Module 3
1. Write down the principle of roasting. Compare the calcination process with roasting.
2. List down the advantages of calcination.
3. Compare between the processes of crushing and grinding.
4. Classify roasting .Give example of each.
5. Define dead roast. Illustrate the factors affecting roasting.
Module4
1. What are the differences between :
2. Thermoplastics & thermoset polymers
3. Rubbers, plastics and fibres
4. LDPE & HDPE
5. ISOTACTIC & ATACTIC PS
6. Why do find PS, PF and PMMA as very rigid and brittle? Draw the Stress Vs. Strain graphs for
these polymers and comment on the trend of these.
7. Calculate PDI of the polymer having following values:
Ni Mi
12500 350000
2055 45000
13500 530000
10500 403000
8. What are the advantages and limitations of wide/narrow molecular weight distribution
of polymers in respect to mechanical properties?
9. Draw MWD graph and explain the position of Mn and Mw in that .
10. Why do we see various grades of PE showing variation in density and crystallinity?
11. Why are PE and PP crystalline but PMMA is amorphous?
12. Write down the chemical structure of repeat unit of polyvinyl alcohol. Calculate the
average molecular weight of this polymer assuming equimolar system and number of
repeat unit as 12000, 25000, 31000 for different fractions.
13. Why are PS and PMMA rigid and look transparent like glass?
14. What are the factors controlling crystallinity index of polymamides?
15. Why do we see some polymer rubbery and not elastic? What is the basis of rubber
elasticity?
16. Why is PE soluble in xylene ,PMMA in toluene but nylon 6 is not soluble in these
solvents?
17. How does branching in polymers affect its solubility and density?
18. Give example of water soluble polymers that are used as adhesive. What is the reason
of its adhesive behavior?
19. Which polymers are used in paint industries to manufacture water based paints?
20. Write down the chemical structure of polybutyl acrylate and Polymethyl methacrylate.
21. Explain the trends of glass transition temperature and melting point of the following
polymers:
Polymer Tg (°C) Tm (°C)
Polypropylene (PP) − 25 170
Acrylonitrile butadiene styrene (ABS) 100 125
Polycarbonate (PC) 149 225
Nylon 6,6 49 250
22. “Crystalline polymers are hazy”. Explain the reason of such phenomenon.
23. What are the factors controlling solubility of polymers in solvents? Why do we see some
polymers never soluble in any solvent? Explain this with suitable examples.
24. Which polymer is more soluble in xylene than the other among the following pair:
LDPE/HDPE ?
25. Both PVC and PVDC act as weak acid in solution but PVC is soluble in THF while PVDC is
soluble in N-methylpyrrolidone. Explain the fact.
26. Why does Tg of PVC (76.8 C) vary with variation in additive concentration?
27. What are the factors affecting glass transition point of polymers? How does free volume of
polymers vary with chemical structure of repeat unit? Give some examples.
28. Why do we see higher Tg for PC greater than PE though PC possesses high free volume?
29. What are the thermodynamic conditions for solubility of a polymer in a solvent?
30. What is the significance of interaction parameter(chii) and solubility parameter?
31. Draw the stress strain graph of polymers and explain the nature of such graph for PS, PP,
HIPS, PF, Polyacetal resins.
32. What is the effect of copolymerization on mechanical properties ? Explain the fact for ABS,
EPDM in comparison to PS and PE/PP.
33. How does Tg depend on molecular weight of polymer?
34. Why do some polymers not exhibit glass transition temperature?
Ans: a) Some polymers being highly crystalline and therefore do not possess glassy
state and melts sharply at a temperature (Tm).b) Also for some amorphous polymers,
specific heating rate during experiment, matters a lot. At lower rate of heating they
may show Tg but at higher rate of heating they do not.
35. What is the function of plasticizer? Explain the effect of internal and external
plasticization on glass transition point of polymers.
36. Describe the effect of processing conditions on the crystallinity and glass transition
point of polymers.
37. How does natural rubber undergo crystallization?
38. Write the manufacturer’s /supplier’s name of following polymers in India:
HDPE, LDPE, PP, PS, PVC, PMMA, PET, PC, ABS, HIPS
39. Both PC and SBR are tough polymers, but PC is glassy at room temperature while
SBR is rubber. Explain the fact with specific reasons.
40. When we dip PF in acetone it does not dissolve even after 7 days though the solubility
parameters of them match. Why?
