2.9.2 - Laboratory Activity : Characteristic of Vulcanised and Unvulcanised Rubber

Laboratory Activity 2.9.2: Characteristic of Vulcanised and Unvulcanised Rubber

Aim: To make vulcanised rubber and to compare vulcanised and unvulcanised rubber.
Problem statement: What is the difference between vulcanised and unvulcanised rubber in term of elasticity?
Hypothesis: Vulcanised rubber is more elastic than unvulcanised rubber.
Variable:

	»	Fixed variable : The width and thickness of rubber strip, mass of weight
	»	Manipulated variable : Type of rubber strips
	»	Responding variable : Elasticity

Material: » Latex » Ethanoic acid » Sulphur monochloride solution in methylbenzene

Apparatus: » White tile » Knife » Glass rod » Beaker » Retort stand » Weight » Ruler

Procedure:

	►	(A) Preparation of vulcanised rubber 1. 2. 25cm3 of latex is poured into the beaker and few drops of ethanoic acid is added. 3. The mixture is stirred and quickly poured into the white tile. 4. A glass rod is used to spread out the latex to get a 1 mm thick layer of latex. 5. The latex is left to coagulate. 6. The rubber sheet formed is then cut into two strips of the same size. 7. One of the strips is dipped into the sulphur monochloride solution for 2 minutes.
	►	(B) Comparing vulcanised and unvulcanised rubber 1. 2. The unvulcanised rubber strip is hung vertically using a clip and retort stand as shown in the diagram. 3. The length of unvulcanised rubber is measured. 4. A weight of 25g is hung on the rubber strip and the length of the unvulcanised rubber strip is recorded. 5. The weight is released, and the length of the rubber strip is measured again. 6. The experiment is repeated by using the vulcanised rubber strip.

Obervation:

►

Extension of rubber strip Type of rubber strip Original length (cm) Length with weight (cm) Extension (cm) Length after weight is removed (cm) Unvulcanised rubber 6 9.5 3.5 9 Vulcanised rubber 6 8 2 8

Discussion:

	►	The unvulcanised rubber strip extends more as compared to the vulcanised rubber strip.
	►	Vulcanised rubber has a greater resistance to force (weight)
	►	The vulcanised rubber strip has an ability to return to its original length after the weight is taken off. Thus, the vulcanised rubber strip is more elastic.

Conclusion:

►

Vulcanised rubber is more elastic as compared with natural rubber.

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