred for injection molding ● Screws with a length-to-diameter
Durethan resins. Of the conventional A typical reciprocating-screw injection ratio (L/D) in the range of 18:1–
injection molding machines available, molding machine is shown in Figure 3. 22:1 are recommended. An L/D ratio
they provide the most uniform plasti- of 20:1 is preferred. If a shorter
cating of molten material. screw is used, reduce the screw pitch
SCREWS: MATERIAL, to obtain 20 flights, as shown in
The design of reciprocating screw ma- CONFIGURATION AND WEAR Figure 6.
chines has many variables, including:
The following are important considera- ● Screws with an L/D ratio greater
● Screw length, diameter, and tions in choosing a screw for injection than 22:1 can cause material degrad-
configuration. molding Durethan polyamide resin: ation. Once again, if a shorter screw
is used, reduce the pitch to obtain
● Number and wattage of barrel heaters. ● A three-zone general-purpose screw 20 flights.
of traditional geometry is recom-
mended (see Figure 4). The preferred

Figure 3 Figure 4
Typical Injection Molding Machine Typical Injection Molding Screw

8 of 65
 MACHINE SELECTION, continued

● Best results are achieved when the ● Use screws made of surface-hardened Durethan resins, which are crystalline
flight-to-depth ratio of the feed sec- steel for injection molding glass- thermoplastics, require high plasticizing
tion to the metering section is fiber-reinforced or mineral-filled efficiency because of their high specific
between 2.0:1 and 2.5:1. Durethan resin. The glass fibers can heat. Short screws and high throughput
chip and abrade the chrome plating, rates will accomplish this. Special
● The screw pitch should equal the contaminating the melt. screws with reduced flight depths and
screw diameter for diameters less shorter pitches may be required in some
than 3.2 in. (80 mm). The screw ● An abrasion-resistant, bimetallic cases.
pitch should be about 90% of the barrel liner, such as Xaloy,* is
diameter for screw diameters greater preferred. Avoid using worn barrels, Avoid using increasing-core-diameter
than 3.2 in. (80 mm). since they can develop a layer of (progressive core) and short-transition-
degraded resin that can break loose zone types of screws for processing
● Screws should be chrome-plated and and contaminate the melt. Durethan resins. These types of screws
highly polished. The flight lands may not produce a homogeneous melt,
should not be plated, however, thereby causing inconsistent results.
because the plating may chip off
and contaminate the resin melt. *Xaloy is the registered trademark of Xaloy, Inc.

Preferred
Screw Flight
Figure 5 Screw Profile Depths Figure 6

.500

h
pt
.400

De
ne
Zo

.300
ed
Fe
DEPTH ZONE (in.)

.200
epth
Zone D
g
.100 erin
Met

0 1 2 3 4 5

SCREW DIAMETER (in.)

9 of 65
NON-RETURN VALVES Good flow characteristics are an impor- With small-diameter screws, keep the
tant requirement of the non-return valve shear gap length under 0.080 in.
A free-flowing, sliding check-ring non- because Durethan polyamide, like other (2 mm). Even with large-diameter
return valve is recommended for injec- thermoplastics, will degrade when sub- screws, keep the length under 0.160 in.
tion molding Durethan resins (see jected to excessive shear at flow (4 mm).
Figure 7). It prevents the molten poly- restrictions.
mer in the holding space in front of the The valve and check ring are subject to
screw from flowing back into the screw For strength, the check ring of small- severe wear, especially when molding
during the injection cycle. Ball-check diameter screws often has a larger glass-fiber-reinforced plastic. Make
valves are not recommended. external diameter than the screw frequent visual inspections of the non-
core. The shear gap that is formed return valve to see that it is functioning
Good flow characteristics, as shown between the ring and screw can cause properly.
in Figure 8, are essential. A fully degradation and discoloration when
channeled tip will minimize flow shear-sensitive grades and pigments are
restrictions. processed. Therefore, this seal flange
should be only as large as necessary for
the strength of the check ring.

Free-Flowing Sliding Check-Ring-Style

Figure 7 Non-Return Valve
Flow Characteristics of the
Figure 8 Non-Returning Ring Valve

10 of 65
 MACHINE SELECTION, continued

NOZZLES: TYPES AND TIPS Nozzle Materials Proper mating and firm seating of the
nozzle and sprue bushing are essential.
Nozzles are available with and without Standard steel nozzles are acceptable. The nozzle discharge opening must not
removable tips (see Figure 9). The melt However, type 420 stainless steel offers exceed the diameter of the sprue bush-
viscosity of Durethan resin is low better protection against black specks in ing inlet, otherwise it will form an
enough that the melt can leak or drool long production runs. undercut that could stick to the sprue.
from the nozzle between injection To promote material flow, the nozzle
cycles and blemish the molded part. opening should be at least 80% of the
Adjustments to the nozzle temperature Nozzle Size diameter of the spure bushing inlet.
and suck-back settings usually correct
drooling problems. Occasionally, a The nozzle should be as short as possi-
shut-off nozzle is required to prevent ble with its internal diameter deter- Nozzle Temperature Control
drool. Two common types of shut-off mined by its length and required
nozzles are the sliding shut-off nozzle throughput. Nozzles up to 6 in. The nozzle must have an independent
and the needle shut-off nozzle (see (150 mm) long require an internal heater and controller system to main-
Figures 10 and 11). diameter of 0.375 in. (9 mm). The tain the proper nozzle temperature
major inside diameter at the threaded because heat drained from the nozzle
end should be exactly equal to the by the mold can cause the melt to cool
diameter of the end cap. enough to solidify. Permitting the

Removable and Non-

Figure 9 Removable Nozzle Tips Figure 10 Sliding Shut-Off Nozzle

11 of 65
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 OF 
 MACHINE SELECTION, continued

and movement of the screw. Nor can a The temperature measured by the Shot Size and Machine Capacity
sensor easily be sealed against leakage sensor is seldom exactly equal to the
at the high injection pressures. temperature of the plastic melt. There- Utilization of 25% – 65% of the barrel
fore, adjust cylinder and nozzle tem- capacity is preferred. Excessive resi-
The solution, then, has been to locate perature set-points to get an actual dence time at elevated temperatures can
temperature sensors in wells drilled into measured melt temperature that is with- cause Durethan resins to degrade. It is
the cylinder walls and regulate melt in the recommended range for the grade recommended that the material remain
temperature by measuring and control- of Durethan resin being processed. in the barrel at processing temperatures
ling the cylinder wall temperature. for no longer than 10 minutes, on
average.
However, the depth of the well affects Time and Pressure
the temperature measured by the sensor,
since a temperature gradient exists in Uniform molding cycles are essential to Machine Ventilation
the cylinder wall. To minimize this maintaining optimum processing con-
effect, the thickness of the steel at the ditions and producing the highest- A ventilating hood should be located
bottom of the well is usually equal to quality parts. State-of-the-art closed- at the front or nozzle end of the mold-
its diameter. loop control systems can ensure both ing machine to remove any fumes
the precise injection stroke and switch- generated during injection molding
In order to further minimize error, peri- over point that are critical for molding or purging.
odically check to make sure that the quality parts. They can adjust hold
sensors are clean and fit firmly in the pressure in increments to minimize
wells. Impurities, such as charred pel- sinks and voids. In addition, they can
lets, or a cushion of air between the maintain melt pressure in the mold
cylinder wall and the sensor have led cavity uniformly from shot to shot
to readings that are inaccurate by as despite variations in the operating
much as ±54°F (±30°C). conditions of the machine.

Some advanced controls adjust the

holding pressure and cooling time to
ensure that each part is ejected from
the mold at the same temperature and
weight. This improves part-to-part
weight and dimensional uniformity.

13 of 65
Table 4 Suggested Starting Conditions for Processing Durethan Resins

BC 30 BKV 15 / 30 / 40 / 50
B 30 S BC 40SR2 BKV 115 / 130 / 140
Conditions B 31 SK BC 304 BM 30X / 40X

Processing Temperatures
Zones
Rear 470°– 480°F (245°–250°C) 490°–500°F (255°–260°C) 470°–480°F (245°–250°C)
Middle 480°–500°F (250°–260°C) 500°–520°F (260°–270°C) 480°–510°F (250°–265°C)
Front 500°– 520°F (260°–270°C) 520°–535°F (270°–280°C) 510°–535°F (265°–280°C)
Nozzle 500°– 520°F (260°–270°C) 520°–550°F (270°–290°C) 520°–550°F (270°–290°C)
Melt * 480°–520°F (250°–270°C) 520°–550°F (270°–290°C) 520°–550°F (270°–290°C)
Mold ** 175°– 250°F ( 75°–120°C) 160°–195°F ( 70°– 90°C) 160°–230°F ( 70°–110°C)

Machine Conditions
Injection
10,000 –20,000 psi (70 –140 MPa)
Pressure
Hold
50% of Injection Pressure
Pressure
Back
50 –150 psi (345 –1,035 kPa)
Pressure
Injection
Moderate to Fast
Speed
Injection
0.125 – 0.250 in. (3 – 6 mm)
Cushion
Screw Speed 60 – 100 rpm
Clamp
2 – 4 t / in.2 ( 22–55 kPa)
Tonnage

* To obtain proper melt temperature, take an air shot and measure the melt with a heated pyrometer probe.
** Check mold temperature on the part cavity and core surface.

14 of 65
 DRYING

MATERIAL HANDLING DRYING EQUIPMENT cylindrical and has a diverter cone and
baffles to diffuse the air uniformly and
Even though Durethan polyamide is Use a desiccant dehumidifying hopper retard channeling of the pellets. The
supplied in sealed, moisture-tight, dryer to remove moisture from hopper must be capable of holding
multi-walled bags, dried and ready for Durethan resin and to maintain proper 4 times the output per hour of the
processing, use a desiccant dehumidify- resin moisture content levels during injection molding machine. This will
ing hopper dryer to keep the resin dry processing. A typical dessicant dehu- ensure that the resin remains in the
during processing. Moisture-contam- midifying hopper dryer system and air- drying hopper at least 4 hours.
inated resin may lead to processing flow are shown in Figures 12 and 13.
problems and affect the surface finish Note that the drying hopper is tall and The use of a vented-barrel molding
of the part. machine is not recommended for
Durethan polyamides because the
Warm to room temperature any sealed molten resin can discolor from contact
bags that have been stored in an un- with the oxygen in the air that is present
heated warehouse before opening them. at the vent.
This will help prevent rapid condensa-
tion of ambient moisture on cool
pellets. Figure 12 Typical Desiccant Dehumidifying Hopper Dryer System

Single bags can take up to 24 hours to

warm up. Stacked bags, pallets, or
boxes can take up to a week to reach
ambient temperatures.

When exposed to atmospheric moisture,

most grades of Durethan resin will
absorb moisture at levels beyond the
preferred limit of less than 0.10% in
less than an hour. Therefore, prevent
exposing the resin to undried air, and
once a bag is opened, dry exposed resin
prior to processing.

15 of 65
DRYING CONDITIONS ● Dew point of the inlet air to the periodically monitor the moisture
hopper: 0°F (-18°C) or less. content of the inlet air throughout
Observe the following drying condi- the molding operation.
tions for proper moisture removal from ● Airflow to the hopper: 1.0 cubic foot
Durethan polyamide resins: per minute (CFM) for every pound of If the resin being processed comes
resin per hour of throughput. from an opened container and/or
● Drying inlet air temperature to the contains regrind or color concentrate,
hopper: 170°–180°F (77°–82°C). The acceptable moisture content of the time required to adequately dry
Drying temperatures above 180°F Durethan resin to ensure optimum it for processing may be as long as
(82°C) may cause material property performance is less than 72 hours.
discoloration. 0.10%. Use a dew-point meter to

Figure 13 Desiccant Dehumidifying Hopper Dryer System Airflow

16 of 65
 DRYING, continued

Table 5 Dehumidifying Hopper Dryer Troubleshooting Guide

Improper Drying Condition Possible Causes Possible Corrective Action

Poor Dew Point ● Dirty filter(s). ● Clean or replace filter(s).

(Check inlet air hopper with a dew-point ● ●
Saturated desiccant. Dry-cycle machine for several complete
meter, the only sure way to check dry-
cycles. Saturated desiccant is a common
ness. A dew point greater than 0°F/
problem with machines that are not in
-18°C is poor.)
continuous use.
● Excessive return air temperature. ● Add after-cooler on return air line.
● Burned-out heater(s). ● Repair or replace heater(s).
● Contaminated or worn-out desiccant. ● Replace desiccant.
● Bad heater thermostat or thermocouple. ● Repair or replace thermostat or
thermocouple.
● Malfunctioning regeneration cycle timer. ● Adjust or replace timer.
● Air control butterfly valves not seating. ● Adjust valve seating.

Material Residence Time in Hopper ● Dryer hopper too small for the amount of ● Use a larger dryer hopper.
Too Short material being processed per hour.
● Not keeping hopper at least 2 / 3 filled. ● Keep drying hopper full.
● Moist room air leaking into the dry ● Check all hose connections and tighten
process air. as required. Check all hoses for leaks and
replace as needed. Check filter covers for
secure fit and tighten as required.

Incorrect Process Air Temperature ● Incorrect drying air temperature. ● Dial in correct temperature
(170°–180 °F / 77°– 82°C).
● Dryer temperature controller malfunction. ● Repair or replace controller.
● Thermocouple malfunction. ● Repair or replace thermocouple.
● Faulty process air heating elements. ● Repair or replace heating elements.
● Supply voltage different than required ● Check supply voltage against name-
heater voltage. plate voltage.
● Non-insulated inlet air hose. ● Repair or replace inlet-air hose.
● Excessive changeover temperature. ● Increase reactivation airflow.

Insufficient Inlet Airflow ● Dirty or clogged filter. ● Clean or replace filters.

(Good dew point but resin still wet.) ● ●
Incorrect blower rotation. Change blower rotation. (See equipment
manufacturer’s electrical instructions ).
● Obstruction in air ducts. ● Remove air duct obstruction.

17 of 65
 INJECTION MOLDING

Optimizing the injection molding The following processing data were Processing parameters that optimize
process involves several variables: obtained over a long period on a vari- the appearance of a molded part can be
ety of molding machines and molded easily determined. However, these
● Ratio of heat transferred by external parts. They represent the range for same settings may not give the part its
heaters to frictional heat. initial processing settings to be used optimum dimensions or shape. When
during start-up and may need adjust- molding parts which must hold to crit-
● Injection speed and pressure. ment to meet the requirements of ical dimensional tolerances, conduct
individual parts. a statistical study to optimize both
● Holding pressure and time. dimensions and appearance. Then
adjust certain processing parameters
● Cooling time. to change part dimensions as required.

● Mold temperature.

Figure 14 Temperature Zones / Machine Cross Section

18 of 65
 INJECTION MOLDING, continued

TYPICAL PROCESSING TEMPERATURES

Table 6a Barrel Heating Temperatures for Durethan Resin

Processing B 30 S BC 30 BKV 15 / 30 / 40 / 50 Barrel Heating Zones

Temperature B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
Zones
The initial barrel temperature ranges are
approximate and can vary, depending
Rear 470°–480° F 490°–500°F 470°–480°F
(245°–250°C) (255°–260°C) (245°–250°C) on screw geometry, frictional heating,
Middle 480°–500°F 500°–520°F 480°–510°F cycle time, and material flow length.
(250°–260°C) (260°–270°C) (250°– 265°C) Higher-viscosity and glass-fiber-rein-
500°–520°F 520°–535°F 510°–535°F forced grades require settings near the
Front
(260°–270°C) (270°–280°C) (265°–280°C)
upper limits of the range. In all cases,
however, the temperature profile should
increase incrementally from the rear of
the barrel to the nozzle.

Take care to maintain a consistent melt

temperature and inspect the heater bands
periodically. Durethan resins are sensi-
tive to overheating or remaining in the
melt phase for a prolonged time. Do not
exceed a maximum melt temperature of
550°F (290°C) for any grade of
Durethan resin.

Table 6b Nozzle Temperatures for Durethan Resin

Nozzle
Processing B 30 S BC 30 BKV 15 / 30 / 40 / 50
Temperature B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
It is important that the nozzle be
500°–520° F 520°–550°F 520°–550°F
Nozzle equipped with an independent heating
(260°– 270°C) (270°–290°C) (270°–290°C)
system and controller to maintain a
constant melt temperature. In most
cases, the optimum nozzle temperature
is below the front zone temperature, in
the range of 500°–520°F (260°– 290°C).

19 of 65
Table 6c Melt Temperatures for Durethan Resin

Processing B 30 S BC 30 BKV 15 / 30 / 40 / 50 Melt Temperature

Temperature B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
The optimum melt temperature for most
480°–520° F 520°–550°F 520°–550°F
MELT* parts is in the range of 480°–550°F
(250°– 270°C) (270°–290°C) (270°–290°C)

* To obtain the proper melt temperature, take an air shot

(250°–290°C). Lower melt tempera-
and measure the melt with a heated pyrometer probe. tures can minimize drool while higher
melt temperatures can assist in filling
complicated parts or parts with thin
walls.

Check the actual temperature of the melt

at the nozzle from an air shot and
correct the nozzle controller settings
accordingly. To obtain an accurate melt
temperature measurement, make an air
shot from a normal processing cycle and
immediately place a preheated thermo-
couple probe into the center of the melt.
Keep it in the melt until the maximum
temperature is reached (see Figure 15).

Making an Accurate Melt

Figure 14 Temperature Reading

To obtain an accurate melt temperature for adjusting the

controller settings, make an air shot from a normal processing
cycle. Immediately insert the temperature probe into the center
of the melt until the maximum temperature is reached.

20 of 65
 INJECTION MOLDING, continued

MACHINE CONDITIONS

Table 7a Injection Pressure for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Injection Pressure

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
The injection of molten Durethan resin
Injection
Pressure
10,000 – 20,000 psi 10,000 – 20,000 psi 10,000 – 20,000 psi into a mold is usually done in two phases:
the primary, injection phase and the
secondary, hold phase. In the injection
phase, the melt is rapidly injected into
the mold at a pressure of 10,000 – 20,000
psi (70 – 140 MPa) until the mold is just
filled.

Too little injection pressure may not fill

the mold completely with resin. Too
much injection pressure can lead to flash
and overpacking. The injection pressure
also influences surface quality and
orientation. Therefore, use only enough
pressure to fill the mold.

Table 7b Hold Pressure for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Hold Pressure

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
Ideally, the secondary or hold pressure
Hold 50% Injection 50% Injection 50% Injection
Pressure Pressure Pressure Pressure should be 50%– 60% of the primary,
injection pressure — just high enough
to prevent sinks and voids.

The hold phase packs out the mold and

compresses the material to the proper
density. Packing produces mold textures,
eliminates sinks and voids, and estab-
lishes internal orientation. Overpacking
during this phase can lead to flash,
shrinkage and warpage problems, and
part ejection problems.

21 of 65
Table 7c Injection Speed for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Injection Speed

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
Durethan resin requires a rapid injection
Injection
Moderate to Fast Moderate to Fast Moderate to Fast speed. If the injection speed is too slow,
Speed
the flow front can cool down and begin
to solidify. This prevents satisfactory
mixing of flow fronts after flowing
around an insert or hole, for example,
which can show up in the finished parts
as pronounced weld lines. Weld line
strength can be diminished. Slow
injection speed can also reduce surface
quality.

A slow or graduated injection speed may

be necessary when the melt stream does
not encounter a wall as it enters the
cavity. Otherwise, the material can spray
the length of the mold (jetting) then fill in
irregularly around this mass.

Table 7d Injection Cushion for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Injection Cushion

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
A slight cushion of 0.125 – 0.250 in.
Injection
0.125 – 0.250 in. 0.125 – 0.250 in. 0.125 – 0.250 in. (3– 6 mm) is suggested. Without a slight
Cushion
cushion the screw may bottom out and
prevent complete packing of the mold.
Too much cushion may lead to longer
time in the barrel and material degrada-
tion. Any fluctuation in the amount of
cushion, once it has been set, is an in-
dication that either the screw is slipping
or the non-return valve is allowing resin
to back-flow.

22 of 65
 INJECTION MOLDING, continued

Table 7e Back Pressure for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Back Pressure

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
The function of back pressure is to
Back
50 – 150 psi 50 – 150 psi 50 – 150 psi control shear heating and improve melt
Pressure
uniformity. It also removes any air drawn
in with the pellets.

Set the nominal back pressure at 50–

150 psi (345–1,035 kPa). Back pressure
that is too low may cause inconsistent
feeding and trapped air. During injection,
this air is compressed and heated, causing
black or brown degradation and bubbles
in the part. Back pressure that is too high
may cause thermal damage to the mate-
rial through over-shearing. With filled
resin grades, high back pressure can
cause excessive fiberglass breakage.

Table 7f Screw Speed for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Screw Speed

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
Screw
The recommended screw speed for
60 – 100 rpm 60 – 100 rpm 60 – 100 rpm
Speed Durethan resin is 60 –100 revolutions per
minute (rpm).

A slow screw speed provides a more uni-

form temperature distribution than can be
achieved with a high screw speed by pro-
viding enough time for heat to be intro-
duced through the cylinder wall of the
injection molding machine and conducted
across the cross-section of the screw
channel.

23 of 65
 However, a screw speed that is too slow
can lead to long cycles and poor shear
heating. A screw speed that is too fast
can lead to excessive shear heating which
may degrade the resin melt and cause
discoloration.

Allow the screw to rotate until just before

the mold opens.

Table 7g Clamp Tonnage for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Clamp Tonnage

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
Properly matching the size of the injec-
Clamp
2 – 4 t / in.2 2 – 4 t / in.2 2 – 4 t / in.2 tion molding machine to the part to be
Tonnage
molded is very important. A clamp ton-
nage of 2– 4 t/in.2 (25– 55 kPa) of
projected part surface area is required
to prevent the mold from blowing open
and causing flash.

Table 8 Mold Temperature for Durethan Resin

Machine B 30 S BC 30 BKV 15 / 30 / 40 / 50 Mold Temperature

Conditions B 31 SK BC 40SR2 BKV 115 / 130 / 140
BC 304 BM 30X / 40X
Even when optimally molded, crystalline
Mold 175° – 250° F 160° – 195° F 160° – 230° F
Temperature* (75° – 120° C) (70° – 90° C) (70° – 110° C) resins such as Durethan resins contain a
substantially amorphous fraction. (This is
* Check the mold temperature on the part cavity and core surface.
why crystalline resins are also referred to
as semi-crystalline.) Properties of the part
depend on the crystalline-to-amorphous
ratio, which is determined by the temper-
ature of the mold and rate of cooling.
Therefore, molding conditions, especially
mold temperature, must be carefully
chosen and maintained to ensure consis-
tent part quality.

24 of 65
 INJECTION MOLDING, continued

While low mold temperatures result in Mold Temperature Control mold temperature. The fluid can be
rapid cooling and high output rates, the heated to raise the temperature of the
quality of the parts is adversely affected. Melts of Durethan resin must be injected mold, and it can remove heat given off
The degree of orientation, internal into hot molds to help ensure the quality by the plastic melt as it cools.
stresses, and post-shrinkage increase, of the molded part. Internal stresses,
and surface quality is reduced. Rapid shrinkage, dimensional tolerance, sur- Electrical resistance heaters (cartridge
cooling can cause the formation of an face quality, and mechanical properties heaters) provide an effective way to
amorphous outer layer which can reduce — all are influenced by the temperature maintain elevated mold temperatures.
the physical properties and chemical of the mold. The cartridges are inserted into wells
resistance of the part. High mold tem- cut in the mold and controlled by
perature and slow cooling, however, Maintain a uniform temperature across external rheostats.
result in higher crystallinity, better the mold surface and between the cavity
dimensional control, better properties, and core to allow the molded part to Circulating heat transfer fluids are pre-
and better chemical resistance. shrink uniformly and thus avoid distor- ferred to electric cartridge heaters
tion and variations in dimensional toler- because they can readily add or remove
Recommended mold temperatures for ances. To achieve this, adjust the cool- heat as required. The fluid is easy to
various grades of Durethan B resin are ant flow rates, coolant temperature, and pump, provides very efficient heat
provided in Table 8. Check the tem- cooling circuit to provide maximum transfer, and can be circulated in areas
perature of the mold on the part cavity cooling to the hottest areas. that are often inaccessible to electric
and core surfaces rather than relying on cartridge heaters. The use of heat
mold temperature control settings (see Circulating a heat transfer fluid through transfer fluids also aids in achieving
Figure 16). Set the temperature on the channels cut into the mold body is one a consistent mold temperature over
stationary half of the mold different than effective way to control and maintain extended production runs.
the moving half of the mold to control
warpage in a molded part.

Variation in the Temperature of the

Measuring Mold Surface Temperature Mold Surface During the Injection
Figure 16 During the Injection Molding Cycle Molding Cycle Figure 17
MOLD SURFACE TEMPERATURE (T)

Injection Ejection
➤

Tmax
T = 5 – 20°C ➤

Tav

Tmin
➤

➤
➤ tk ➤
tCycle ➤

TIME (t)

25 of 65
Regardless of which type of heater is can be achieved simply by insulating more restricted circuit will be too
used, a separate controller for each half the mold halves from the platens. low.
of the mold is desirable because it is
sometimes necessary to operate the core Following are some additional ways to ● Install filters in front of the mold inlet
half of the mold at a slightly lower tem- improve temperature control: to control fluid contamination.
perature than the cavity half. This helps
retain the part on the core when the ● Match fluid circulator capacity to the ● Match electric cartridge size and
mold is opened, aiding in part removal. size of the mold. quantity to the size of the mold.
Some complicated molds with large
lifters and cams may require additional ● Place sheets of insulating material ● Minimize the time the mold is open
control zones. between mold halves and platens. during the molding cycle.

Considering the high mold temperatures ● Clean out rust and scale periodically ● Use bubblers and heat pipes to dis-
achieved in processing Durethan resin, from cooling channels. place additional heat from the mold.
observe all precautions recommended
by the manufacturer of the heat transfer ● Use conditioned water or other heat
system. Use shielded hoses and auto- transfer fluids. Residence Time
matic shut-off fittings, and secure the
fastening of all the fittings to avoid ● Use high coolant throughput rates to It is recommended that Durethan resin
spills, leaks, and operator injury. maintain turbulent flow and efficient remain in the barrel at a melt tempera-
cooling. ture of 535°F (280°C) for no more than
The temperature of the mold surface 30 minutes. High temperatures
can vary as much as 36°F (20°C) dur- ● Avoid unbalanced parallel cooling necessitate shorter residence times as
ing the injection molding cycle. Mini- circuits because flow rate through a do certain additives and coolants.
mizing wide temperature fluctuations

Effect of Part Wall Thickness on Total Mold Cycle Time

at Various Mold and Melt Temperatures, °F (°C) Figure 18
70

60 250 °/ 535° F
195°/520° F (120°/280°C)
Unreinforced Resin (90°/270° Reinforced Resin
50 Melt/ Mold Temperature C) Melt /Mold Temperature 210°/520° F
175°/490° F (100°/270° C)
40 (80°/255° C)
175°/ 500° F
160°/ 465°F (80°/260° C)
COOLING TIME, sec

30 (70°/240° C)

20

10

0
0 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0 0.04 0.08 0.12 0.16 0.20 0.24 0.28
(1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7)

WALL THICKNESS, in. (mm)

26 of 65
 INJECTION MOLDING, continued

Cycle Time PART SHRINKAGE ● Increasing the holding time decreases

shrinkage.
The optimum cycle to produce quality Thermoplastics shrink after filling a
parts includes a fast fill, a hold time just mold cavity due to contraction as the These effects on unfilled Durethan
long enough for the gates to freeze, and melt cools. Crystalline plastics such as resins are shown graphically in
a cooling time long enough that the part some polyamides will shrink an addi- Figure 19.
ejectors do not penetrate the part. tional amount as the polymer chains
Cooling time is the major portion of the order themselves into compact crystal- Fiberglass-reinforced Durethan resin
total molding cycle. The cooling time line regions. Fillers and other additives exhibits more complex shrinkage
required for a part depends on its wall influence shrinkage to varying degrees. behavior. During injection molding the
thickness (see Figure 18), runner size, individual fibers tend to align in the
and sprue size. Normally, faster cycles Various molding process parameters direction of flow. They restrict the
are achieved with glass- and mineral- also influence shrinkage. For example: shrinkage of the plastic, the effect being
reinforced resins than with unreinforced greater in the flow direction than in the
resins. ● Increasing the melt temperature cross-flow direction. While typical
decreases shrinkage. shrinkage values for unfilled Durethan
resins are 1.0% – 1.4% in both direc-
MOLD RELEASE AGENTS ● Increasing the mold temperature tions, the typical shrinkage values for
increases shrinkage. 30% glass-fiber-reinforced Durethan
Mold lubrication may be a good idea resin are about 0.3% in the flow
for start-up shots. Mold release agents ● Increasing the injection rate increases direction and 0.9% in the cross-flow
intended for high-temperature molds are shrinkage. direction.
recommended. Avoid using silicone
lubricants for molding parts with ● Increasing the holding pressure
Durethan resin which will be used for decreases shrinkage.
electronic applications because they
Effect of Process Conditions on Shrinkage with
may affect the end-use performance of Figure 19 Non-Reinforced Grades of Durethan Resin
the device.
Shrinkage (%)

If you are experiencing a problem with

parts sticking to the mold, consult a
LANXESS Corporation technical
representative for Durethan resin at Dwell Time Holding Pressure Injection Pressure
Shrinkage (%)

800-LANXESS to help you determine

the best solution.

Mold Temperature Melt Temperature Injection Speed

Across Flow Direction In Flow Direction

27 of 65
The difference in flow versus cross- forces. Therefore, keeping part shrink- thoroughly blended with the virgin
flow shrinkage can cause warping in age to a minimum can control the resin prior to drying and processing.
molded parts. Proper part and mold amount of frictional force and reduce
design achieved with the aid of mold the adhesion of the part to its mold. Under no circumstances should de-
filling analysis programs can reduce graded, discolored, or contaminated
this effect. material be used for regrind. Discard
COLOR CONCENTRATES such materials.
For more information, refer to the
LANXESS Corporation publication, Coloring Durethan polyamide can be Improperly mixed and/or dried resin
Part and Mold Design-Thermaplastics, accomplished by blending with concen- may diminish the desired properties of
or consult a LANXESS Corporation trates from either LANXESS or other Durethan resin. You must conduct test-
technical representative for Durethan commercial sources. Thoroughly blend ing on finished parts produced with any
resin at 800-LANXESS. the color concentrate with the virgin resin amount of regrind to ensure that your
and properly dry the mixture prior to end-use performance requirements are
introducing it to the molding machine. fully met. Regulatory agencies and / or
PART EJECTION organizations, e.g., Underwriters
When using commercial color concen- Laboratories (UL), may have specific
The ejection of a part from a mold is trates, take care to ensure that the color
affected by the surface quality of the carrier is polyamide.
mold core, the adhesion of the part to
the core, and by the shape of the part.
While the surface quality of the mold USING REGRIND
Figure 20 Regrind Material
core and the shape of the part cannot
be controlled by varying the processing Up to 10% regrind may be used with all
parameters, the adhesion of the part to grades of virgin Durethan polyamide
the core can be controlled. resin, depending upon the end-use
requirements of the molded part and
The adhesion of a part to the mold core provided that the material is kept free
is a result of friction between the part of contamination and is properly dried
and the mold surface. Material shrink- (170°– 180°F/77°– 82°C for 4 or more
age on to the core increases frictional hours). (See “Drying,” page 15, for Recommended grinder screen size is
details.) Any regrind used must be 0.31 in. (8 mm).
generated from properly molded parts,
sprues, and/or runners. All regrind used
must be clean, uncontaminated, and

28 of 65
 INJECTION MOLDING, continued

requirements limiting the allowable POST-MOLD CONDITIONING Since some applications require high
amount of regrind. LANXES elongation for immediate assembly, or
does not recommend the use of third- The moisture content of parts molded high impact resistance in order to be
party regrind because it generally does of Durethan resin affects various put into immediate service, it is desir-
not have a traceable heat history, nor properties. Rigidity and strength both able to quickly increase the moisture
does it offer any assurance that proper decrease with increasing moisture content of parts molded of Durethan
temperatures, conditions, and/or content, while elongation and impact resin. This can be done by moisturizing/
materials were used in processing. Use strength increase with increasing conditioning the parts above the equi-
extreme caution when buying and using moisture content. Moisture absorption librium moisture content level for the
third-party regrind. from the atmosphere is dependent upon Durethan polyamide grade before the
temperature, relative humidity, and the parts’ assembly or use. Any excess
Avoid using regrind material entirely part wall thickness, and the process is moisture will be lost to the atmosphere
when resin properties equivalent to usually slow. or redistributed internally.
virgin material are required, includ-
ing, but not limited to, color quality, One way of accelerating the moisturiz-
impact strength, resin purity, and/or ing/conditioning of parts molded of
load-bearing performance. Durethan resin is to place them in a

Moisture Absorption Rate of Parts Water Absorption by Non-Reinforced

Molded of Durethan B Resin, Durethan B Resin Immersed in Water
Exposed to a “Tropical Environment” at 140°F (60°C) as a Function of Wall
of 95% – 98% RH at 105°F (40°C) Figure 21 Thickness and Time Figure 22

8
8
t

6
en
on

6
nt
pti

Co
or

n
WALL THICKNESS (mm)
WALL THICKNESS (mm)

tio
bs

er

ra
at
rA

tu
W

4 4
ate

Sa
3%
W
3%

2 2

0 0
2 4 6 8102 2 4 6 8 103 2 4 6 2 4 6 8 10 2 4 6 8 102 2 4 6

HOURS HOURS

29 of 65
 “tropical” environment of 95% RH introduces some moisture into the part, Conditioning differs for parts molded of
at 105°F (40°C). Exposure time is it is not as effective as “tropical” unreinforced and reinforced Durethan
dependent upon part wall thickness and conditioning because only the outer resins.
the desired level of conditioning, which portions of the part are conditioned. It
is determined by end-use performance takes a relatively long time for the water
requirements. to migrate inward. Unreinforced

Another, more common method of con- Moisture uptake rates for both “tropi- Figure 23 shows the moisture absorp-
ditioning is to immerse the parts in cal” conditioning and immersion tion rate of parts molded of unrein-
water at 140°– 176°F (60°– 80°C). conditioning are shown in Figures 21 forced Durethan resin having various
However, while this method quickly and 22. wall thicknesses when stored in a

Water Absorption by Non-Reinforced

Durethan B Resin When Stored in a Equilibrium Moisture Content
Standard Atmosphere of DIN 50014 of Durethan B Resin as a Function
as a Function of Wall Thickness of Relative Humidity, Measured at
and Time Figure 23 Room Temperature Figure 24
11

2.0 10
EQULIBRIUM WATER CONTENT (%)

9
8
1.5
t
ten

7
on
rC

sin
WALL THICKNESS (mm)

6
Re
ate

1.0 5 B
W

n
ha
3%

4 ret
Du
3
0.5
2
1
0
100 2 4 6 8 101 2 4 6 8 102 2 4 6 8 0 10 20 30 40 50 60 70 80 90 100

DAYS RELATIVE HUMIDITY (%)

30 of 65
 INJECTION MOLDING, continued

standard test environment of 73°F directly related to the ambient temper- Reinforced
(23°C) and 50% relative humidity. The ature and relative humidity, as shown in
material was brought to the desired level Figure 24. The mechanical properties of parts
of conditioning to properly determine molded of filled or reinforced Durethan
potential property performance accord- During conditioning, moisture absorp- resins are less dependent upon moisture
ing to DIN 50014. tion will enlarge the part and cause a content. If conditioning is required, use
change in dimensions. An example is approximately the same conditioning
Wall thickness strongly influences the shown in Figure 25. Therefore, a parameters used for parts molded of
length of time required to attain equi- balance must be achieved between unreinforced Durethan resins.
librium moisture content. The equilib- the level of end-use performance and
rium moisture content of a part is dimensional accuracy required. The equilibrium moisture content is
lower for parts molded of reinforced
Durethan resin grades than for parts
molded of unreinforced grades. For
example, parts molded of 30% glass-
Linear Change in Length of Rectangular Bars Injection reinforced BKV 30 resin have approx-
Molded in Various Grades of Durethan B Resin as a
imately 1.5% equilibrium moisture
Function of Water Content* Figure 25
content in a standard atmosphere versus
3
3.0% for a typical unfilled grade at the
same conditions.

Avoid conditioning temperatures higher

than 140°F (60°C) for parts molded of
2
reinforced Durethan resins. Prolonged
exposure to hot water can adversely
affect the bond between the resin and
reinforcement.
CHANGE IN LENGTH (%)

0
0 1 2 3 4 5 6 7 8 9 10

WATER CONTENT (%)

* Length of injection molded rectangular bars 120 x 10 x 4 mm in various

grades of Durethan B resin as a function of water content. Storage
temperature: 20°C. The curve represents average values derived from
numerous measurements.

31 of 65
The dimensional change of parts mold- Another method is mechanical clean- manufacturer's MSDS safety recom-
ed of reinforced Durethan resins after ing, as shown in Figure 26. It is more mendations) after it has cooled.
conditioning is less than that of parts thorough than purging and can be used
molded of unreinforced resins. The either prior to running Durethan resin or 4. Once the nozzle has been removed,
exact amount depends on the level of upon the completion of a run. Follow turn off the heat in the main cylinder
reinforcement. these steps: and push the screw forward until a
few flights are exposed.
For more information on post-mold 1. Flush the cylinder rapidly with
conditioning parts molded of Durethan polystyrene. 5. Remove the hot melt from the screw
resin, consult the LANXESS publication, with a brass brush and a brass knife.
Durethan Polyamide — Environmental 2. Remove the nozzle while keeping Push the screw forward and clean it
Conditioning, which can be obtained the heat on in the main cylinder. in this way until all of the flights are
from LANXESS Corporation by clean.
contacting a LANXESS technical 3. Clean the nozzle either by heating it
representative for Durethan resin in a muffle furnace or by soaking it 6. Remove the screw and clean the
at 800-LANXESS. in an appropriate solvent (follow barrel with a rotary-type brush on an
extension rod attached to an electric
drill.
MACHINE PREPARATION
Purging and Cleaning

An essential requirement for molding Mechanical Cleaning of the Screw

Figure 25
the highest-quality parts with Durethan
resin is a cylinder that is completely free
of any residual polymer from a previous
run. Deposits of residual material can
loosen and contaminate the Durethan
polyamide.

One method of removing residual mate-

rial from the molding machine is to
purge it with general-purpose polysty-
rene (PS) or a similar high-tempera-
ture purging compound.

Follow the purging material manufac-

turer’s guidelines for use.

32 of 65
 INJECTION MOLDING, continued

START-UP PROCEDURE SHUTDOWN PROCEDURE ● Move the screw forward.

Suggested starting conditions for Shut down the molding machine at the ● Lower all heat zones on the cylinder
processing Durethan resins are provided end of a production run according to the and nozzle to 300°F (150°C).
in Table 9. Allow enough machine heat- procedure for either a short- or long-
up time for the barrel to reach molding term shutdown. Observing proper
temperatures for at least 1/2 hour before shutdown procedure is important to Long-Term Shutdown
rotating the screw or feeding pellets. prepare the machine to restart produc-
Then make several initial short shots tion and to avoid material or machine For shutdowns exceeding 5 hours or
with less than maximum injection pres- problems during future start-ups. For extending to several days:
sure to prevent overpacking. Overpack- example, if a full barrel of Durethan
ing can make part removal difficult. polyamide is allowed to cool and shrink ● Shut off the hopper feed.
After the initial short shots, increase inside the molding machine, it may pull
injection pressure and speed, shot particles of poorly adhered chrome from ● Flush the machine with general-
weight, and melt temperature until the the surface of the screw. These particles purpose polystyrene and purge it
mold is properly filled. would contaminate future moldings. empty.

● Leave the screw forward in the

Short-Term Shutdown cylinder.

For short-term production breaks of ● Turn off all heat zones.

less than 30 minutes, purge the cylinder
upon start-up and continue molding.
For shutdowns limited to a period of
2 – 5 hours:

● Shut off the hopper feed.

● Purge the machine empty, or make

shots until no material remains in the
machine.

33 of 65
Table 9 Suggested Starting Conditions for Processing Durethan Resins

BC 30 BKV 15 / 30 / 40 / 50
B 30 S BC 40SR2 BKV 115 / 130 / 140
Conditions B 31 SK BC 304 BM 30X / 40X

Processing Temperatures
Zones
Rear 470°– 480°F (245°–250°C) 490°–500°F (255°–260°C) 470°–480°F (245°–250°C)
Middle 480°–500°F (250°–260°C) 500°–520°F (260°–270°C) 480°–510°F (250°–265°C)
Front 500°– 520°F (260°–270°C) 520°–535°F (270°–280°C) 510°–535°F (265°–280°C)
Nozzle 500°– 520°F (260°–270°C) 520°–550°F (270°–290°C) 520°–550°F (270°–290°C)
Melt * 480°–520°F (250°–270°C) 520°–550°F (270°–290°C) 520°–550°F (270°–290°C)
Mold ** 175°– 250°F ( 75°–120°C) 160°–195°F ( 70°– 90°C) 160°–230°F ( 70°–110°C)

Machine Conditions
Injection
10,000 –20,000 psi (70 –140 MPa)
Pressure
Hold
50% of Injection Pressure
Pressure
Back
50 –150 psi (345 –1,035 kPa)
Pressure
Injection
Moderate to Fast
Speed
Injection
0.125 – 0.250 in. (3 – 6 mm)
Cushion
Screw Speed 60 – 100 rpm
Clamp
2 – 4 t / in.2 ( 22–55 kPa)
Tonnage

* To obtain proper melt temperature, take an air shot and measure the melt with a heated pyrometer probe.
** Check mold temperature on the part cavity and core surface.

34 of 65
 TOOLING

The information in this section is pre- MOLD DESIGN Venting

sented as an overview. Detailed infor- Material Selection
mation is available in the LANXESS Mold venting is particularly important
Corporation publication, Part and As with other filled engineering resins, for fast-filling materials like Durethan
Mold Design-Thermoplastics, which it is recommended that production resin. As a mold cavity fills, the air
can be obtained by contacting a molds made from hardened tool steels being displaced by the molten resin
technical representative for such as A-2, A-6, S7, HB or D-2 be must have a way out of the tool. Vent-
Durethan resin at 800-LANXESS. used with Durethan resins. ing enables the displaced air to easily
escape from the mold. This permits
faster filling, prevents material burns
Surface Finish and deterioration of the cavity sur-
faces, and results in stronger weld lines.
A variety of tool surfaces such as
chrome, electroless nickel, boron, or Recommended vent dimensions are
nitride have been used successfully 0.0005 –0.0015 in. (0.015– 0.040 mm)
with Durethan polyamide resins, deep by 0.25–0.75 in. (6–19 mm)
depending upon the end-use wide. At a distance of 0.15–0.30 in.
requirements of the molded part. (4–8 mm) from the cavity, vent
channels should be deepened to 0.04 in.
The standard finish for most molds is (1.0 mm) or more (see Figure 27).
SPE/SPI #2.

Figure 27 Vent Depth Figure 28 Vent Placement

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Typical Vent Depth “D” Range for Durethan Resins

0.0005 - 0.0015 in. Typical Applications
0.0005 - 0.0010 in. Applications Requiring
Minimal Finish

35 of 65
Part Draft Weld Lines Tolerances

The walls of parts molded of Durethan Weld lines are created wherever two Tight-tolerance molding can be accom-
resin require 1° of draft per side in the flow fronts come together in the mold plished with good machine controls.
direction of draw to aid part ejection cavity during injection of the resin The amount of cross-flow shrinkage in
from the tool, subject to the functional melt. With glass-reinforced grades of reinforced grades of Durethan resin is
requirements of the part (see Figure Durethan resin, the glass fibers do not typically several times greater than the
29). Glass-fiber-reinforced nylon intermingle well at the flow fronts, shrinkage in the flow direction. Con-
shrinks less than standard resin grades creating an area of reduced strength. sider flow orientation when assigning
and requires draft angles of 1°– 2.° Try to locate any weld lines away from and evaluating tolerances.
areas of the part requiring full material
strength.
Texturing MOLD TYPES
2- or 3-Plate Molds
Typically, the surface texture of the Undercuts
mold depends upon the end-use The selection of either two- or three-
requirements of the finished part. Some Undercuts can make it difficult to re- plate mold construction for processing
textures are unsuitable for filled resins. move parts from the mold. Therefore, Durethan resin is usually determined by
Textured surfaces require an additional avoid undercuts, especially when using part geometry, production volume,
draft of 1° for every 0.001 in. (0.025 glass-fiber-reinforced Durethan resin scrap considerations, cosmetics, and
mm) depth of texturing. because of its high rigidity. cost. The resin’s property performance
potential is not a determining factor.

Figure 29 Draft Figure 30 Sprue Design

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36 of 65
 TOOLING, continued

Single- and Multi-Cavity Molds Sprue Bushings Sprue Pullers

Durethan resin can be successfully Use sprue bushings having a taper of Use sprue pullers of any common
processed in both single- and multi- 0.5 in./ft (0.42 mm/cm) and an orifice design, but avoid any that restrict the
cavity molds. Which type is used is (small end) diameter of 0.125 – 0.375 flow of the material. A 5° reverse-taper
dictated by the complexity of the part in. (3.2 – 9.5 mm), depending on the sprue puller, as shown in Figure 31,
and the required production volume. size of the molding. The spherical ra- works well.
dius of the bushing should be equal to
or, preferably, slightly larger than that Cold-slug wells are recommended and
SPRUE CONSIDERATIONS of the nozzle. The nozzle discharge should be built into the base of the
opening must not exceed the diameter sprue and at every branch or sharp turn
The size of the sprue is determined by of the sprue bushing inlet to avoid in the runner system. This provides a
the size of the shot and the molding forming an undercut that could stick the trap for cold, solidified material, keep-
machine to be used. Keep the sprue sprue. To promote flow, the sprue inlet ing it out of the cavity.
highly polished to facilitate easy opening should be about 20% larger
removal from the stationary half of than the nozzle orifice. A generous
the mold. radius of 0.02 – 0.08 in. (0.5 – 2.0 mm)
is recommended at the transition from
the sprue into the runner system or the
mold cavity (see Figure 30).

Figure 31 3PRUE 0ULLERS

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37 of 65
RUNNERS AND RUNNER Hot Runner Molds GATING
SYSTEMS
It is possible to use hot runner molds Gate type and location are determined
Keep runners as short as possible to with Durethan resins. However, the low by the part design. Any of the gating
reduce unnecessary pressure drops be- melt viscosity can cause drooling or styles typically used in injection mold-
tween the sprue and gate. Full-round nozzle tip freeze-off problems. Proper ing can be used successfully with
cross sections are best. design of the hot drop tip area is crucial Durethan resin.
for Durethan resins. Consult the hot
It is essential that the runner system be runner supplier’s technical staff when Regardless of the type employed, locate
balanced to ensure uniform filling of all selecting a system for Durethan poly- the gate in the thickest section possible
cavities, especially for precision parts. amides. Filled or reinforced grades may to control sinks, voids, molded-in
Naturally balanced runner systems have require hardened components and stresses, and/or warpage in the finished
total symmetry in the length and diam- inserts. part.
eter of the runner elements and layout
geometry. This helps ensure that each The gate land length should be as short
cavity of multi-cavity molds receive as possible and never longer than 0.060
polymer flow at the same temperature in. (1.5 mm). To reduce jetting, position
and pressure, promoting consistent part the gate so that the melt flow impinges
quality. on an opposite wall or a core pin at a

Figure 32 Figure 33
Runner Design Gate Designs Which Prevent Jetting

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38 of 65
 TOOLING, continued

distance of within three times the gate cavity will reduce gate blush. A wide Sprue Gates
diameter (see Figure 33). Gates for flare will help the material to enter
glass-fiber-reinforced grades of smoothly and reduce chances for surface Sprue gates are simple but tend to pro-
Durethan resin should be about 25% blemishes at the gates. mote splay in parts having heavy walls.
larger than for standard grades. The diameter of the sprue base is usual-
ly controlled by the required sprue
Pinpoint Gates length, so keep the sprue as short as
Edge Gates possible.
The diameter of pinpoint gates varies
Examples of edge gate dimensions are from 0.040 to 0.100 in. (1.0 to 2.5 mm), A minimum radius of 0.015 in.
shown in Figure 34. The gate thickness depending on part thickness and weight. (0.4 mm) at the sprue/cavity edge is
(depth) can vary from 45% to 65% of Place the gate on a small conical tab recommended. Sprues which are too
the nominal part thickness. The gate with a cone angle of 60°– 90° to im- large can cause lengthy cycle times.
width is usually 2 or 3 times the gate prove impact strength and reduce the
thickness. Even wider gates are used to possibility of gate blush. Keep land
reduce shear in large-volume parts. A length as short as possible. A typical
rounded edge where the gate meets the pinpoint gate is shown in Figure 35.

Figure 34 Common Edge Gate Figure 35 Typical Pinpoint Gate

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39 of 65
Tunnel Gates INSERT MOLDING MOLDED-IN STRESS

Tunnel gates are variations of the pin- Molded-in inserts have been used with Take all reasonable care to minimize
point gate. Maintain a sharp edge on the Durethan resin with good results. Be- stress within the part during the mold-
gate steel in order to properly shear off fore using a molded-in insert, consider ing operation. This is critical to help
the gate without tearing it from the part. the balance between tool design, insert ensure that the molded part meets its
Hardened gate inserts are recommended loading methods (manual or robotic), required level of end-use performance
for filled or reinforced grades. and part end-use requirements. and that the material can provide its
expected level of property performance.
When using molded-in inserts, heat Use suggested processing temperatures,
Ring (or Diaphragm) Gates them to at least the same temperature machine conditions, adequate gating,
as the mold before placing them in the and part and tool design to avoid any
Ring gates work well with cylindrical tool. This will minimize any stress that unnecessary molded-in stress.
parts because weld lines can be avoided may be caused by wide temperature
in most cases. A variation of this type of differentials.
gate is often used for parts such as filter
bowls.

Figure 36 Tunnel-Gate Configuration Figure 37 Diaphragm Gate

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40 of 65
 TROUBLESHOOTING GUIDE

BURN MARKS

Description of Problem Probable Causes Possible Corrective Action

Localized burning and degradation of ● Gate / runner size / shape. ● Enlarge flow areas.
the polymer can occur when entrapped ● Radius sharp corners.
air rapidly compressed by the injected
● Reduce injection speed.
melt elevates the tool surface tempera-
ture as it discharges from the vent.
● Barrel overheating. ● Check actual melt temperature.
● Check heater bands and controllers.
● Nozzle overheating. ● Check for blockage.
● Increase tip inside diameter to at least
80% of sprue bushing size.
● Check heater bands and controllers.

● Inadequate mold venting. ● Add or enlarge vents to a maximum depth

of 0.0010 in. (0.025 mm).
● Check vent channels for blockage.

Figure 38 Burn Marks

41 of 65
DIMENSION CONTROL

Description of Problem Probable Causes Possible Corrective Action

The inability of a plastic part to retain ● Incorrect processing conditions. ● Check for uniform feed and cushion, cycle
the precise shape in which it was to cycle.
molded is often caused by improper ● Fill mold as rapidly as possible.
processing conditions and incorrect ● Increase cooling time.
mold design. Orientation of glass fiber
● Increase mold temperature to the upper
and part geometry can also contribute portion of the recommended range for the
to the loss of dimensional control in resin being processed.
molded parts. ● Check the machine for erratic performance.

● Incorrect mold design. ● Balance cavities and runner system for

uniform flow.
● Increase gate size and / or relocate gate.
● Reduce the number of cavities in use.
● Check for uniform cooling with a surface
pyrometer.
● Check tool design for proper shrink factor.
● Check cooling system.
● Adjust the temperature of the mold halves
separately.

42 of 65
 TROUBLESHOOTING GUIDE, continued

DISCOLORATION

Description of Problem Probable Causes Possible Corrective Action

Surface discoloration appears mainly at ● Contamination. ● Purge the machine.

the weld line or at the end of a flow path. ● Check hopper and feed zone for
It is usually caused by air trapped in the contaminants.
mold and typically appears before burn
marks develop. ● Overheating. ● Lower material temperatures by:
✔ Lowering cylinder zone temperatures.
✔ Decreasing screw speed.
✔ Reducing back pressure.
● Lower nozzle temperature.
● Decrease injection speed.

● Inadequate venting. ● Check vents in mold.

● Clean vents.
● Provide additional venting.

● Long residence time. ● Check screw for excessive clearance.

● Move mold to smaller shot-size press.
● Reduce overall cycle time.

Figure 39 Discoloration

43 of 65
FLASH

Description of Problem Probable Causes Possible Corrective Action

Flash is a thin, surplus web of plastic ● High melt temperature. ● Lower material temperatures by:
material attached to the molded part ✔ Lowering cylinder zone temperatures.
along the parting line. Flash formation
✔ Decreasing screw speed.
depends on the fit of the mold at the
✔ Reducing back pressure.
parting line, the applied clamping force,
and the viscosity of the resin melt.
● Incorrect processing. ● Lower injection pressure.
● Reduce overall cycle time.
● Decrease injection speed.

● Mold setup. ● Check mold closure and lockup.

● Check platen alignment.

● Excessive vent depth. ● Check that the vent depth is at a maximum

depth of 0.0010 in. (0.025 mm).

● Insufficient clamp pressure. ● Move mold to a larger tonnage machine.

● Wet material. ● Check drying procedure.

● Measure moisture content of pellets in the
hopper.

Flash
Figure 40

44 of 65
 TROUBLESHOOTING GUIDE, continued

NOZZLE DROOL

Description of Problem Probable Causes Possible Corrective Action

Drool is usually caused by an increase ● High melt temperature. ● Lower nozzle temperature.
in pressure on the melt from steam in ● Lower material temperatures by:
the injection molding machine barrel ✔ Lowering cylinder zone temperatures.
generated by moisture in the resin.
✔ Decreasing screw speed.
✔ Reducing back pressure.

● Incorrect processing conditions. ● Lower pressure in machine cylinder.

● Reduce injection forward time.
● Increase decompress time.
● Reduce overall cycle time.

● Wet material. ● Check drying procedure.

● Measure moisture content of pellets in
the hopper.

● Incorrect nozzle. ● Change to smaller-orifice nozzle.

● Use reverse-taper nozzle.
● Use decompression.

Nozzle Drool
Figure 41

45 of 65
NOZZLE FREEZE-OFF

Description of Problem Probable Causes Possible Corrective Action

Due to the rapid crystallization of poly- ● Excessive heat loss at nozzle. ● Raise nozzle temperature.
amide resins, material in the nozzle can ● Raise mold temperature.
freeze off if the nozzle internal diameter ● Insulate nozzle from sprue bushing.
is too small, the mold temperature is too
● Decrease cycle time.
low, or a nozzle heater band is defective.
● Change to lower-orifice nozzle.

● Low melt temperature. ● Raise material temperature by:

✔ Raising zone temperatures—first the
zone, then the nozzle.
✔ Increasing screw speed.

Figure 42 Nozzle Freeze-Off

46 of 65
 TROUBLESHOOTING GUIDE, continued

SHORT SHOTS / COLD FLOW

Description of Problem Probable Causes Possible Corrective Action

Short shots are typically used in the ● Incorrect processing conditions. ● Increase injection speed.
start-up procedure of any tool to deter- ● Increase injection pressure.
mine the correct process parameters ● Increase injection time.
for the part. When this is done, make
sure that the initial shot weight, con-
● Insufficient venting. ● Check vents in mold.
tacts the ejector pins to facilitate part
release. ● Clean vents.
● Provide additional venting.
● Check for worn non-return valve or
check ring.

● Low melt temperature. ● Raise material temperature by:

✔ Raising cylinder zone temperatures.
✔ Increasing screw speed.
● Raise mold temperature.

● Insufficient resin feed. ● Increase size of nozzle, sprue, gate

and/or runner system.
● Check for an obstruction in the hopper
throat.
● Increase shot size.

Figure 43 Short Shots

47 of 65
SINKS / VOIDS

Description of Problem Probable Causes Possible Corrective Action

Sinks and / or voids can result when ● Insufficient resin feed. ● Increase shot size and / or decrease
insufficient material is injected into the cushion.
cavity and often occurs in the thickest
● Incorrect processing conditions. ● Increase injection pressure.
sections of the part. Voids occur when
the part’s external surfaces solidify ● Increase hold pressure and / or injection
more rapidly and shrinkage continues time.
internally. Sinks are associated with ● Increase injection speed.
high mold temperatures; voids are
associated with colder mold ● Insufficient flow. ● Increase size of nozzle, sprue, gate,
temperatures. and/or runner system.
● Move gates closer to thick sections.

● Incorrect temperatures. ● Lower mold temperature in the presence

of sinks.
● Raise mold temperature in the presence
of voids.
● Reduce melt temperature.

● Wet material. ● Check for proper drying.

Sinks / Voids
Figure 44

48 of 65
 TROUBLESHOOTING GUIDE, continued

STICKING: CAVITY / SPRUE

Description of Problem Probable Causes Possible Corrective Action

Parts and / or sprues that do not eject ● Mold overpacking. ● Decrease injection pressure.
freely will prevent molding machines ● Decrease injection speed.
from cycling automatically. Insufficient ● Decrease booster time.
part draft and / or a mismatched sprue
● Adjust feed for constant cushion.
bushing and nozzle are typical causes.
● Decrease melt temperature.

● Material not set up in the mold. ● Increase cooling time.

● Lower mold temperature.

● Incorrect mold design. ● Check mold for insufficient draft and / or

undercuts.
● Draw polish the cores.

● Sprue hang-up. ● Check sprue bushing fit with nozzle.

● Increase nozzle temperature.

Figure 45 Sticking: Cavity / Sprue

49 of 65
POOR SURFACE FINISH / LACK OF GLOSS

Description of Problem Probable Causes Possible Corrective Action

A poor or dull surface finish is a typical ● Incomplete crystallization. ● Raise mold temperature.
sign that the part is not fully crystallized
and the mold temperature must be ● Mold underpacking. ● Increase feed and / or injection pressure.
increased. Underpacked parts will ● Increase injection speed.
exhibit a surface blemish at weld lines ● Raise material temperature by:
and in the area which fills last.
✔ Raising cylinder zone temperatures.
✔ Increasing screw speed.

Poor Surface Finish /

Figure 46 Lack of Gloss

50 of 65
 TROUBLESHOOTING GUIDE, continued

WARPAGE / PART DISTORTION

Description of Problem Probable Causes Possible Corrective Action

Sections of a molded part cool at ● Unequal mold-half cooling. ● Check for uniform mold temperatures.
different rates from the ejected melt
temperature to room temperature due ● ●
Distortion upon ejection. Check for uniform part ejection.
to variations in part geometry and wall
● Reduce drop-height for part.
thickness. Differential shrinkage occurs
and the part tends to become concave
● Glass fiber alignment. ● Decrease injection speed.
on the side that cooled last. Glass fiber
reinforcement can contribute to warpage ● Increase injection pressure.
because the fibers tend to orient in the ● Move gates to improve fiber orientation.
direction of flow and thus create less
shrinkage in the flow direction than in ● Material not set up completely prior to ● Increase cooling time.
the cross-flow direction. ejection. ● Lower material temperature.

Figure 47 Warpage

51 of 65
WELD LINES

Description of Problem Probable Causes Possible Corrective Action

Weld lines occur where two melt streams ● Incomplete remixing of melt streams ● Increase injection pressure.
join and the leading surfaces of the con- within the part. ● Increase injection speed.
tacting melt streams are colder than the ● Increase injection time.
body of the melt and do not become fully
● Raise mold temperature.
fused. When the melt streams do not
● Raise material temperature.
fuse well, the result is weakness at the
weld line. Weld line strength depends
● Insufficient injection pressure. ● Vent the cavity in the weld area.
primarily on the material temperature at
the weld junction and secondarily on ● Provide an overflow adjacent to weld area.
injection and holding pressure.
● Insufficient injection speed. ● Change gate location to alter flow pattern.
● Increase gate and runner system size.

Weld Lines
Figure 48

52 of 65
 SAFETY CONSIDERATIONS

GENERAL HEALTH AND SAFETY

INFORMATION
Good molding practice calls for opera-
tors to wear safety glasses and / or face Appropriate literature has been assem-
shields, especially during purging, and bled which provides information con-
use proper gloves and other appropriate cerning health and safety precautions that
garments when handling hot tools and must be observed when handling LANXESS
auxiliary equipment. Material safety Corporation products mentioned in this
data sheets (MSDS) are available and publication. Before working with any of
should be consulted prior to processing these products, you must read and
Durethan polyamide resins. become familiar with the available
information on their hazards, proper
use, and handling. This cannot be over-
emphasized. Information is available in
several forms, e.g., material safety data
sheets and product labels. Consult your
LANXESS Corporation representative or
contact the Product Safety and Regula-
tory Affairs Department in Pittsburgh,
Pennsylvania at 800-LANXESS.

For materials mentioned that are not

LANXESS Corporation products, appropri-
ate industrial hygiene and other safety
precautions recommended by their
manufacturer(s) should be followed.

53 of 65
 GENERAL INFORMATION

DEVELOPMENTAL PRODUCT TECHNICAL SUPPORT Upon request, LANXESS Corporation will

INFORMATION furnish such technical advice or
To get material selection and /or assistance it deems to be appropriate
Any product in this publication with a design assistance, just write or call and in reference to your use of our product,
grade designation containing the letters let us know who you are and what your Durethan polyamide resin. It is ex-
DP, KU, or KL is classified as a devel- needs are. So that we can respond pressly understood and agreed that,
opmental product. Testing of properties efficiently to your inquiry, here are since all such technical advice or assis-
and application suitability is not final. some of the points of information we tance is rendered without compensation
Further information, including data would like to know: physical descrip- and is based upon information believed
which could change or add hazards tion of your part(s) and engineering to be reliable, the customer assumes
associated with use, may be developed. drawings, if possible; current material and hereby expressly releases LANXESS
Such information might be needed to being used; service requirements, such Corporation from all liability and
properly evaluate and /or use this prod- as mechanical stress and/ or strain, obligation for any advice or assistance
uct. Use is undertaken at the sole risk peak and continual service tempera- given or results obtained. Moreover, it
of the purchaser. Such material is sold ture, types of chemicals to which the is your responsibility to conduct end-
“as is” without warranty or guarantee. part(s) may be exposed, stiffness use testing and to otherwise determine
Commercialization and continued required to support the part itself or to your own satisfaction whether or not
supply are not assured. LANXESS another item, impact resistance, and LANXESS Corporation products and infor-
Corporation reserves the right to assembly techniques; applicable mation are suitable for your intended
discontinue at any time. government or regulatory agency test uses and applications.
standards; tolerances that must be held
in the functioning environment of the For assistance, contact any of our
REGULATORY COMPLIANCE regional sales offices listed on the back
part(s); and any other restrictive factors
or pertinent information of which we cover or call or write us at the follow-
Some of the end uses of the products should be aware. ing address:
described in this publication must
comply with applicable regulations, In addition, we can provide processing LANXESS Corporation
such as those of the FDA, USDA, NSF, assistance nationwide through a net- Durethan Product Management
and CPSC. If you have questions on work of regional Field Technical 111 RIDC Park West Drive
the regulatory status of these products, Service Representatives. We can help Pittsburgh, PA 15275-1112
contact your LANXESS Corporation customers optimize the quality and per- Phone: 800-LANXESS
representative or the Regulatory Affairs formance of their parts by offering the
Manager in Pittsburgh, Pennsylvania. following types of assistance: on-site
processing, equipment and productivity
audits, startup and troubleshooting
support, and tool design.

54 of 65
 APPENDIX A:
LIST OF TABLES

Page No. Description Table No. Page No. Description Table No.

5 Grade Composition and Designations Table 1 21 Injection Pressure for Durethan Resin Table 7a
for Durethan Resins

21 Hold Pressure for Durethan Resin Table 7b

6 Performance Additives and Designations Table 2
for Durethan Resins
22 Injection Speed for Durethan Resin Table 7c

6 Color Coding System for Durethan Table 3

Polyamide Resin 22 Injection Cushion for Durethan Resin Table 7d

14 Suggested Starting Conditions for Table 4 23 Back Pressure for Durethan Resin Table 7e
Processing Durethan Resins

23 Screw Speed for Durethan Resin Table 7f

17 Dehumidifying Hopper Dryer Table 5
Troubleshooting Guide
24 Clamp Tonnage for Durethan Resin Table 7g

19 Barrel Heating Temperatures for Table 6a

Durethan Resin 24 Mold Temperature for Durethan Resin Table 8

19 Nozzle Temperatures for Table 6b 34 Suggested Starting Conditions for Table 9

Durethan Resin Processing Durethan Resins

20 Melt Temperatures for Durethan Resin Table 6c

55 of 65
 APPENDIX B:
LIST OF FIGURES

Page No. Description Figure No. Page No. Description Figure No.

7 Durethan Polyamide Resin Pellets Figure 1 18 Temperature Zones / Figure 14

Machine Cross Section

7 Label Information for Durethan Figure 2

Polyamide Resin 20 Making an Accurate Melt Figure 15
Temperature Reading

8 Typical Injection Molding Machine Figure 3

25 Measuring Mold Surface Temperature Figure 16
During the Injection Molding Cycle
8 Typical Injection Molding Screw Figure 4

25 Variation in the Temperature of the Figure 17

9 Screw Profile Figure 5 Mold Surface During the Injection
Molding Cycle

9 Preferred Screw Flight Depths Figure 6

26 Effect of Part Wall Thickness on Figure 18
Total Mold Cycle Time at Various
10 Free-Flowing Sliding Check-Ring- Figure 7 Mold and Melt Temperatures
Style Non-Return Valve

27 Effect of Process Conditions on Figure 19

10 Flow Characteristics of the Figure 8 Shrinkage with Non-Reinforced
Non-Returning Ring Valve Grades of Durethan Resin

11 Removable and Non-Removable Figure 9 28 Regrind Material Figure 20

Nozzle Tips

29 Moisture Absorption Rate of Parts Figure 21

11 Sliding Shut-Off Nozzle Figure 10 Molded of Durethan B Resin, Exposed
to a “Tropical Environment” of
95% – 98% RH at 105°F (40°C)
12 Needle Shut-Off Nozzles (Closed) Figure 11

29 Water Absorption by Non-Reinforced Figure 22

15 Typical Desiccant Dehumidifying Figure 12 Durethan B Resin Immersed in Water
Hopper Dryer System at 140°F (60°C) as a Function of
Wall Thickness and Time
16 Desiccant Dehumidifying Hopper Figure 13
Dryer System Airflow

56 of 65
 APPENDIX B:
LIST OF FIGURES

Page No. Description Figure No. Page No. Description Figure No.

30 Water Absorption by Non-Reinforced Figure 23 39 Typical Pinpoint Gate Figure 35

Durethan B Resin When Stored in a
Standard Atmosphere of DIN 50014
as a Function of Wall Thickness 40 Tunnel-Gate Configuration Figure 36
and Time

40 Diaphragm Gate Figure 37

30 Equilibrium Moisture Content of Figure 24
Durethan B Resin as a Function of
Relative Humidity, Measured at 41 Burn Marks Figure 38
Room Temperature

43 Discoloration Figure 39
31 Linear Change in Length of Rectangular Figure 25
Bars Injection Molded in Various Grades
of Durethan B Resin as a Function of 44 Flash Figure 40
Water Content
45 Nozzle Drool Figure 41
32 Mechanical Cleaning of the Screw Figure 26
46 Nozzle Freeze-Off Figure 42
35 Vent Depth Figure 27
47 Short Shots Figure 43
35 Vent Placement Figure 28
48 Sinks / Voids Figure 44
36 Draft Figure 29
49 Sticking: Cavity / Sprue Figure 45
36 Sprue Design Figure 30
50 Poor Surface Finish / Lack of Gloss Figure 46
37 Sprue Pullers Figure 31
51 Warpage Figure 47
38 Runner Design Figure 32
52 Weld Lines Figure 48
38 Gate Designs Which Prevent Jetting Figure 33

39 Common Edge Gate Figure 34

57 of 65
 INDEX

A Mechanical Cleaning of the Screw D

abrasion resistance, 5 (Figure 26), 32 degradation, melt, 12
additives, 6, 27 screw, 32 desiccant, contaminated or worn out, 17
air entrapment, 23, 43 cold flow, 47 desiccant dehumidifying hopper
application testing, 54 cold-slug wells, 37 dryer, 15-17
applications (see also markets and color, 6 design assistance, 54
applications), 5 Color Coding System for Durethan developmental product(s), 54
automotive applications, 5 Polyamide Resin (Table 3), 6 dew point, dryer inlet air, 16, 17
natural tints, 6 dew-point meter, 16, 17
B opaque, 6 diaphragm gates, 40
back pressure, 12, 23, 43, 44, 45 color concentrates, 28 Diaphragm Gate (Figure 37), 40
Back Pressure for Durethan Resin conditioning parts (see post- differential shrinkage, 51
(Table 7e), 23 mold conditioning) dimensional change, part, 31
barrel, 41, 45 consumer appliances applications, 5 dimensional control, 25, 42
capacity, 13 contaminated desiccant, 17 dimensional tolerances, 18
heaters, 8, 12 contaminated feedstock, 7, 43 dimensional uniformity, part, 13
heating temperature, 19 controls, process, 12, 13 discoloration, 10, 15, 16, 24, 43
Barrel Heating Temperatures for closed-loop systems, 13 Discoloration (Figure 39), 43
Durethan Resin (Table 6a), 19 cooling time, 13 Draft (Figure 29), 36
liner, 9 dimensional uniformity, 13 drool, 11, 20, 38, 45
residence time, 13, 22 hold pressure, 13 dryer, resin, 15, 16, 17
temperature, 13 injection stroke, 13 air heating elements, 17
temperature sensors, 12, 13 melt pressure, 13 airflow, 16
temperature set point, 13 part weight, 13 Dehumidifying Hopper Dryer
blow molding, 5 switchover point, 13 Troubleshooting Guide (Table 5), 17
bubbles, 23, 41, 43 controls and melt uniformity, 13 desiccant dehumidifying hopper dryer, 15
burn marks, 41 cooling time, 18, 24, 27, 42, 50, 51 Desiccant Dehumidifying Hopper Dryer
Burn Marks (Figure 38), 41 cross-flow shrinkage, 36, 51 System Airflow (Figure 13), 16
crystalline-to-amorphous ratio, 24 dew point of inlet air, 16
C crystallinity, 25 dirty or clogged filter(s), 17
checking melt temperature, 20 cycle length/cycle time, 12, 19, 24, 27, 39, hopper capacity, 15
chemical resistance, 5, 25 43, 44, 45, 46 incorrect process air temperature, 17
clamp tonnage, 24 cylinder, injection molding machine (see insufficient inlet airflow, 17
Clamp Tonnage for Durethan Resin also barrel), 32 poor dew point, 17
(Table 7g), 24 cylindrical parts, 40 temperature control, 17
clamping force, 44 Typical Desiccant Dehumidifying
cleaning, Hopper Dryer System (Figure 12), 15
injection molding machine, 32

58 of 65
 INDEX, continued

drying, 15, 48 engineering thermoplastic, 5 flow length, 19

drying conditions, 16 entrapped air, 23, 41, 43 flow orientation, 36
airflow, 16 equilibrium moisture content, 31 flow path, 43
dew point of inlet air, 16 ambient temperature, 31 food film packaging applications, 5
inlet air temperature to hopper, 16 Equilibrium Moisture Content of frictional heating, 18, 19
material residence time, 17 Durethan B Resin as a Function of front zone temperature, 19
Durethan A resins, 6 relative Humidity Measured at Room fumes, 13
Durethan B resins, 6 Temperature (Figure 24), 30 furniture applications, 5
Durethan resins relative humidity, 31
drying, 7, 15, 48 wall thickness, 31 G
Durethan Polyamide Resin Pellets equipment and productivity audits, 54 gates /gating, 38, 39, 40, 42, 52
(Figure 1), 7 external heaters, 12, 18 edge gates, 39
handling, 15 extrusion, 5 gate blush, 39
labeling, 7 film, 5 Gate Designs Which Prevent Jetting
packaging, 7 profile, 5 (Figure 33), 38
plasticizing efficiency, 9 gate inserts, 40
specific heat, 9 F gate land, 38
dynamic fatigue resistance, 5 face shields, 53 gate location, 38
dynamic load capacity, 5 fatigue resistance, 5 gate type, 38
feedstock, 7 jetting, 38
E contamination, 7 melt flow, 38
edge gates, 39 handling, 15 molded-in stress, 38
Common Edge Gate (Figure 34), 39 moisture, 7 part design, 38
large-volume parts, 39 filled resin grades, 23, 27 pinpoint gates, 39
shear, 39 back pressure, 23 reinforced resin grades, 39
surface blemishes, 39 fiberglass breakage, 23 ring or diaphragm gates, 40
ejection, part, 13 part shrinkage, 27 sinks, 38
ejector pins, 47 filler, amount in reinforced grades, 6 sprue gates, 39
electrical/electronic applications, 5 film extrusion, 5 tunnel gates, 40
electrical insulating properties, 5 flash, 21, 24, 44 voids, 38
electronic wiring device and switch Flash (Figure 40), 44 gate inserts, 40
applications, 5 flow characteristics, 10 general-purpose resin grades, 5
elongation and part moisture Flow Characteristics of the Non- glass-fiber-reinforced, 5
absorption, 29 Returning Ring Valve (Figure 8), 10 unreinforced, 5
end-use testing, 54 flow direction, 51
flow fronts, 36

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glass-fiber-reinforced parts, 36 I injection speed, 18, 22, 27, 33, 41, 43, 49,
glass-fiber-reinforced resin/resin impact resistance and part moisture 50, 51, 52
grades, 5, 6, 9, 10, 27, 31, absorption, 29 Injection Speed for Durethan Resin
38, 39, 40, 51 impact strength, 5, 39 (Table 7c), 22
barrel heating temperature, 19 impact-modified resin grades, 5 injection stroke, 13
breakage of glass fibers, 12, 23 glass-fiber-reinforced, 5 injection time, 47, 52
gloves, 53 mineral-filled, 5 inlet airflow, resin dryer, 17
grade composition, 6 unreinforced, 5 insert molding, 40
Grade Composition and Designation for industrial/mechanical applications, 5 internal stresses, 25
Durethan Resins (Table 1), 5 industrial goods packaging film
grade designation, 6 applications, 5 J
amount of filler in reinforced injection cushion, 22 jetting, 22, 38
grades, 6 Injection Cushion for Durethan Resin
grade composition, 6 (Table 7d), 22 L
grade number, 6 injection molding machine, 8, 9, 12, 13, label, 7
prefix, 6 15, 18, 32 Label Information for Durethan
suffix, 6 automatic operation, 12 Polyamide Resin (Figure 2), 7
viscosity of unfilled resin grades, 6 barrel heaters, 8, 12 land length, 39
barrel liner, 9 large-volume parts, 39
H barrel temperature sensors, 12, 13 lawn and garden equipment applications, 5
handling Durethan resins, 15 external heaters, 12 Linear Change in Length of Rectangular
health and safety, 53 initial processing settings, 18 Bars Injection Molded in Various
heat resistance, 5 mechanical cleaning, 32 Grades of Durethan B Resin as a
heat zones, 33 operating conditions, 13 Function of Water Content
heat-up time, 33 preparation, 32 (Figure 25), 31
heater bands and controllers, 41 process controls, 12, 13 load capacity, 5
heating the melt, 12 purging and cleaning, 32
heavy-walled parts, 39 screw, 8, 9, 10, 12, 13, 32, 43 M
hold pressure, 13, 18, 21, 27, 48, 52 shot size and machine capacity, 13 machine capacity, 13
Hold Pressure for Durethan temperature control, 12 machine conditions, 40
Resin (Table 7b), 21 time and pressure control, 13 markets and applications, 5
hold time, 18, 27 Typical Injection Molding Machine automotive, 5
hopper capacity, dryer, 15 Figure 3), 8 consumer appliances, 5
hot runner molds, 38 vented barrel, 15 electrical/electronic, 5
hot tools, 53 ventilation, 13 furniture, 5
injection pressure, 18, 21, 33, 47, 50, 51, 52 industrial goods, 5
Injection Pressure for Durethan Resin
(Table 7a), 21

60 of 65
 INDEX, continued

industrial /mechanical components, 5 moisture content of parts, 29 texturing, 36

lawn and garden equipment, 5 equilibrium, 31 tolerances, 36
packaging film, 5 Moisture Absorption Rate of Parts undercuts, 36
power tools, 5 Molded of Durethan B Resin Exposed venting, 35
material degradation, 8, 10, 13, 22, 23 to a “Tropical Environment” of warpage, 28
material flow, 11 95%- 98% RH at 105°F (40°C) weld lines, 36
material residence time in barrel, 13, 22 (Figure 21), 29 mold filling, 20
in resin dryer, 17 properties, 29 mold filling analysis, 28
material safety data sheets (MSDS), 53 rigidity, 29 mold fit at parting line, 44
material selection assistance, 54 strength, 29 mold gates, size and location, 8
Mechanical Cleaning of the Screw Water Absorption by Non-Reinforced mold geometry, 20
(Figure 26), 32 Durethan B Resin Immersed in Water mold lifters and cams, 26
medical packaging film applications, 5 at 140°F (60°C) as a Function of Wall mold lubrication and electronic
melt contamination, 9 Thickness and Time (Figure 22), 29 applications, 27
melt degradation, 12, 24 Water Absorption by Non-Reinforced mold over-packing, 49
melt flow, 12, 38 Durethan B Resin When Stored in a mold release agents, mold lubrication, 27
melt phase, 19 Standard Atmosphere of DIN 50014 mold temperature, 18, 24, 25, 26, 27, 33,
melt pressure, 13 as a Function of Wall Thickness and 42, 46, 47, 48, 49, 50, 52
melt temperature, 12, 13, 19, 20, 27, 33, 41, Time (Figure 23), 30 Measuring Mold Surface Temperature
43, 44, 45, 46, 47, 48, 49, 50, 51 moisture removal, resin, 15 During the Injection Molding Cycle
Making an Accurate Melt Temperature mold cavity, 37 (Figure 16), 25
Reading (Figure 15), 20 mold construction, 36 Mold Temperature for Durethan Resin
melt Temperature for Durethan Resin mold coolant, 26 (Table 8), 24
(Table 6c), 20 mold cooling system, 42 mold temperature control, 25, 26
melt uniformity, 23 mold cycle, 12, 27 bubblers and heat pipes, 26
mineral-filled resin/resin grades, 5, 9 Effect of Part Wall Thickness on control zones, 26
moisture contamination, 7, 15 Total Mold Cycle Time at Various electrical resistance heaters (cartridge
moisture content of resin, 7, 16, 44, 45 Mold and Melt Temperatures heaters), 25
Equilibrium Moisture Content of (Figure 18), 26 heat transfer fluid, 25
Durethan B Resin as a Function of mold design, 28, 35, 36, 42, 49 mold coolant, 26
Relative Humidity Measured at Room cross-flow shrinkage, 36 temperature fluctuations, 26
Temperature (Figure 24), 30 flow orientation, 36 Variation in the Temperature of the Mold
moisture content of resin and property material selection, 35 Surface During the Injection Molding
performance, 16 mold filling analysis, 28 Cycle (Figure 17), 25
moisture content of resin, acceptable part draft, 36 mold textures, 21
level, 16 surface finish, 35

61 of 65
mold types, 36, 38 Nozzle Drool (Figure 41), 45 moisture absorption rate, 29
hot runner, 38 nozzle freeze-off, 46 release, 47
two- or three-plate molds, 36 Nozzle Freeze-Off (Figure 42), 46 removal, 26
single- and multi-cavity molds, 37 Nozzle Temperature for Durethan rigidity, 29
mold vents/venting, 41, 43, 47 Resin (Table 6b), 19 shrinkage, 27, 42
molded-in inserts, 40 nozzle temperature set point, 13 strength, 29
molded-in stress, 38, 40 nozzle tip freeze-off, 38 weight, 13
molding conditions, 24 nozzle tips, 11 Part and Mold Design-Thermoplastics, 5
mold temperature, 24 Removable and Non-Removable 28, 35
molding cycles, 13 Nozzle Tips (Figure 9), 11 performance additives, 6
monitoring moisture content of dryer Performance Additives and Designations
inlet air, 16 O for Durethan Resins (Table 2), 6
opaque colors, 6 physical properties, 7, 25
N orientation, 25 pinpoint gates, 39
natural tints, 6 orientation of glass fiber, 42 gate blush, 39
nomenclature, 6 output rates, 25 impact strength, 39
non-return valve, 47 over-packing, 21, 33, 49 land length, 39
nozzle, 8, 11, 12, 19, 32, 38, 41, 46, overheating the melt, 19 Typical Pinpoint Gate (Figure 35), 39
47, 48, 49 polyamide (nylon) type 66 engineering
backflow, 22 P polymers, 6
discharge opening, 11 packaging film, 5 polyamide type 6 resins, 6
drool, 11 packaging, Durethan resins, 7 post-mold conditioning, 29, 30, 31
freeze-off, 38, 46 packing the mold, 21, 22 Durethan Polyamide–Environmental
heater and controller system, 11, 19 part, 11, 13, 18, 21, 26, 27, 28, 29, Conditioning, 32
length, 11 31, 33, 36, 38, 42, 47, 49, 51 end-use requirements, 29
Needle Shut-Off Nozzles (Closed) appearance, 18 methods, 29
(Figure 11), 12 blemishes, 11 parameters, 30, 31
opening, 11 contamination, 33 prolonged exposure to hot water, 31
shut-off, 11 design, 38 reinforced, 30
size, 11 dimensional change, 31 unreinforced, 30
Sliding Shut-Off Nozzle dimensions, 18 Water Absorption by Non-Reinforced
(Figure 10), 11 distortion, 51 Durethan B Resin Immersed in Water
sticking, 12 draft, 36, 49 at 140°F (60°C) as a Function of Wall
suck-back, 11 Draft Angle, Length, and Taper Thickness and Time (Figure 22), 29
temperature/temperature Relationship (Figure 28), 35 Water Absorption by Non-Reinforced
control, 11, 13, 43, 45, 46, 49 ejection, 13, 21, 28 Durethan B Resin When Stored in a
throughput, 11 enlargement/dimensional change, 31 Standard Atmosphere of DIN 50014
tips, 11 geometry, 36, 42, 51 as a Function of Wall Thickness and
nozzle and sprue bushing, 11 Time (Figure 23), 30

62 of 65
 INDEX, continued

post-mold shrinkage, 25 property testing, 54 reverse-taper nozzle, 45

power tool applications, 5 purging and cleaning the injection ring gates, 40
Preferred Screw Flight Depths molder, 32, 53 runners/runner systems, 37, 38, 42, 48, 52
(Figure 6), 9 purging material/compound, 32 balance, 38
preparation of injection molding cross sections, 38
machine, 32 R pressure drops, 38
process air temperature, 17 rapid cooling, 25 Runner Design (Figure 32), 38
process controls, 12 reciprocating screw machines, 8
processibility of Durethan resin, 5 regrind, 28 S
processing assistance, 54 Regrind Material (Figure 20), 28 safety/safety precautions, 53
processing conditions, 13, 42, 45 regulating melt temperature, 13 material safety data sheets (MSDS), 53
Effect of Process Conditions on regulatory compliance, 54 safety glasses, 53
Shrinkage with Non-Reinforced reinforced resin grades, 6, 9, 10, 27, 31, scrap, 36
Grades of Durethan Resin 38, 39, 40, 51 screw, 8, 9, 10, 12, 13, 32, 43
(Figure 19), 27 relative humidity and part moisture diameter, 9
processing inconsistencies, 12 absorption, 29 feed section, 9
processing parameters, 18, 19, 20, 21, 22, residence time, 12, 13, 26, 43 finish, 9
23, 24, 25, 27, 47 residual material, 32 flight lands, 9
back pressure, 23 resin, 5, 7, 9, 15, 16, 43, 44, 45, 48 flight-to-depth ratio, 9
barrel heating temperature, 19 contamination, 43 geometry, 8
clamp tonnage, 24 discoloration, 15 heating the melt, 12
dimensional tolerances, 18 drying, 7, 15, 16, 48 increasing-core-diameter (progressive-
hold pressure, 21 drying procedure, 44 core), 9
injection cushion, 22 handling, 15 large-diameter, 10
injection pressure, 21 labeling and packaging, 7 material, 9
injection speed, 22 melt and homogeneity, 9 Mechanical Cleaning of the Screw
melt temperature, 20 moisture, 7, 44, 45 (Figure 26), 32
mold temperature, 24, 25 storage and handling, 7 metering section, 9
nozzle temperature, 19 resin grades, 5 metering and feed zone depths, 8
part appearance, 18 general-purpose glass-fiber-reinforced, 5 pitch, 9
screw speed, 23 general-purpose unreinforced, 5 plasticizing efficiency, 9
processing temperature(s), 13, 40 impact-modified glass-fiber-reinforced, 5 Preferred Screw Flight Depths
production volume, 36 impact-modified unreinforced, 5 (Figure 6), 9
profile extrusion, 5 mineral-filled, 5 retraction, 12
properties, 5 Screw Profile (Figure 5), 9

63 of 65
 Screw Speed for Durethan Resin Durethan C copolymer, 6 T
(Table 7f), 23 Durethan T transparent resin, 6 technical support, 54
shear gap length, 10 specific heat, 9 design assistance, 54
short-transition-zone, 9 specks, 11 equipment and productivity audits, 54
slippage, 22 splay, 39 material selection assistance, 54
small-diameter, 10 spray, 22 processing assistance, 54
speed, 23, 43, 45, 46, 47, 50 sprue, 37, 38, 47, 48 start-up and troubleshooting support, 54
Typical Injection Molding Screw sprue bushing, 11, 37, 46, 49 temperature, nozzle, 11
(Figure 4), 8 Sprue Design (Figure 30), 36 temperature and part moisture
screw machines, reciprocating, 8 sprue gates, 39 absorption, 29
screw, three-zone general-purpose, 8 sprue length, 39 temperature control, 11, 12, 17
sensors, temperature, 12, 13 sprue pullers, 37 injection molder, 12
set points, temperature, 13 Sprue Pullers (Figure 31), 37 nozzle, 11
shear, 10, 39 start-up and troubleshooting support, 54 resin dryer, 17
shear gap, 10 start-up conditions/procedure, 18, 33, 47 temperature gradient, 12, 13
shear heating, 24 Suggested Starting Conditions for cylinder wall, 13
short screw, 8 Processing Durethan Resins melt, 12
short shots, 33, 47 (Table 4), 14 temperature profile, barrel heating, 19
Short Shots (Figure 43), 47 Suggested Starting Conditions for temperature sensors, 12, 13
shot size, 43, 47 Processing Durethan Resins Temperature Zones /Machine Cross Section
and machine capacity, 13 (Table 9), 34 (Figure 14), 18
and residence time, 13 sticking cavity, 49 texture, mold surface, 36
shot weight, 33, 47 sticking parts, 27 thermal damage, 23
Effect of Process Conditions on sticking sprue, 49 thermal stability, 5
Shrinkage with Non-Reinforced Sticking: Cavity/Sprue (Figure 45), 49 thin-walled parts, 20
Grades of Durethan Resin strength, 5 time and pressure control, 13
(Figure 19), 27 stress, 40 tints, 6
shrinkage, 27, 48, 51 suck-back, 11 tool design, 40, 42
shutdown procedure, 33 surface blemish(es), 39, 50 tool design assistance, 54
long-term, 33 surface finish, 15, 21, 22, 25, 28, 50 tool surfaces, 35
short-term, 33 Poor Surface Finish/Lack of Gloss tooling, 35
sinks, 21, 38, 48 (Figure 46), 50 transition sprue, 37
Sinks/Voids (Figure 44), 48 surface texture, 36 tunnel gates, 40
solidification of the melt, 22 switchover point, 13 Tunnel-Gate Configuration
specialty grades of resin, 6 (Figure 36), 40

64 of 65
 INDEX, continued

U W
undercut(s), 11, 36, 37, 49 wall thickness, 29, 30, 51
unfilled resin grades, 6 Effect of Part Wall Thickness on
uniform flow, 42 Total Mold Cycle Time at Various
uniform shots, 13 Mold and Melt Temperatures
unreinforced resin grades, 5, 31 Figure 18), 26
wall thickness and part moisture
V absorption, 29
valves, 10 warming resin pellets before processing, 15
ball-check, 10 warpage, 28, 38, 51
flow characteristics, 10 Warpage (Figure 47), 51
Flow Characteristics of the Non- Water Absorption by Non-Reinforced
Returning Ring Valve (Figure 8), 10 Durethan B Resin Immersed in Water
free-flowing, non-returning, sliding at 140°F (60°C) as a Function of Wall
check ring, 10 Thickness and Time (Figure 22), 29
Free-Flowing Sliding Check-Ring-Style Water Absorption by Non-Reinforced
Non-Return Valve (Figure 7), 10 Durethan B Resin When Stored in a
screw diameter, 10 Standard Atmosphere of DIN 50014 as
shearing gap, 10 a Function of Wall Thickness and
Vent Depth (Figure 27), 35 Time (Figure 23), 30
Vent Placement (Figure 28), 35 wear resistance, 5
vented molds, 35, 47 weld line(s), 22, 36, 43, 50, 52
vented-barrel injection molding weld line strength, 22, 52
machine, 15 Weld Lines (Figure 48), 52
ventilation, ventilating hood, 13 wiring device and switch applications, 5
viscosity, 6 worn-out desiccant, 17
voids, 21, 38, 48

65 of 65
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