Q-5) Answer the following questions. (Any 3)
1) What is vulcanization?
2) What is meant by disaster management?
3) How much surface of earth is occupied by water and land respectively?
4) Why did the need for man-made materials arise?
Q-6) Give scientific reasons.
1) We must use cotton clothes in summer.
2) Coconut oil thinks in winter.
3) Humus is a natural material.
Q-7) Write the causes of the following. (Any 2)
1) Floods.
2) Storms. 3) Forest fires.
Answers
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Answer:
1- Vulcanization (British: Vulcanisation) refers to a range of processes for hardening rubbers.[1] The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice; however, it has also grown to include the hardening of other (synthetic) rubbers via various means. Examples include silicone rubber via room temperature vulcanizing and chloroprene rubber (neoprene) using metal oxides.Vulcanization can therefore be defined as the curing of elastomers; with the terms 'vulcanization' and 'curing' sometimes used interchangeably in this context. It works by forming cross-links between sections of polymer chain which results in increased rigidity and durability, as well as other changes in the mechanical and electrical properties of the material.[2] Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible.
The word vulcanization is derived from Vulcan, the Roman god of fire and forge.