Fire Retardant Polyester Resin Bruce Curry

October 1-3, 2003

Formulations
ABSTRACT fuel available to sustain combustion during fire by
The original fire retardant polyester resin formula- replacing part of the resin. Secondly, ATH contains
tions incorporated bromine and chlorine (halogens) 34.6% bound water that is released at high tempera-
into the polymer. The disadvantages to these for- tures [beginning at 230°C (446°F)] providing a
mulations were excessive toxic products and blanket effect, which limits the oxygen available for
smoke given off on exposure to a flame. Alumina tri combustion. Additionally, metal hydrates such as
-hydrate (ATH) has successfully been added to non- ATH absorb heat from the combustion zone, which
halogenated polyester resins to resolve the toxicity reduces the prospect of continued burning. Finally,
and smoke issues. ATH will produce a char during burning that results in
further flame retardant protection and less smoke
Unfortunately the high concentration of AHT detri- generation.
mentally affects the mechanical properties of com-
posites. Ammonium polyphosphate (APP) is an intu- Another fire retardant filler is ammonium polyphos-
mescent filler that is widely used in coatings for fire phate, which has been used for many years but not
resistance. Other papers have been presented that extensively in fiber reinforced composites. It is a fine-
describe the benefits of using filler blends of ATH grained non-toxic white powder that uses the intu-
and APP in composites. This paper describes the mescent effect for flame-retardancy in fire resistant
development of fire retardant formulations with coatings. It will foam on exposure to heat or flames.
emphasis on non-halogenated filled systems with The carbon foam layer protects the composite
varying amounts of ATH and APP. Neat and filled through its heat-insulating effect and reduces further
viscosities, cast resin mechanical properties are oxygen access. An APP supplier is suggesting that
reviewed. Also included in this paper are flamma- lower viscosities and improved fire resistance prop-
bility test results on composites tested according to erties can be achieved by decreasing the ATH con-
BSS 7239 toxicity test, ASTM E 84, ASTM E 162, tent and substituting part of the removed ATH will
ASTM E 662, and ASTM E 1354. APP. The focus of this paper is to confirm this sug-
gestion.
INTRODUCTION
Originally fire retardant polyester resins were made One significant disadvantage of using ATH as the
with halogenated raw materials such as tetra- only filler is that high loadings were required to meet
bromophthalic anhydride, tetrachlorophthalic an- specific fire retardant requirements such as ASTM E
hydydide or chlorendic acid or anhydride. These 84 class I ratings. Other disadvantages are that ATH
products performed well until toxicity issues be- does settle, reinforcements are harder to wet out
came important. In order to satisfy the needs for and finished parts were more brittle.
low toxicity products, non-halogenated general pur-
pose unsaturated polyester resins were introduced Five different test methods were used to evaluate
that were filled with products such as alumina tri- these new blends. ASTM E 84 “Surface Burning
hydrate (ATH). This filler was the key component in Characteristics of Building Materials” is a standard
meeting the fire retardant and toxicity require- test for general fire resistance and is widely recog-
ments. nized. Three tests that are often specified for mass
transit applications are ASTM E 162 “Surface Flam-
ATH products provide effective flame redundancy mability of Material Using a Radiant Heat Energy
by several routes. First, they dilute the amount of Source,” ASTM E 662 “Specific Optical Density of
Fire Retardant Polyester Resin Formulations, continued

Smoke Generated by Solid Materials” and Boeing Liquid resin properties both neat and filled, cast
Support Standard (BSS 7239) toxicity test. A test neat mechanical values, and the fire tests are pro-
that is being recognized increasingly as a more vided in tables. The resin made with 12.5% ammo-
reproducible fire retardant test is ASTM E 1354 nium polyphosphate and 47.5% ATH are coded AP-
“Heat and Visible Smoke Release Rates for Mate- P12.5/ATH 47.5. The resin made with 25% ammo-
rials and Products Using an Oxygen Consumption nium polyphosphate and 35% ATH are coded AP-
Calorimeter.” P25/ATH 35. The resin was promoted with 0.6%
cobalt 6%, 0.2% N, N-Dimethyl aniline (DMA) and
A summary of these tests follows: 1.5% methyl ethyl ketone peroxide (MEKP). Compo-
sites were made by wetting one layer of 450 grams
a) ASTM E 84- Laminates that are a minimum of per square meter (1.5 oz.) chopped strand mat.
45.7 cm (18 inches) wide by 7.3 meters (24 feet)
long are compared in burning characteristics to a The ASTM E 84 tunnel test (surface burning charac-
mineral fiber cement board, which is rated 0, and teristics of building materials) was run since it is
a red oak board that is rated 100. To meet an one of the most standard tests. The ASTM E 162
ASTM E 84 class I rating, the laminate in question (surface flammability of materials using a radiant
must have an ASTM E 84 rating of 25 or less. heat energy source), ASTM E 662 (specific optical
b) ASTM E 162- This test measures surface flam- density of smoke generated by solid materials) and
mability employing a radiant heat source rather the BSS 7239 toxic gas generation tests were run
than a flame. because they are often specified for mass transport
c) ASTM E 662- This test measures the optical applications. ASTM E 1354 (heat and visible
density of smoke using a radiant energy source. smoke release rates for materials and products us-
The smoke is measured in a flaming mode and a ing an oxygen consumption calorimeter) was run
non-flaming mode. In order to obtain the flaming because it is becoming more recognized as one of
mode, a row of equidistant flamelets is placed the most reproducible fire tests. It is also an excel-
across the lower edge of the specimen. lent screening test since a minimum amount of
d) BSS 7239- This test is a Boeing Support composite is required to run the test.
Standard that measures the amount of toxic gas-
es that are generated from a burning laminate in Liquid properties were tested with standard equip-
a controlled environment. ment and methods that are typically used in the
e) ASTM E 1354- 100 mm square coupons are industry. The casting preparation is found in Figure
burned while being subjected to an external heat a. Fire testing was run on composites only.
flux that is set from 0-100 kW/m2. Time to igni-
tion, heat release, smoke obscuration and mass RESULTS
loss are recorded. 1) Resin liquid properties of Firepel® K133-AAA-
00 with different ratios of ATH/APP fillers are found
This paper compares the fire/smoke properties of in Figure b.
three filled resin systems utilizing ATH and blends 2) The neat casting of Firepel® K133-AAA-00 was
of ATH/APP. tested for mechanical properties and those values
are in Figure c.
EXPERIMENTAL 3) Composite mechanical test results of neat res-
A non-halogenated general purpose unsaturated in versus 60% ATH filled laminate values are in Fig-
polyester resin Firepel® K133-AAA-00 containing ure d.
both styrene and methyl methacrylate (MMA) was 4) Fire Test Results (Firepel® K133-AAA-00 com-
chosen. In order to minimize the number of varia- posites with different ratios of ATH/APP fillers)
bles, three types of composites were prepared a) ASTM E 84 (surface burning characteristics of
keeping the total filler content constant. A stand- building materials) results are in Figure e.
ard formula that required a 40/60 ratio of res- b) ASTM E 162 (surface flammability of materials
in/ATH was chosen as a control. Ammonium poly- using a radiant heat energy source) results are in
phosphate replaced 12.5% and 25% of the ATH in Figure f.
two different composites. c) ASTM E 662 (specific optical density of smoke
generated by solid materials) results are in Figure g.
Fire Retardant Polyester Resin Formulations, continued

d) BSS 7239 (toxic gas generation) results are in 7) ASTM E 1354 data was difficult to analyze for
Figure h. conclusions. The APP12.5/ATH 47.5 composite
e) ASTM E 1354 (heat and visible smoke re- had the best result for the time to sustained igni-
lease rates for materials and products using an tion. The best average peak heat release was AP-
oxygen consumption calorimeter) is in Figure i. P25/ATH 35 and the best smoke rating was with
60% ATH.
DISCUSSION
1) The cast neat mechanical properties of a non- Generally the tests with APP were disappointing.
halogenated general purpose polyester resin are In discussions with our APP supplier, indications
typical of properties that are required in the FRP are that too much ATH was used, making it diffi-
industry. cult for the APP to exfoliate properly. High perfor-
2) A filled composite is more rigid as expected. mance flame-retardants like APP rely on the pres-
The strength values are lower due to not being ence of charable substrate (carbon based poly-
able to achieve as high of glass content. mer) to create an intumescent foam.
3) The 60% ATH and the APP25/ATH 35 met
ASTM E 84 class I flame spread and smoke CONCLUSION
spread rating but the APP12.5/ATH 47.5 did not; 1) With increasing concentration of APP, the vis-
however, ASTM E 84 is an inconsistent test. It is cosity increased which is a negative factor.
interesting to note that the smoke rating was 2) APP did not improve the fire and smoke prop-
higher with increasing amounts of APP. erties of a non-halogenated general purpose poly-
4) The ASTM E 162 time to ignition, heat evolved ester resin where the total filler content was kept
and time to specific distances indicated that the at 60%.
composite was progressively less fire resistant 3) Since desired results were not obtained in this
with increasing quantities of APP. series of testing, it is suggested that a formula
5) The maximum smoke ratings, according to the containing APP be repeated using less ATH. If
ASTM E 662 results, were progressively higher in positive results were obtained, the use of APP in
values as the quantity of APP increased. The composites could be an important raw material in
smoke density results at the 1.5 and 4.0 minute fiberglass reinforced composites.
intervals varied significantly.
6) Based on the BSS 7239 test results, the 60%
ATH composite was the best performer.
Fire Retardant Polyester Resin Formulations, continued

Figure B
RESIN LIQUID PROPERTIES

PROPERTY Firepel ® K133-AAA-00

NEAT
FIREPEL® APP12.5/ APP25/
K133-AAA-00 60%ATH
ATH 47.5 ATH 35
C Brookfield Viscosity Spindle #1 @ 50 rpm,
0.018 (18) 0.1 (100) 0.12 (120) 0.185 (185)
al second (cps)

Figure C
Cast Chemical Properties

PROPERTY NEAT Firepel® K133-AAA-00

Tensile Strength, Mpa (psi) 68 (9,900)
Tensile Modulus, Gpa (psi) 3.4 (490,000)
Elongation, % 2.4
Flexural Strength, Mpa (psi) 106 (15,400)
Flexural Modulus, Gpa (psi) 3.8 (550,000)
Heat Distortion Temperature, °C (°F) 85 (185)
Barcol Hardness (934) 45

Figure D
GLASS FIBER COMPOSITE MECHANICAL PROPERTIES

PROPERTY Firepel® K133-AAA-00

NEAT* 60% ATH*
Tensile Strength, Mpa (psi) 107(15,600) 7.9(11,500)
Tensile Modulus, Gpa (psi) 90(1,300,000) 137(2,000,000)
Elongation, % 1.4 1.3

Flexural Strength, Mpa (psi) 165(24,000) 134(19,500)

Flexural Modulus, Gpa (psi) 7.6(1,100,000) 11.7(1,700,000)

Barcol Hardness (934) 45 62

Glass Content, % 30 16
* Composite made with 1 ply of 450 grams per square meter mat (1.5 ounce per square foot)
Fire Retardant Polyester Resin Formulations, continued

Figure E
ASTM E 84 RESULTS
SURFACE BURNING CHARACTERISTICS OF BUILDING MATERIALS USING NON HALOGENATED
GENERAL PURPOSE POLYESTER RESIN COMPOSITE
(# of samples-1)
TEST RESULTS

Firepel® K133-AAA-00
APP12.5/ APP25/
60%ATH
ATH 47.5 ATH 35
Flame Spread 25 40 25
Smoke Development 65 160 250

Figure F
ASTM E 162 RESULTS
SURFACE FLAMMABILITY OF MATERIALS USING A RADIANT ENERGY SOURCE USING
NON HALOGENATED GENERAL PURPOSE POLYESTER RESIN COMPOSITE
(# of samples-4)

TEST RESULTS

Firepel ® K133-AAA-00
APP12.5/ APP25/
60%ATH
ATH 47.5 ATH 35
Time to ignition, seconds 71 51 44
% Standard deviation 14 4.8 7.9
Baseline temperature, °C 190 185 185
Maximum temperature, °C 245 276 291
% Standard deviation 1.6 3.2 4.8
Temperature Rise, °C 55 91 106
% Standard deviation 7.4 9.8 13
Time to 7.6 cm (3 inches), minutes 2.7 2.0 2.0
Standard deviation 30 8.2 5.7

Time to 15.2 cm (6 inches), minutes 4.7 2.9 3

% Standard deviation 32 8.8 4.3

Time to 22.8 cm (9 inches), minutes 8.3 4.5 5.0
% Standard deviation 24 3.0 3.8
Heat evolution factor, Q 8.8 14.4 17
% Standard deviation 8 9.8 13
Flame spread factor, Fs 2.2 3.0 3.0
% Standard deviation 18 4.9 5.2
Fire Retardant Polyester Resin Formulations, continued

Figure G
ASTM E 662 RESULTS
SPECFIC OPTICAL DENSITY OF SMOKE GENERATED USING NON HALOGENATED GENERAL PURPOSE POLYESTER
RESIN COMPOSITE
(# of samples-3)

TEST RESULTS
Firepel® K133-AAA-00
APP12.5/ APP25/
60%ATH
ATH 47.5 ATH 35
NON FLAMING EXPOSURE
Maximum smoke density 40 89 134
% Standard deviation 17 85 6.5
Smoke density after 1.5 minutes 0.2 0.14 0.03
% Standard deviation 60 82 173
Smoke density after 4.0 minutes 2.0 0.47 1.0
% Standard deviation 40 84 120
FLAMING EXPOSURE
Maximum smoke density 61 106 163
% Standard deviation 28 18 20
Smoke density after 1.5 minutes 1.3 0.43 2.6
% Standard deviation 18 97 91
Smoke density after 4.0 minutes 16 8.5 23
% Standard deviation 41 37 10

Figure H
TOXIC GAS GENERATION BSS 7239 FLAMING MODE RESULTS
USING NON HALOGENATED GENERAL PURPOSE POLYESTER RESIN COMPOSITE
(# of samples-1)

RESULTS
TEST
Firepel® K133-AAA-00

60%ATH APP12.5/ATH 47.5 APP25/ATH 35

Hydrogen Cyanide (HCN),
<2 4 7
ppm
Carbon Monoxide, (CO),
67 275 290
ppm

Nitrous Oxides, (NOx), ppm <2 35 60

Sulfur Dioxide, (SO2), ppm <1 ND ND

Fire Retardant Polyester Resin Formulations, continued

Figure I
ASTM E 1354 RESULTS
OXYGEN CONSUMPTION CALORIMETER USING NON-HALOGENATED GENERAL PURPOSE POLYESTER RESIN COMPOSITE

TEST RESULTS
Firepel ® K133-AAA-00
APP 12.5/ APP
ATH 47.5 25/ ATH 35
60% ATH
Time to sustained ignition, seconds 63 76 59
% Standard deviation 5 11 3.9
Average peak heat release rate, kw/m2 341 358 314
% Standard deviation 6.7 12 2.9
Average heat release rate after 60 seconds, kw/m2 235 258 262
% Standard deviation 11 3.0 2.5
Average heat release rate after 180 seconds, kw/m2 138 143 171
% Standard deviation 3.4 3.7 3.5
Average heat release rate after 300 seconds, kw/m2 104 113 126
% Standard deviation 2.7 3.8 5.1
Total heat release, mj/m2 27 27 33
% Standard deviation 5.2 5.0 3.9
Average effective heat of combustion, mj/kg 17 17 21
% Standard deviation 4.7 8.8 1.8
Smoke obscuration, average specific extinction area, m2/kg 433 498 642
% Standard deviation 0.8 6.9 4.3
Mass Loss, % 50.6 44.8 42
% Standard deviation 0.8 3.7 1.4