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2003 Course Polymer Structure & Property Relationship

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Total No. of Questions : 12] [Total No. of Pages : 4 P1317 [3664]-293 B.E. (Polymer) POLYMER STRUCTURE AND PROPERTY RELATIONSHIP (2003 Course) Time : 3 Hours] [Max. Marks : 100 Instructions to the candidates: 1) Answer three questions from Section - I and three questions from Section - II. 2) Answers to the two Sections Should be written in separate books. 3) Neat diagrams must be drawn wherever necessary. 4) Figures to the right indicate full marks. 5) Your answers will be valued as a whole. 6) Assume suitable data, if necessary. SECTION - I Q1) a) Explain the reason for variation in density and melting point of PP, LDPE & HDPE. [5] b) Write a short note on how following factors are affected due to chemical composition of polymers [8] i) Density. ii) Flammability. iii) Charring. iv) Moisture absorption. v) Wheatherability. Out of N - 66 & N - 6, which absorb more moisture and why? [3] What is an isocynate linkage? [2] c) d) OR Q2) a) Explain the bonds carbon atom makes with other atoms & thus the properties. [8] b) Write a short note on LCP. [5] c) Write a note on the bonds formed by oxygen atom & its effect on properties. [5] P.T.O. Q3) a) Why inspite of having amide linkages, PU have low melting point than polyamide. [3] b) Write a short note on adhesion. [5] c) What modifications can be suggested to soften the brittle nature of PS. [5] d) What factors will give any polymer temperature stability. [3] OR Q4) a) b) c) d) Methyl group is present in Natural Rubber as well as PP. Explain its effect on both. [3] Is PVC amorphous or crystalline. Why PVC has high Tg than PVDC. [3] Explain surface tension and role of chemical groups in bonding enhancement. [7] Explain why modulus of Nylon is very high than polyolefins. [3] Q5) a) Give the role of stabilizers and antioxidants when added to polymer, and how do they function. [6] b) What is meaning of NMWD & BMWD. How can they be found out? In case of blow molding which of the two will give better result & why? [7] Give effect of plasticizer on polymers. [3] c) OR Q6) a) Explain following terms : i) Dielectric nature. ii) [12] Dielectric constant. iii) Capacitance. iv) Dielectric loss and v) Dissipation factor. Also explain what all parameters have effect on dielectric constant. b) Why presence of halogens makes a polymer selfextinguishable. [3664]-293 2 [4] SECTION - II Q7) a) b) c) With egs. show what is the effect of following factors on flexibility of polymer (any 3) [6] i) Branching. ii) Tacticity. iii) Polarity. iv) Side groups. What is meant by molecular flexibility. Explain what is potential energy barrier for rotation. [6] Give the effect of lengthening of n-alkyl groups on stearic hinderance giving egs. [6] OR Q8) a) b) With egs. give the effect of structure on freedom of rotation. [10] Give the role of tensile strength with molecular flexibility. Also give its effect w.r.t. modulus and percentage elongation. [5] What is 1st & 2nd order phase transition. [3] What are the factors that favour crystallisation in a polymer. [8] b) Explain terms like fringed micelle model, lamella & sphermlite. [5] c) Explain role of symmetry towards crystallisation. [3] c) Q9) a) OR Q10)a) Explain the effect of crystallinity on processing techniques like : [10] i) Injection molding. ii) Thermoforming. iii) Heat sealing. iv) Orientation & v) b) Fiber forming. What is the difference between crystallisation and orientation. Do both the processes lead to same effect on polymer properties. Explain [6] [3664]-293 3 Q11)a) What is meant by intermolecular bonding & significance of length & strength of primary & secondary covalent bonds. [5] b) Explain all those parameters that result/depend on eventually breaking of primary and secondary covalent bonds. [4] c) Explain why larger and heavier atoms and molecules exhibit stronger dispersion forces than small & lighter ones. [4] d) Write a short note on H-bonding. [3] OR Q12)a) What is meant by CED and how can it be found. [5] b) Explain different types of forces that lead to stronger inter molecular forces. Explain any one in detail. [8] c) Explain with eg. the fact that shape of molecules affect the magnitude of dispersion forces and thus properties. [3] vvvv [3664]-293 4

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