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Polymer Structures Tutorial

This document contains a tutorial on polymer structures, characteristics, applications and processing with 12 problems related to calculating properties of various polymer composites. It discusses concepts like molecular weight, degree of polymerization, cross-linking of polymers, weight and mole fractions of copolymers, efficiency of fiber reinforcement, effects of fiber amount/arrangement on strength, density calculations, modulus of elasticity, strength, load transfer in composites, and effects of temperature on thermoplastic properties.

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Abood Atiyat
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82 views2 pages

Polymer Structures Tutorial

This document contains a tutorial on polymer structures, characteristics, applications and processing with 12 problems related to calculating properties of various polymer composites. It discusses concepts like molecular weight, degree of polymerization, cross-linking of polymers, weight and mole fractions of copolymers, efficiency of fiber reinforcement, effects of fiber amount/arrangement on strength, density calculations, modulus of elasticity, strength, load transfer in composites, and effects of temperature on thermoplastic properties.

Uploaded by

Abood Atiyat
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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KXEX1110: Basic Materials Science

Lecturer: Dr. Wong Yew Hoong


Tutorial 9:
Polymer Structures
Characteristics, Applications and Processing of Polymers

1. A nylon 6,6 has an average molecular weight of 12,000 g/mol. Calculate the average

degree of polymerization. M.W. = 226 g/mol.

2. Calculate the average molecular weight Mm for a thermoplastic that has the following

weight fractions fi for the molecular weight ranges listed:

3. How much sulfur must be added to 70 g of butadiene rubber to cross-link 3.0 percent of

the mers? (Assume all sulfur is used to cross-link the mers and that only one sulfur atom is

involved in each cross-linking bond.)

4. An ABS copolymer consists of 25 wt % polyacrylonitrile, 30 wt % polybutadiene, and 45

wt % polystyrene. Calculate the mole fraction of each component in this material.

5. For a fiber reinforced composite, the efficiency of reinforcement, η is dependent on fiber

length, l according to

where x represents the length of the fiber at each end that does not contribute to the load

transfer. Make a plot of η versus l to l = 50 mm assuming that x = 1.25 mm. What length

is required for 0.90 efficiency of reinforcement?

6. How does the amount and arrangement of the glass fibers in fiberglass reinforced plastics

affect their strength?

1
KXEX1110: Basic Materials Science
Lecturer: Dr. Wong Yew Hoong
7. A unidirectional carbon-fiber-epoxy-resin composite contains 68 percent by volume of

carbon fiber and 32 percent epoxy resin. The density of the carbon fiber is 1.79 g/cm 3 and

that of the epoxy resin is 1.20 g/cm3. (a) What are the weight percentages of carbon fibers

and epoxy resin in the composite? (b) What is the average density of the composite?

8. Calculate the tensile modulus of elasticity of a unidirectional carbon-fiber-reinforced-

plastic composite material that contains 64 percent by volume of carbon fibers and is

stressed under isostrain conditions. The carbon fibers have a tensile modulus of elasticity

of 54.0 × 106 psi and the epoxy matrix a tensile modulus of elasticity of 0.530 × 106 psi.

9. If the tensile strength of the carbon fibers of the 64 percent carbon-fiber-epoxy composite

material of Prob. 12.23 is 0.31 × 106 psi and that of the epoxy resin is 9.20 × 103 psi,

calculate the strength of the composite material in psi. What fraction of the load is carried

by the carbon fibers?

10. Is it possible to produce a continuous and oriented aramid fiber – epoxy matrix composite

having longitudinal and transverse moduli of elasticity of 5 x 106 psi and 7.5 x 105 psi

respectively? Why or why not? Assume that the elastic modulus for epoxy is 4.93 x 10 5

psi.

11. Explain why thermosetting platics have in general high strengths and low ductilities.

12. How does increasing the temperature of thermoplastics affect their strength? What

changes in bonding structure occur as thermoplastics are heated?

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