This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Types of Rubbers”.
1. What is the trade name for natural polyisoprene?
a) Natural rubber
d) Buna acrylonitrile
Explanation: Natural rubber is a common material consisting of isoprene combined with impurities and water. Natural rubber is also known as India rubber and belongs to natural polyisoprene chemical group.
2. What is the percentage of elongation of styrene butadiene?
Explanation: Styrene butadiene refers to a high abrasion resistant rubber composed of styrene and butadiene. These rubbers go by the common name of Buna S or SBR (styrene butadiene rubber). The percentage of elongation of SBR is 450-500%.
3. What is Buna N rubber?
d) Acrylonitrile butadiene
Explanation: Buna N is a synthetic rubber composed of acrylonitrile and butadiene. It is also commonly known as NBR, Krynac, or Europrene. This rubber is used in O-rings and hoses.
4. What is the service temperature of polysiloxane?
a) -50 to 150
b) -50 to 105
c) -60 to 120
d) -90 to 250
Explanation: Polysiloxane, otherwise known as silicone (SIL) is a rubber used for its temperature insulation properties. It has a 600% elongation and is most useful around a temperature range of -90oC to 250oC.
5. What is the hardening temperature of unvulcanized natural rubber?
Explanation: Unvulcanized natural rubber is a tough and elastic material which softens of heating. It becomes tacky at 30oC and hardens at around 5oC. This rubber oxidizes to a sticky mass when out in the sun.
6. Which of the following is not a characteristic of natural rubber?
b) High strength
c) High hysteresis
d) Abrasion and tear resistant
Explanation: Natural rubber is processed from a liquid known as rubber latex. It has high strength and possesses good tear and abrasion resistance. However, it is easily attacked by solvents and gasoline, and also possesses low hysteresis.
7. Addition of ______ results in the vulcanization of rubber.
c) Carbon monoxide
d) Particulate matter
Explanation: Vulcanization is a process which increases the strength of natural rubber. It is carried out by heating a mixture of raw rubber and sulfur. The vulcanized rubber is commonly used in the manufacture of tires.
8. __________ is a reinforcement filler.
a) Carbon black
c) Barium sulfate
Explanation: Fillers can be classified as either reinforcing fillers or inactive fillers. Carbon black and synthetic white fibers based on silica and alumina are examples of reinforcing fillers. Talc, barium sulfate, chalk, and chinaclay are examples or inactive fillers.
9. Buna S rubbers consisting of over 50% styrene are considered as _________
Explanation: Buna S (SBR) rubbers differ and quality and grades with respect to the amount of styrene and butadiene. Low-temperature resistant rubber may only contain 9% styrene whereas 44% styrene has good flow characteristics. When the amount of styrene exceeds 50%, it is considered plastic.
10. What is ACM elastomer?
a) Isobutylene Isoprene
b) Ethylene propylene
Explanation: Polyacrylate elastomers, also known as acrylics, are composed of polymers of butyl or ethyl acrylate. These elastomers are used for special purposes with a low-volume usage, such as parts involving oil.
11. What is the glass transition temperature of polybutadiene?
a) -100 F
b) -25 F
c) 125 F
d) 300 F
Explanation: Polybutadiene elastomers are known for their low-temperature performance. They have the lowest brittle or glass transition temperature after silicones. These elastomers possess excellent resilience and abrasion resistance.
12. What is Hypalon?
c) Chlorosulfonyl polyethylene
d) Isobutylene Isoprene
Explanation: Chlorosulfonyl polyethylene is a special elastomer used in a combination with another elastomer or by itself. It is otherwise known as Hypalon or CSM. A polysulphide elastomer is otherwise known as Thiokol.
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