250+ TOP MCQs on Polystyrene and Answers

Polymer Engineering Multiple Choice Questions on “Polystyrene”.

1. Which of the following is used as a catalyst for the alkylation of benzene in the process of formation of styrene?
a) AlCl₃
b) MgO
c) FeO
d) TiCl₄

Answer: a
Clarification: The alkylation of benzene involves the use of Friedel-Crafts catalysts AlCl₃ for the formation of ethyl benzene which would further produce styrene.

2. Which of the following can stabilize the vinyl benzene?
a) t-butyl catechol
b) t-butyl hexanol
c) lactone
d) none of the mentioned

Answer: a
Clarification: Styrene, also known as vinyl benzene, is stabilized by the addition of traces of phenolic stabilizer, like t-butyl catechol after it is separated from the dehydrogenated product by distillation. It is then stored in a cold storage for longer-shelf life.

3. How many stages do the bulk polymerization of styrene passes through?
a) 2
b) 1
c) 3
d) 4

Answer: a
Clarification: The bulk or mass polymerization of styrene takes place in two stages. In the first stage, the stabilizer free monomer is polymerized to a low conversion in a CSTR. Then, in the next stage, high conversion takes place in a tower reactor (25-40 ft high and 15 ft diameter) with increasing temperature gradient.

4. What kind of polymer is the commercially used polystyrene?
a) syndiotactic
b) isotactic
c) atactic
d) all of the mentioned

Answer: c
Clarification: Commercial Polystyrene is generally linear atactic polymer, which in amorphous and transparent in nature.

5. Which of the following property of polystyrene is improved, when traces of unreacted monomer is removed?
a) melting point
b) brittleness
c) crystallinity
d) none of the mentioned

Answer: a
Clarification: The melting point or heat distortion temperature is improved from nearly 70 to 100 ᵒC, by removing the last traces of unreacted monomer from the polymer formed.

6. What is the approximate density of polystyrene in g/cm³?
a) 0.96
b) 0.915
c) 1.054
d) 1.5

Answer: c
Clarification: The density of polystyrene is nearly 1.054 g/cm³, which is quite higher than the densities of polyethylene and polypropylene.

7. Polystyrene is not a suitable polymer to be used for injection moulding and thermoforming. State true or false.
a) true
b) false

Answer: b
Clarification: Polystyrene is an ideal polymer to be used for injection moulding and thermoforming, due to its properties like, low moisture absorption, dimensional stability, low moulding shrinkage and good mouldability.

8. Which of the following grade of polystyrene is useful in optical applications?
a) general-purpose (GP-PS)
b) high impact (HIPS)
c) expanded grades
d) none of the mentioned

Answer: a
Clarification: The GP-PS polymer produced is used for optical applications because of its excellent optical properties with high refractive index.

9. What is the effect of the outdoor exposure on polystyrene?
a) lowering of melting point
b) crazing and yellowing
c) increased brittleness
d) none of the mentioned

Answer: b
Clarification: Polystyrene has poor outdoor weathering resistance and it crazes and turns yellow after long use.

10. Which component is present in the high impact polystyrene (HIPS) besides styrene monomer to improve only impact strength of polystyrene?
a) acrylo-nitrile
b) vinyl acetate
c) polybutadiene
d) all of the mentioned

Answer: c
Clarification: HIPS is produced by the emulsion polymerization of monomer with dispersed particles of polybutadiene. The enhancement in impact properties of polystyrene is dependent on the size, concentration and distribution of particles of polybutadiene.

11. Where is the expandable grade of polystyrene useful in?
a) producing foamed products
b) producing rubbery products
c) making optical instruments
d) none of the mentioned

Answer: a
Clarification: The expandable grade of polystyrene is used to produce foamed products. The beads of expanded polystyrene is formed by suspension polymerization of styrene in the presence of volatile organic foaming or blowing agents, like pentane or hexane.

12. Which of the following properties is improved when styrene and acrylo-nitrile are copolymerized together?
a) heat distortion temperature
b) impact strength
c) chemical resistance
d) all of the mentioned

Answer: d
Clarification: To improve the impact strength and the heat distortion temperature of styrene-based polymer, styrene is copolymerized with 20-30% acrylo-nitrile. The copolymer formed has better chemical and solvent resistance, and also better resistance to stress cracking and crazing.

13. Which of the following comonomer can copolymerize with styrene to give out a polymer suitable for making ion-exchange resins?
a) vinyl acetate
b) divinyl benzene
c) acrylonitrile
d) butadiene

Answer: b
Clarification: The polymer based on styrene that is used in making ion-exchange resins is produced in the cross-linked form by suspension polymerization of styrene and comonomer divinyl benzene.

14. What is the percentage value of elongation at break for polystyrene?
a) 1-3%
b) 100-300%
c) 20-130 %
d) 200-240%

Answer: a
Clarification: The value of elongation at break for general purpose polystyrene is 1-3%, which is comparatively very low as compared to other polymers.

15. Which of the following grade of polystyrene is well suited for the purpose of packaging applications?
a) high impact (HIPS)
b) general purpose (GP-PS)
c) expandable
d) all of the mentioned

Answer: c
Clarification: The expandable grade is used to produce foamed products. The smaller beads that are foamed provide better mechanistic properties along with surface finish, which makes its use in custom packaging and insulation purposes.