This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Thermoplastics – 2”.
1. PMMA is otherwise known as _______
a) Polyacrylonitrile
b) Plexiglas
c) Polyvinyl fluoride
d) Perfluoroalkoxy ethylene
View Answer
Explanation: Polymethyl methacrylate (PMMA) is a commonly used acrylic material. It is also commonly known as Perspex or Plexiglas. They are hard, easily formed, and readily colored polymers. PMMA is produced by the process of addition polymerization.
2. What does the numbered suffix used in nylon polymers mean?
a) Molecular weight
b) Number of carbon atoms
c) Coefficient of thermal expansion
d) Number of monomer chains
View Answer
Explanation: Nylons, also known as polyamides, are polymers produced by a condensation reaction between an amine and an organic acid. The suffix indicates the number of carbon atoms, i.e. six carbon atoms in Nylon 6. A slash in the suffix denotes a copolymer, i.e. Nylon 6/12 is a copolymer of nylon 6 and nylon 12. Nylons are strong and abrasive resistant thermoplastics with good mechanical properties.
3. Acetals retain their properties up to ______
a) 50oC
b) 120oC
c) 240oC
d) 420oC
View Answer
Explanation: An acetal is a product of polymerization of formaldehyde. They have a low coefficient of friction, good strength, and can retain its properties up to 120oC. They are also known as polyacetal and polyoxymethylene.
4. Which of the following is an example of heterochain polymers?
a) Polyamide
b) Polycarbonate
c) Polyethylene
d) Polyacrylonitrile
View Answer
Explanation: Heterochain polymers are those which contain elements other than carbon in their molecular chain. A few examples of heterochain polymers are acetal, polycarbonate, and polyethylene terephthalate. Polycarbonates have good ductility, dimensional stability, and are transparent.
5. Polyethylene and polystyrene are examples of which kind of polymers?
a) Hydrocarbon plastics
b) Chlorocarbon polymers
c) Acrylic material
d) Polyamides
View Answer
Explanation: Hydrocarbon plastics are a kind of thermoplastic polymers made by polymerization of hydrocarbons. The common hydrocarbon plastics are polyethylene(PE), polypropylene (PP), and polystyrene (PS).
6. Which of the following are applications of polypropylene?
a) Buckets, bottle crates
b) CD cases, food boxes
c) Wire insulation, piping
d) Valves, fittings
View Answer
Explanation: Polypropylene is a high strength thermoplastic polymer which also has better stiffness than polyethylene. They are used for making buckets, battery cases, bottle and bottle caps etc. CD cases and food boxes are common applications of polystyrene. Wire insulation and piping are done using polyethylene.
7. Versalon, Zytel, and Plaskon are common trade names of which thermoplastic?
a) Acetal
b) Polycarbonate
c) Polyamide
d) Polyacrylonitrile
View Answer
Explanation: Polyamides are strong and abrasive resistant plastics which are used as fasteners, bushings, and electrical parts. Their common trade names are Nylon, Versalon, Ultramid, Zytel, and Plaskon. Acetal’s trade names are Delrin and Celcon, while that of polycarbonate are Lexan and Merlon.
8. Thermal resistance of polyimide is ______
a) 100oC
b) 250oC
c) 540oC
d) 760oC
View Answer
Explanation: Polyimide is a thermoplastic polymer which has good mechanical properties and a low coefficient of friction. It possesses excellent thermal resistance up to 250oC. They are used as bearings, seals, printed circuit boards, and fibers.
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