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Answer -
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.