1. Which of the following resistances is provided by the presence of chlorine in CR molecules?
a) resistance to flex cracking
b) ozone resistance
c) flame resistance
d) resistance to oxidative aging
Explanation:CR compounds exhibit some inherent flame resistance due to the presence of chlorine in the molecules.
2. Which one of the following conditions does not resemble to hot nitrile rubbers?
a) high temperature 25-50 C
b) high gel content
c) little gel content
d) branched units
Explanation:Hot nitrile rubbers are formed by copolymerization at around 25-50 C which have characteristic toughness due to the presence of gels and branch units in polymer chains.
3. Which property of NBR-PVC blends mends its way to be used in footwear soling?
a) good weathering resistance
b) good abrasion resistance
c) good flame resistance
d) solvent resistance
Explanation: Good abrasion resistance had led to the use of NBR-PVC blends in footwear soling
4. What is the polymerization temperature of isobutylene to give high molecular weight polyisobutylene?
a) 80 C
b) -80 C
c) 25 C
d) -25 C
Explanation:Isobutylene can be commercially polymerizaed to high molecular weight polyisobutylene using cationic catalysts such as boron trifluoride at a temperature of -80 C.
5. What is the monomer composition of IIR polymer or Butyl Rubber?
a) isobutylene
b) isoprene
c) isoprene and isobutylene
d) isoprene, isobutylene and chloroprene
Explanation:Butyl rubber or isobutylene-isoprene rubber (IIR) is formed by the copolymerization of isoprene and isobutylene monomers.
6. Which of the following properties does not correspond to butyl rubbers?
a) poor resilience
b) low heat build-up
c) high internal viscosity
d) good flexibility even below -40 C
Explanation:Butyl rubber retains its flexibility even below -40 C by not crystallizing at lower temperatures. The methyl side groups of butyl rubber hinder elastic movements, thus giving rise to high internal viscosity and consequently, high heat build-up and poor resilience.
7. Butyl Rubber usually exhibits high gas permeability. State true or false.
a) True
b) False
Explanation: The densely packed structure of the linear hydrocarbon chains makes butyl rubber exhibit unusually low gas permeability.
8. Polyisobutylene rubbers can be vulcanized easily using conventional curing systems. State true or false.
a) true
b) false
Explanation: Polyisobutylene is rubbery in nature but it cannot be vulcanized easily using conventional curing systems because of the absence of unsaturation in the chain molecules.
9. Which of the following is used for vulcanization of butyl rubber to produce vulcanizates with improved heat resistance and aging characteristics?
a) sulphur
b) oxime and red lead
c) phenol-formaldehyde resins
d) carbon black
Explanation:Vulcanization with phenol-formaldehyde resins produces the vulcanizates with improved heat resistance and aging characteristics as compared to other vulcanizing agents.
10. How can the curing of halobutyl rubbers be done conveniently?
a) sulphur cure
b) amine cure
c) quininoid cure
d) all of the mentioned
Explanation: Curing of chlorobutyl or bromobutyl rubbers can be conveniently done following conventional sulphur cure or quininoid cure, resin cure, amine cure or simply metal oxide cure.