Anna University Polymer Structure and Property Relationship Exam Paper



IV Semester Polymer Technology


Time : Three hours                                                                        Maximum : 100 marks

Answer ALL questions.

PART A — (10 ´ 2 = 20 marks)

1. Distinguish between LDPE & LLDPE.

2. Why do thermosets resist heat and creep better than thermoplastics?

3. Draw stress–strain curves for (a) NR (b) Nylon (c) Phenolic resin.

4.  Why are the following polymers tough : (a) HIPS (b) Nylon?

5. Comment on Tg/Tm ratios in polymers.

6. How do Tgs of SBR & SBS differ?

7. Define : power loss. What is its implication?

8. Why is polyethylene not clear?

9. Can you define ‘Polarity’ in terms of a measurable property? Explain.

10. Which types of polymers can have flame retardancy?

PART B — (5 ´ 16 = 80 marks)

11. (i)      What are the necessary structural features for polymers with (a) high heat resistance (> 200 ºC) (b) good low temperature resistance.                                                  (4 + 4)

             (ii)     What is the significance of Tg on Rubbers, plastics and fibres? How do structural features affect Tg of a polymer?                       (2 + 6)

12. (a)     (i)      How do branching, cross linking, facility affect polymer properties?

                       (ii)    Poly ethylene and a few other polymers have very low Tgs but still do not behave as rubbers. Why? How can you obtain ethylene based rubbers?

                       (iii)   Explain the mechanical properties of various types of copolymers.
(6 + 6 + 4)


             (b)     (i)      Discuss the various transitions which occur in PE, NR polyurethane thermoplastic elastomers and polycarbonate.

                       (ii)    Discuss the importance of calorimetric properties of polymers.
(12 + 4)

13. (a)     How are tensile strength, modulus, impact strength and creep affected by chemical structure?                                                    (16)


             (b)     (i)      How does chemical structure affect stress–strain relationships in various  types of polymers?

                       (ii)    Compare fatigue resistance of NR and SBR.

                       (iii)   While carbon black reinforces a rubber, it does do so for a plastic. Explain.                                (8 + 4 + 4)

14. (a)     (i)      Explain the importance of dielectric constant and break down voltage.

                       (ii)    How temperature and frequency affect dielectric properties?

                       (iii)   Which additives affect electrical properties? Explain.

                       (iv)    Write a note on conducting polymers.                           (4 + 4 + 4 + 4)


             (b)     (i)      Compare optical properties and utilities of PS, PMMA, PC.

                       (ii)    How are haze and gloss affected by chemical structures?

                       (iii)   How do LDPE, HDPE, BOPP differ in optical properties? (6 + 6 + 4)

15. (a)     (i)      How are solubility parameters for polymers and solvents found? Explain the importance of solubility parameter.

                       (ii)    How does chemical structure affect solubility parameters in polymers and solvents?

                       (iii)   How is solvent resistance affected by chemical structure? (6 + 6 + 4)


             (b)     Write a note on chemical reactivity of polymers and explain how they are affected by chemical structure?                                  (16)



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