Polymer Flow and Viscoelasticity - Polymer Rheology - Engineering Sciences Previous Year Questions

1

2008 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2008

Most polymers exhibit Newtonian behaviour at

A

high temperature

B

low shear rate

C

high molecular weight

D

low filler content

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2

2008 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2008

The extension ratio of an elastomer deformed to 10 times is

A

2

B

5

C

9

D

11

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3

2008 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2008

For a viscoelastic material behaving as Maxwell model, the modulus at its relaxation time under constant strain reduces to

A

36.8 % of the initial value

B

63.2 % of the initial value

C

66.7 % of the initial value

D

33.3 % of the initial value

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4

2009 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2009

Which of the following trends is the most appropriate for a thixotropic fluid ?

A

Viscosity increases with increase in the rate of shear.

B

Viscosity increases with increase in the time of application of shear.

C

Viscosity decreases with increase in the time of application of shear.

D

Viscosity increases with decrease in the rate of shear.

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5

2009 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2009

The ratio of the complex dynamic modulus to the storage modulus of a polymer system with a phase angle of 45° is

A

0

B

$1 - i$

C

$1 + i$

D

$1 \pm i$

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6

2009 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2009

Strain, \( \gamma \), in a polymer melt varies with time on application of stress \( s \) by the following relation : \[ \eta \frac{d\gamma}{dt} + G\gamma = s \] If a steady shear stress, \( s_0 \), is applied, the strain at the steady state, \( \gamma_0 \), is given by

A

\(\frac{s_0}{G} \)

B

\(\frac{s_0}{\eta} \)

C

\(s_0 G \)

D

\(s_0 \eta \)

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7

2010 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2010

The change of shear stress with shear rate of a polymer melt as shown in the figure below indicates

A

Viscosity increase with increase in shear rate

B

Viscosity decrease with increase in shear rate

C

Viscosity remaining independent of shear rate

D

Viscosity oscillation with increase in shear rate

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8

2011 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2011

As the molecular weight (M) increases beyond the critical molecular weight (M_c), the zero shear viscosity of a polymer melt becomes proportional to

A

M^{0.5}

B

M^{3.4}

C

M^{1.0}

D

M^0

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9

2011 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2011

In the log (viscosity) versus log (shear rate) behaviour of polymer melts, the upper (\(\mu_{upper}\)) and lower (\(\mu_{lower}\)) Newtonian viscosities are related as

A

\(\mu_{upper}\) and \(\mu_{lower}\) versus shear rate are connected by discontinuous curve

B

\(\mu_{upper} > \mu_{lower}\)

C

\(\mu_{upper} < \mu_{lower}\)

D

\(\mu_{upper} = \mu_{lower}\)

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10

2012 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2012

If the above sample is stressed to 2 MPa initially, then the time required to relax the stress to 1 MPa will be

A

31.6 days

B

41.6 days

C

51.6 days

D

61.6 days

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11

2013 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2013

What is the relaxation time constant for this material?

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12

2013 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2013

Stretching of rubber leads to

A

decrease in alignment of polymer chains

B

increase in alignment of polymer chains

C

no change in alignment of polymer chains

D

decrease in strength of rubber

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13

2013 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2013

The constitutive equation (relation between stress \(\sigma\) and strain \(\gamma\) in which overdot represents the time derivative) for the fluid is:

A

\(\sigma = G\gamma + (\eta_1+\eta_2)\dot{\gamma}\)

B

\(\sigma = G\gamma + (\eta_1-\eta_2)\dot{\gamma}\)

C

\(\dot{\gamma} = \frac{\dot{\sigma}}{G} + \left(\frac{1}{\eta_1} + \frac{1}{\eta_2}\right)\sigma\)

D

\(\dot{\gamma} = \frac{\dot{\sigma}}{G} + \frac{\sigma}{\eta_1+\eta_2}\)

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14

2015 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2015

The viscoelastic behavior of a plastic is represented by spring and dashpot elements having constants of 2 GN m⁻² and 90 GN s m⁻², respectively. If a constant stress of 12 MN m⁻² is applied, the strain predicted by Maxwell model after 50 s is _____ %.

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15

2017 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2017

Match plots 1-4 given in the figure below with the correct flow behavior of polymeric fluid listed as P, Q, R & S:
P. Newtonian
Q. Shear thickening
R. Pseudoplastic
S. Bingham plastic

A

P-4; Q-2; R-3; S-1

B

P-4; Q-3; R-2; S-1

C

P-4; Q-3; R-1; S-2

D

P-1; Q-3; R-2; S-4

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16

2017 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2017

Refer the shear stress – shear rate plot shown in the figure below. Match the lines (Column I) with appropriate rheological behavior (Column II).
Column I
P. Line 1
Q. Line 2
R. Line 3
S. Line 4
Column II
1. Dilatant
2. Newtonian
3. Pseudoplastic
4. Bingham plastic

A

P-2, Q-3, R-4, S-1

B

P-1, Q-3, R-4, S-2

C

P-2, Q-4, R-3, S-1

D

P-4, Q-3, R-2, S-1

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17

2017 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2017

The relaxation time for a rubber band at 23 °C is 60 days. If it is stressed to 2 MPa initially, then the time required before the stress relaxes to 1 MPa is ______ days (round off final answer to two digits after decimal point).

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18

2018 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2018

A plot of strain (%) versus time of a polymer is given below. Based on this plot and the properties as mentioned below, find out the correct combination.
1 = Viscoelastic deformation; 2 = Elastic deformation
3 = Viscoelastic recovery; 4 = Elastic recovery

A

P-1; Q-4; R-2; S-3

B

P-2; Q-3; R-4; S-1

C

P-3; Q-1; R-2; S-4

D

P-2; Q-1; R-4; S-3

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19

2019 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2019

A linear amorphous polymer has a \(T_g\) of +10 °C. At 28 °C, it has a melt viscosity of \(4 \times 10^8\) poise. The viscosity of the polymer at its \(T_g\) is ______ \(\times 10^{13}\) poise (round off to one decimal place).

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20

2021 · Engineering Sciences · Polymer Rheology · Polymer Flow and Viscoelasticity

Engineering Sciences (XE) 2021

Equal and opposite forces of a constant magnitude \( F \) are applied at the two ends of a thin elastomeric rod, which is held at a temperature \( T_1 \) (\( T_g < T_1 < T_m \)), where \( T_g \) and \( T_m \) are the glass transition temperature and melting temperature respectively. If the temperature is increased to \( T_2 \) (\( T_g < T_2 < T_m \) and \( T_2 > T_1 \)), the rod will ____________________.

A

expand along the loading direction and the transverse direction

B

shrink along the loading direction

C

remain dimensionally unaltered

D

expand only along the loading direction

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