Question

Natural rubber obtained from rubber latex is soft and sticky.

a) Suggest a method to improve the stiffness of rubber.

b) Explain the above method.

c) Classify the following into natural and synthetic polymers:
Nylon, Starch, Cellulose, PVC

Answer 1

a) Vulcanisation

b) It is the process of heating a mixture of raw rub- ber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross-links at the reactive sites of double bonds in the polyisoprene chain and thus rubber gets stiffened. Vulcanisation improves the physical properties of natural rubber-like elasticity, water absorption capacity and solubility. It also increases its resistance to attack by oxidising agents.

c) Natural polymers – Cellulose, Starch Synthetic polymers – Nylon, PVC