This set of Polymer Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Techniques of Polymerization-1”.
1. Which of the following initiation mechanism in vinyl polymerization, does not produce a pure polymer?
a) initiator decomposition
b) uncatalyzed thermal initiation
c) uncatalyzed photochemical initiation
d) all of the mentioned
View Answer
Explanation: For uncatalyzed vinyl polymerization done thermally or photochemically, the polymer produced is very pure and free from any contaminants, while the use of initiator leaves the polymer impure due to the presence of traces of initiator in it.
2. What may be the consequence of the uncontrolled vinyl polymerization with excessive rise in temperature?
a) discolouration
b) thermal degradation
c) branching or cross-linking
d) all of the mentioned
View Answer
Explanation: If reaction is left uncontrolled, excessive increase in the temperature at local points called ‘hotspots’ can cause discolouration, thermal degradation, branching of polymers and sometimes even cross-linking, giving rise to the formation of polymer of inferior quality.
3. Why does heat dissipation in bulk polymerization becomes progressively difficult with high conversions?
a) increase in medium viscosity
b) solubilization of polymer in the monomer
c) precipitation of polymer in the monomer
d) all of the mentioned
View Answer
Explanation: The stirring process and heat dissipation become progressively difficult due to gain in viscosity medium or due to solubilization or precipitation of polymer in the monomer, more so in higher conversions.
4. Which of the following monomer mixture is used in bulk polymerization?
a) undiluted monomer
b) monomer –solvent mixture
c) monomer-water mixture
d) none of the mentioned
View Answer
Explanation: Bulk polymerization is the polymerization of undiluted monomer and is the simplest technique of polymer synthesis.
5. How is the solvent in solution polymerization, more useful to overcome the disadvantages of bulk polymerization?
a) it reduces the viscosity gain
b) increases the rate of reaction
c) causes chain transfer
d) all of the mentioned
View Answer
Explanation: The solvent reduces the viscosity gain, thus allowing more efficient stirring of the medium and proper heat dissipation of the heat liberated. The chain transfer to solvent causes a problem for solution polymerization.
6. Which of the following is a demerit of solution polymerization?
a) handling of inflammable solvents
b) recovery of solvent
c) chain transfer to solvent
d) all of the mentioned
View Answer
Explanation: The solution polymerization process often requires the handling of inflammable solvents and the recovery of solvent from the polymer to isolate it. Chain transfer to solvent may also pose a problem as the purity of polymer is affected due to the leftover traces of solvent in the polymer product.
7. Which of the following polymerization system prepared by solution polymerization, is heterogeneous in character?
a) methyl methacrylate in solvent
b) acrylonitrile in organic solvent
c) ethylene in organic solvent
d) all of the mentioned
View Answer
Explanation: In polymerization of acrylonitrile in water or any organic solvent, the solvent is not able to dissolve the polymer being formed and so the system becomes heterogeneour in nature with polymer formation.
8. Which of the following polymerization is also known as pearl polymerization?
a) bulk polymerization
b) solution polymerization
c) emulsion polymerization
d) suspension polymerization
View Answer
Explanation: At the end of the suspension polymerization, the polymer formed appears in the form of tiny beads or pearls, so it is also known as pearl polymerization.
9. What kind of initiators is used in the process of suspension polymerization?
a) oil-soluble
b) water-soluble
c) oil-water insoluble
d) none of the mentioned
View Answer
Explanation: In suspension polymerization, oil-soluble initiators like peroxides, hydroperoxides and azo-compounds are used.
10. Which of the following is used as a stabilizer in suspension polymerization?
a) gelatin
b) peroxides
c) water
d) carbon tetrachloride
View Answer
Explanation: The process of suspension polymerization requires water soluble polymer stabilizers like CMC, PVA or gelatin, etc. to raise medium viscosity and stabilize the suspension.
Sanfoundry Global Education & Learning Series – Polymer Engineering.
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