This set of Polymer Engineering Questions and Answers for Experienced people focuses on “Identification of Common Plastics and Rubbers-2”.
1. What colour change is observed when few drops of alcoholic NaOH is added to polyvinyl chloride solution?
a) colourless to red
b) colourless to yellow
c) colourless to blue
d) colourless to grey
Explanation: When few drops of alcoholic NaOH is added to the solution of polyvinyl chloride then the mixture changes from colourless to yellow, yellow-brown, dark-brown to black with time.
2. Which polymer gives dark brown precipitate when its pyridine solution is heated in the presence of alcoholic NaOH solution?
a) polyvinylidene chloride
b) polyvinyl chloride
c) polyvinyl alcohol
d) all of the mentioned
Explanation: When pyridine solution of polyvinyl chloride is heated in the presence of few drops of alcoholic NaOH solution, eventually dark brown precipitate is obtained.
3. What colour is developed when polyvinylidene chloride is immersed in morpholine?
a) dark blue
b) light yellow
4. A small volume of iodine solution when added to acidic solution of polymer X produced a blue colour immediately. An addition of pinch of borax resulted the same. Which of the following could be X?
a) polyvinyl acetate
b) polyvinyl alcohol
c) polyvinyl chloride
d) polyvinylidene chloride
Explanation: Polyvinyl alcohol when treated with iodine solution develops blue colour solution.
5. What colour is obtained when polyvinyl acetate is brought in contact with iodine solution?
Explanation: Polyvinyl acetate when brought in contact with dilute iodine solution gives deep brown colour.
6. A sample of polystyrene is warmed under reflux in concentrated nitric acid and the clear mixture is poured in water to yield a X coloured precipitate. This precipitate is then extracted with ether and then with NaOH solution followed by washing with water in each extraction. The nitro compounds from the combined final aqueous extract and alkaline extract using concentrated HCl and zinc. The final solution after being diazotized and then cooled is poured into excess of alkaline naphthol to give Y coloured solution. What are the colours X and Y?
a) pale yellow and deep red
b) deep blue and deep brown
c) deep red and light pink
d) light yellow and brown
Explanation: When polystyrene is paased through this test, initially pale yellow colour is formed and then finally a deep red colour solution is formed.
7. Which of the following polymer does not produce yellow flame on heating?
a) phenol-formaldehyde resin
d) nitrile rubber
Explanation: Nylons produce blue flame with a yellow tip on heating.
8. A polymer X produces a pale yellow flame with light blue-green edge on heating. It produces a fish like odour and is alkaline in nature. Which of the following polymer represents X?
a) phenol formaldehyde resin
b) melamine formaldehyde resin
d) butyl rubber
Explanation: Melamine formaldehyde resin produces a similar flame and produces a fish like smell on heating.
9. Which of the following polymer produces camphor like odour on heating?
a) ethyl cellulose
b) cellulose nitrate
d) cellulose acetate
Explanation: Cellulose nitrate produces camphor like smell as it is plasticized with camphor.
10. Which of the following polymers does not produce a smoky flame?
a) polybutadiene rubber
b) gutta percha
c) poly (vinyl acetate)
d) polysulphide rubber
Explanation: Polysulphide rubbers produce a bluish, smoke free flame while the rest other rubbers produce smoky flame.
11. Which of the following polymers do not produce black residue on heating?
a) chlorinated rubber
b) poly (vinyl alcohol)
c) poly (vinyl chloride)
d) none of the mentioned
Explanation: All the polymers mentioned, i.e. chlorinated rubber, poly vinyl alcohol and poly vinyl chloride produce black residue on heating.
12. Which of the following polymer produces an odour resembling burning paraffin wax on heating?
d) butyl rubber
Explanation: Polyethylene produces a smell like burning paraffin wax on heating.
13. Polymers of type A produce yellow smoky flame on heating with an unpleasant and sweet smell. They also melt or char giving acidic distillate and black residue.
Which of the following could be A?
d) ethyl cellulose
Explanation: Polyesters produce yellow smoky flame with unpleasant and sweet smell on heating. It chars giving acidic distillate and black residue.
14. What is the colour of flame when chlorinated rubber is heated?
b) blue green
d) yellow green
Explanation: Chlorinated rubber produces a yellow green flame with strongly acidic fumes on heating.
15. Which of the following polymer continues to burn even on the removal from flame?
a) chlorinated rubber
b) poly vinyl chloride
c) butyl rubber
Explanation: Butyl rubber continues to burn even on the removal from flame while the rest other polymers burns but self extinguishes on removal from flame.
Sanfoundry Global Education & Learning Series – Polymer Engineering.
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