This set of Polymer Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Polyamides”.
1. Name the polymer formed by the polymerization of ω-amino caproic acid using water as a catalyst?
a) nylon 6
b) nylon 6,6
c) nomex
d) abs
View Answer
Explanation: Nylon 6 is formed by the polymerization of ω-amino caproic acid in the presence of water ( used as a catalyst) and small amount of acetic acid for regulating the chain length.
nNH2−(CH2)5−COOH → [−NH−(CH2)5−CO−]n .
2. What is the monomer pair required for the formation of Nylon 610?
a) ω-amino caproic acid + diamine
b) hexamethylene diamine + adipic acid
c) hexamethylene diamine + sebacic acid
d) hexamethylene diamine + decanoic acid
View Answer
Explanation: The reaction between hexamethylene diamine and sebacic acid gives the polyamide Nylon 610 via formation of an appropriate salt. The reaction is given by-
nNH2−(CH2)6−NH2 + HOOC−(CH2)8−COOH → [−NH−(CH2)6−NH−CO−(CH2)8−CO−]n.
3. Monomer A is reacted with a monomer B in boiling methanol to form a salt. The salt dissolved in water with a little amount of acetic acid is then processed in autoclave at different temperatures and pressure. Monomer A is a bifunctional monomer having amine groups. What is the name of monomer B?
a) adipic acid
b) ω-amino caproic acid
c) undecanoic acid
d) dodecyl lactam
View Answer
Explanation: Monomer A is adipic acid and monomer B is hexamethyelene diamine, which reacts in the given conditions and then processed into an autoclave, where temperature is raised to 220 ᵒC and later pressure is allowed to develop at 250 psi.
4. Which of the following mechanism takes place for the formation of high molecular weight Nylon 6 from caprolactum?
a) anionic mechanism
b) cationic mechanism
c) radical mechanism
d) none of the mentioned
View Answer
Explanation: The polymerization of caprolactum y anionic mechanism follows in the presence of a strong base to for high molecular weight nylon 6.
5. Which of the following polyamides are known as aramids?
a) aliphatic polyamides
b) aromatic polyamides
c) unsaturated polyamides
d) all of the mentioned
View Answer
Explanation: Aromatic polyamides are commonly known as aramids. Aramid fibres are a recent development to be practically used.
6. Which of the following can help in achieving the mechanical properties of nylons?
a) plasticizers
b) nucleating agents
c) mould agents
d) impact modifiers
View Answer
Explanation: The mechanical properties of nylons are largely dependent on the crystallinity of polymers. Thus, such kind of properties can be developed by increasing the degree of crystallinity and spherulite size with the help of nucleating agents.
7. Polyamides have a limited use in the areas where long exposure to temperatures above 70-90 ᵒC is required, due to their tendency of surface oxidation in air. Which heat stabilizer can permit their use even in higher temperatures?
a) sodium salts
b) copper salts
c) potassium salts
d) none of the mentioned
View Answer
Explanation: The addition of nearly 1% of copper salts acts as heat stabilizer and permits the use of polyamides at higher temperatures.
8. Where is the use of nylon films unsuitable, considering the properties required for applications?
a) packaging of food stuffs
b) packaging of drugs
c) for pharmaceuticals
d) none of the mentioned
View Answer
Explanation: Nylon films have an impressing feature of low odour transmission which makes it suitable for use in the packaging of food stuffs, drugs and pharmaceuticals.
9. Which polyamide is formed when polymerization of isophthaloyl chloride and m-phenylene diamine takes place?
a) nomex
b) kevlar
c) nylon 6
d) SBR
View Answer
Explanation: Nomex is an aramide formed by the solution or interfacial polymerization of isophthaloyl chloride and m-phenylene diamine. It has a melting point of 365 ᵒC.
10. What is the tensile strength exhibited by the moulded objects prepared from nylons?
a) 12000 psi
b) 1200 psi
c) 60000 psi
d) 6000 psi
View Answer
Explanation: The moulded objects prepared from nylons have a tensile strength nearly about 12000 psi, which is far higher than the objects from other polymers.
11. Which of the following monomer pair polymerizes to give an aramide?
a) hexamethylene diamine + sebacic acid
b) terephthaloyl chloride + phenylene diamine
c) hexamethylene diamine + adipic acid
d) none of the mentioned
View Answer
Explanation: Aromatic polyamides are generally known as aramides. The polymerization reaction of terephthaloyl chloride and phenylene diamine gives an aromatic amide called, Kevlar.
12. Which polyamide can be used as substitute of steel in belted radial tires?
a) kevlar
b) nomex
c) nylon 12
d) nylon 11
View Answer
Explanation: Kevlar provides a fibre material, than has strength equal to steel at one-fifth of its weight. So it is used as a substitute for the steel in belted radial tires and also in manufacturing of protective clothing.
13. Which of the following nylons has a lower specific gravity than the others?
a) nylon 6
b) nylon 66
c) both have nearly same
d) none of the mentioned
View Answer
Explanation: Nylon 6 and Nylon 66 have nearly same specific gravities which are close to 1.13 and 1.14, respectively.
14. How the viscosity of aromatic polyamide solutions does vary with the increase in volume fraction of polymer formed?
a) Increases always
b) first increases then decreases
c) first decreases then increases
d) decreases always
View Answer
Explanation: The aromatic polyamide solutions show an initial increase in the viscosity with increase in volume fraction of polymer followed by a reversal in the trend and an abrupt decrease in viscosity when a critical volume fraction of polymer is exceeded.
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