BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST

ADITYA BIRLA GROUP ADITYA BIRLA CENTRE ‘C’ WING 1ST
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJ) I
BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST

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BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI SEMESTERII 200708
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BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI (RAJASTHAN)

1st Semester (2007-2008)

Comprehensive Examination

Course No.: CHE G522 Date: 01-12-2007

Course Title: Polymer Technology Duration: 2-5:00 p.m

Room No.: MM: 40

Note: Part –A Closed Book (20 Marks, approx duration: 1 hour 30 mins, Total Questions 1-9)

Part –B Open Book (20 Marks, approx duration: 1 hour 30 mins, Total Ques 1-7)

Part –A Closed Book

  1. Answer the following questions. [1+0.5+1=2.5]

    1. Why is it important to calculate the ceiling temperature of the polymers?

    2. Name the stabilizer used for transparent thermoplastics to protect against yellowing.

    3. What does high plasticization efficiency indicate during plasticization of polymers?

  2. Starting from the power law model, derive the die characteristics for the capillary rheometry. [3]

  3. A polymer sample with number average molecular weight (BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST ) and weight average molecular weight (BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST ) is known. The sample is contaminated with 3% by weight of an impurity. What effect does this contamination have on the average molecular weight determined by the light scattering and by membrane osmometry? [2]

  4. Explain the following. [1+1]

    1. Polyisoprene degradation by UV light.

    2. Working Principle of Differential Scanning Calorimetry (DSC).

  5. Explain the second order thermal transitions to obtain the Tg of polymers. [3]

  6. The relative flow times (t/t0) of a poly (methyl methacrylate) polymer in choloroform are given below:

    1. Determine intrinsic viscosity ([η]) of the polymer sample. [1.5]

    2. Calculate BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST using Mark Houwink parameter of a = 0.8 and K = 3.4X10-5 dl/g. [1.5]

c (g/dl) t/t0

0.20 1.29

0.40 1.632

0.60 2.026

  1. Which commercial polymer undergoes non-chain scission reactions? Explain w.r.t specific reaction. [1]

  2. Derive the equations for mole fractions of monomer in copolymer formed, in terms of reactivity ratios in co polymerization reaction. [3]

  3. In a free-radical polymerization reaction what would be the effect of increasing [I]o four times at constant [M]o upon: [2]

    1. the total radical concentration at steady state

    2. no. average degree of polymerization

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI (RAJASTHAN)

1st Semester (2007-2008)

Comprehensive Examination

Course No.: CHE G522 Date: 01-12-2007

Course Title: Polymer Technology Duration: 2-5:00 p.m

Room No.: MM: 40

Part –B Open Book


  1. The table given below gives the mean flow times (s) in a suspended level viscometer recorded for solutions of a monodispersed sample PS at various concentrations (c) in cyclohexane at 34o C. [4]

Table - 1

CX 103 g/cm3

t (s)

0

151.8

1.586

158.5

5.553

178.6

7.403

189.6

8.884

199.5

The intrinsic viscosities [η] of other 3 PS samples A, C, D and E were evaluated under the same conditions and are given in the following table along with BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST values of all the samples determined by simple viscometer.

Table - 2

PS Sample

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE PILANI (RAJASTHAN) 1ST g/gmole

[η] cm3/g

A

37000

15.77

B

102000

-

C

269000

42.56

D

690000

68.12

E

2402000

79

Calculate

  1. intrinsic viscosity of sample B

  2. Using the data in Table-2 calculate the Mark Houwink parameters for PS in cyclohexane at 34o C.


  1. Assume that a polyesterification is conducted in the absence of solvent or catalyst and that the monomers are present in stoichiometric ratios. Calculate the time (sec) required obtaining a number average degree of polymerization of 50 given that the dicarboxylic acid concentration is 3 mol/ L and that the polymerization rate constant is 10-2 L/ mol/sec. [3]


  1. A polymer has a crystalline growth parameter of 2 and a rate constant of 10-2/ s2 at 1000 C. The polymer is melted and quenched at 1000C and is allowed to crystallize isothermally. After 10 seconds, what is the % crystallinity of the sample? [2]





  1. What are the characteristics which make polymer reactors different from the other reactors? [2]


  1. The glass transition temperature (Tg) of a linear polymer with Mn =2300 was found to be 1210C. The value of Tg increased to 1530C for a sample of the same linear polymer with Mn = 9000. The branched version of the same polymer with Mn = 5200 was found to have a Tg of 1150C. Determine the average number of branches on the molecules of the branched polymer. [5]

  2. State the methods you would use to determine:

    1. Mn for samples of poly(ethylene glycol) with values in the range 4 × 102 to 5 × 103 g/mol.

    2. Mn for samples of poly(acrylonitrile) with values in the range 5 × 104 to 2 × 105 g/mol.

    3. The polydispersity indices of samples of polystyrene with molecular weight in the range 104 to 106 g/mol.

For each method give the reasons for your choice, name a solvent that would be suitable for the measurements and discuss briefly possible errors in the determinations. [4]



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