This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Insulating Materials – 2”.
1. A copolymer of butadiene and acrylonitrile is known as __________
a) Nitrile rubber
b) Butyl rubber
c) Polysulphide rubber
d) Fluorine rubber
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Explanation: Nitrile rubber is a copolymer formed by a combination of butadiene and acrylonitrile. It has good tensile strength and exceptional adhesion. It is largely used in aircraft fuel tanks, printing rollers, and O-rings.
2. What is the percentage of elongation of styrene butadiene rubber?
a) 60-70%
b) 140-160%
c) 250-300%
d) 500-600%
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Explanation: Styrene butadiene rubber is a low-cost synthetic rubber having tremendous resistance to aging. It has a poorer tensile strength which can be improved by vulcanizing, and elongation of 500-600%.
3. Isoprene added to isobutylene gives _______
a) Nitrile rubber
b) Butyl rubber
c) Polychloroprene rubber
d) Silicone rubber
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Explanation: Butyl rubber is a polymer made from a combination of isobutylene and 3% of isoprene. It possesses low strength and high elongation, with good chemical and dielectric properties. It is mainly used for liners and inner tubes.
4. What is the common name for polysulphide rubber?
a) Neoprene
b) Polyurethane
c) Thiokol
d) Hypalon
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Explanation: Thiokol is a rubber which holds admirable resistance to oil and solvents. It also has good electrical resistivity and superb resistance to ozone. It is mainly used in aircraft fuel tanks, gaskets et cetera.
5. Which of the following is not a method of fabrication of rubber?
a) Compression molding
b) Calendering
c) Buffing
d) Vacuum forming
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Explanation: Some of the basic forming and fabrication techniques for rubber include compression molding, calendering, injection and transfer molding, and extrusion among others. Tumbling, trimming, and buffing are techniques of finishing this fabricated rubber.
6. Mica manufactured by internal resistance melting method is melted at ______
a) 1118oC
b) 1208oC
c) 1365oC
d) 1480oC
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Explanation: Mica is usually manufactured either as ruby mica or phlogopite mica. The synthetic mica is produced by internal resistance melting method. This method uses graphite electrodes and melts mica at 1365oC.
7. Ruby mica is more commonly known as ______
a) Muscovite
b) Phlogopite
c) Urethane
d) Neoprene
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Explanation: Natural mica is available as muscovite and phlogopite among the commonly used forms. Muscovite, otherwise known as ruby mica, is generally odorless. It is often favored in electrical applications.
8. Natural muscovite is normally stable up to ______
a) 300oC
b) 600oC
c) 800oC
d) 1000oC
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Explanation: Muscovite contains about 4.5% water and is stable up to 600oC. Above this temperature, it breaks down due to volatilization. Phlogopite contains 3% water and is stable up to 800oC.
9. Which of the following is not a form of mica?
a) Fully trimmed
b) Partially trimmed
c) Film
d) Wire
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Explanation: Mica is commonly available in four forms classified as fully-trimmed, partially-trimmed, films, or scrap. Fully-trimmed and partially-trimmed mica are of a minimum of 0.007 inches in thickness. This quality of mica influences the cost of the material.
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