This set of Polymer Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Synthetic Rubber”.
1. Which synthetic rubber is also commonly known as hypalon?
a) polychloroprene rubber
b) chloro-sulphonated polyethylene
c) styrene-butadiene rubber
d) nitrile rubber
Explanation: Chlorosulphonated polyethylene (CSP) is commonly known in the trade as Hypalon.
2. What kind of synthetic rubbers are commonly known as thiokols?
a) polyurethane rubbers
b) polysulphide rubbers
c) fluorocarbon rubbers
d) polyacrylic rubbers
Explanation: Polysulphide rubbers are commonly known as Thiokols due to the presence of thio group in their structure.
3. What is the cis content of polybutadiene rubber obtained by emulsion polymerization using redox catalyst?
d) None of the mentioned
Explanation: Polybutadiene prepared by emulsion polymerization in the presence of redox catalysts is lower in cis content i.e. below 10%.
4. Which of the following catalyst is used to obtain polybutadiene of cis content <40%?
a) coordination catalyst based on Ni, Co
b) redox catalyst
c) zeiglar natta catalyst
d) butyl lithium catalyst
Explanation: When polybutadiene is prepared using butyl lithium catalyst, rubber of lower cis content (<40%) is formed. Using coordination catalyst, high cis content (>90%) polybutadiene is obtained.
5. Which synthetic rubbers are blended with BR to make its extensive use in tyres?
a) NR and SBR
b) NBR and SBR
c) NR and NBR
d) NR, NBR and SBR
Explanation: BR is blended with natural rubber and SBR in the manufacture of tyres for improved milling, wet skid resistance, while BR imparts excellent abrasion resistance to car and truck tyres.
6. Consider the following statements about emulsion SBR and solution SBR.
I. Solution SBR has higher content of non-rubber materials than emulsion SBR
II. Solution SBR has higher molecular weight but broader molecular weight distribution than emulsion SBR
III. Solution SBR has higher cis-1,4-polybutadiene content than emulsion SBR
Which of the following statements are true?
a) I, II, III
b) I, II
c) III only
d) I only
Explanation: Solution SBR has a lower content (nearly 2%) of non-rubber materials while emulsion SBR has non-rubber materials in excess of 10%. Solution SBR has narrower molecular weight distribution, higher cis-1,4-polybutadiene content and higher molecular weight than emulsion rubber.
7. What are the temperature conditions for production of hot emulsion SBR and cold emulsion SBR, respectively?
a) 50-60 ᵒC and 5 ᵒC
b) 80-90 ᵒC and 5 ᵒC
c) 50-60 ᵒC and 10 ᵒC
d) 80-90 ᵒC and 10 ᵒC
Explanation: Polymerization of butadiene and styrene carried out at 50-60 ᵒC gives hot emulsion SBR and when it is carried out at 5 ᵒC using appropriate redox initiators gives a product known as cold emulsion SBR.
8. Which configuration of butadiene units is present in highest amount in SBR at 50 ᵒC?
d) all of the mentioned
Explanation: The butadiene units in SBR are composed of approximately 15-20% of cis-1,4; 60-70% of trans-1,4; and 15-20% of 1,2 configuration for the polymer. The rubbers produced at low temperatures generally have higher content of trans-1,4 butadiene units.
9. What is the correct order of the poor resilience characteristics in the given rubbers?
Explanation: Butadiene rubbers have high resilience characteristics than natural rubber while SBR have poor resilience characteristics as compared to natural rubber. Therefore, the order follows BR>NR>SBR.
10. What is the IUPAC name of the monomer of polychloroprene?
d) none of the mentioned
Explanation: The monomer of Polychloroprene is chloroprene whose IUPAC name is 2-chloro-1,3-butadiene.
11. Which type polymerization is used to produce Polychloroprene commercially?
a) solution polymerization
b) bulk polymerization
c) emulsion polymerization
d) all of the mentioned
Explanation: polychloroprene is produced commercially by emulsion polymerization using soap such as rosin soap.
12. Which material is made to react with polymer latex of polychloroprene to set a desired plasticity when modification with sulphur is done?
a) tricresyl phosphate
b) triethylthiuram sulphide
c) tetraethylthiuram sulphide
d) dioctyl phthalate
Explanation: Certain grades of polymer are modified using sulphur as a crosslinkin-agent where the latex, after completion of polymerization, is allowed to stand and react with tetraethylthiuram sulphide to restore desired plasticity of the polymer.
13. Which of the following feature is responsible for the crystallizable nature of neoprene?
a) 1,4-trans structure
b) 1,4-cis structure
c) all of the mentioned
d) none of the mentioned
Explanation: Neoprene has an overwhelmingly 1,4-trans structure and this structural feature is responsible for its crystallizable nature.
14. What is the average curing mixture for the vulcanization of Polychloroprene rubber (CR)?
a) 5 parts ZnO and 4 parts MgO per 100 parts of neoprene
b) 4 parts ZnO and 5 parts MgO per 100 parts of neoprene
c) 8 parts sulphur per 100 parts of neoprene
d) 10 parts sulphur per 100 parts of sulphur
Explanation: Vulcanization of CR is more conveniently accomplished with zinc oxide and magnesium oxide rather than using sulphur or sulphur donor compounds. 5 parts ZnO and 4 parts MgO per 100 parts of neoprene are used as the average curing mixture.
15. Most filled technical Cr compounds show better resilience than NR of similar loading. State true or false.
Explanation: With increasing filler loading in NR and CR compounds, however, the resilence drops, though to a lesser content for CR system. This is why, most filled CR compounds show better resilence than NR of similar loading.
Sanfoundry Global Education & Learning Series – Polymer Engineering.
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