This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Strengthening of Plastics”.
1. ___________ increases with increasing molecular weight of polymer.
a) Degree of entanglement
b) Flexibility
c) Cracking
d) Creep
View Answer
Explanation: When molecular weight increases, the degree of entanglement of polymer chains increases. It is because of increase in length of polymer chains. While flexibility, cracking and creep decrease.
2. ____________ possess strong intermolecular bonding.
a) Thermoplastic
b) Elastomer
c) Liquid resin
d) Thermosetting plastic
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Explanation: Thermosetting plastics possess strong intermolecular bonding. These have cross linking. These don’t soften on reheating.
3. What doesn’t favor the strengthening of polymers?
a) Addition of glass fibers
b) Addition of polar groups in the chain
c) Addition of plasticizers
d) Addition of bulky side groups in the chain
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Explanation: Plasticizers soften the polymer. Addition of glass fibers on the other hand provides composite strengthening. Addition of polar and bulky size groups in polymer main chain also causes strengthening.
4. What is the effect of increasing molecular weight on melting temperature of polymer?
a) Increases linearly
b) Increases non-linearly
c) Decreases exponentially
d) Decreases linearly
View Answer
Explanation: With an increase in molecular weight of polymer, secondary intermolecular bonds increase. Hence melting point of polymer is increased. It increases linearly.
5. What favors strengthening by crystallinity?
a) Trans type structure
b) Cross linking
c) Branching
d) Copolymerization
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Explanation: Trans type structure favours strengthening by crystallinity whereas branching, cross-linking and co-polymerization increases the distance between chains and decreases crystallinity.
6. Strengthening increases with ____________ in polymers.
a) Increase in crystallinity
b) Decreases in molecular weight
c) Decrease in bulky groups
d) Increase copolymerization
View Answer
Explanation: Strengthening increases with crystallinity in polymers. Copolymerization decreases crystallinity. Molecular weight and bulky groups also increase strengthening.
7. Which of the following polymer shows maximum strength?
a) PE
b) PP
c) PVC
d) PS
View Answer
Explanation: Polystrene shows maximum strength than Polyethene (PE), Polypropylene (PP), Polyvinyl chloride (PVC). And the chemical formula of the monomer is (C6H5)CH=CH2.
8. Which of the following property of a polymer decreases with an increase in crystallinity?
a) Tensile strength
b) Impact toughness
c) Stiffness
d) Creep strength
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Explanation: Impact toughness of a polymer decreases with an increase in crystallinity whereas tensile strength, stiffness and creep strength increases with crystallinity.
9. The degree of crystallinity doesn’t exceed ___________ in polymers.
a) 10%
b) 30%
c) 60%
d) 80%
View Answer
Explanation: The degree of crystallinity can be achieved as high as 80% in polymers. Polymers can’t be 100% crystalline. In polymers only some regions are crystalline.
10. The intermolecular bending forces are ___________ in nylon 6,6 because of the ___________ bonding.
a) Stronger, covalent
b) Stronger, H bonding
c) Weaker, ionic
d) Weaker, H bonding
View Answer
Explanation: Nylon 6,6 shows very good mechanical properties. It is due to strong intermolecular bonds. These are hydrogen bonds.
11. Nylon 6,6 have a higher degree of crystallinity than Polyethylene.
a) True
b) False
View Answer
Explanation: Intermolecular bonding forces are strong in nylon 6,6. It is because of hydrogen bonding. That’s why nylon 6,6 has higher crystallinity than PE.
12. Low-density Polyethylene shows a higher degree of crystallinity than High-density Polyethylene.
a) True
b) False
View Answer
Explanation: High-density Polyethylene has a higher degree of crystallinity than Low-density Polyethylene. It is due to a lower degree of branching in HDPE than LDPE.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
To practice all areas of Mechanical Behaviour & Testing of Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.
