Chapter 15 Polymers Solutions
Question - 21 : - Discuss the main purpose of vulcanisation of rubber.
Answer - 21 : -
Natural rubber though useful has some problems associatedwith its use. These limitations are discussed below:
1. Natural rubber is quite soft and sticky at roomtemperature. At elevated temperatures (> 335 K), it becomes even softer. Atlow temperatures (< 283 K), it becomes brittle. Thus, to maintain itselasticity, natural rubber is generally used in the temperature range of 283K-335 K.
2. It has the capacity to absorb large amounts of water.
3. It has low tensile strength and low resistance toabrasion.
4. It is soluble in non-polar solvents.
5. It is easily attacked by oxidizing agents.
Vulcanization of natural rubber is done to improve uponall these properties. In this process, a mixture of raw rubber with sulphur andappropriate additive is heated at a temperature range between 373 K and 415 K.
Question - 22 : - What are the monomeric repeating units of Nylon-6 andNylon-6, 6?
Answer - 22 : - The monomeric repeatingunit of nylon 6 is
, which is derived from Caprolactam.
The monomeric repeating unit of nylon 6, 6 is
, which is derived fromhexamethylene diamine and adipic acid.
Question - 23 : - Write the names and structures of the monomers of thefollowing polymers:
(i) Buna-S (ii) Buna-N
(iii) Dacron (iv) Neoprene
Answer - 23 : -
| Polymer | Monomer | Structure of monomer |
| i | Buna-S | 1, 3-butadiene | 
|
| Styrene | 
|
| ii | Buna-N | 1, 3-butadiene |
|
| Acrylonitrile | 
|
| iii | Neoprene | Chloroprene | 
|
| iv | Dacron | Ethylene glycol | 
|
| Terephthalic acid | 
|
Question - 24 : - Identify the monomer in the following polymericstructures.
Answer - 24 : - (i)
(ii)
Answer
(i) The monomers of the given polymeric structure aredecanoic acid 
and hexamethylenediamine 
(ii) The monomers of the given polymeric structure are
How is dacron obtained from ethylene glycol andterephthalic acid?
Answer - 25 : -
The condensation polymerisation of ethylene glycol andterephthalic acid leads to the formation of dacron.
Question - 26 : - What is a biodegradable polymer? Give an example of abiodegradable aliphatic polyester.
Answer - 26 : -
A polymer that can be decomposed by bacteria is called abiodegradable polymer.
Poly-β-hydroxybutyrate-CO-β- hydroxyvalerate (PHBV) is abiodegradable aliphatic polyester.
