Rubbers are usually selected for oil-resistance applications on the basis of their properties before and after aging in test fluids under conditions that are related to service environment and the cost and ease of processing of their compounds. All of the oil-resistance rubbers are special rubbers such as nitrile rubber(NBR), chloroprene rubber(CR), polysulphide rubber(TR) and so on. There are no obvious general trends toward the use of other single rubber (i.e. general purpose rubber) in recent or predicted usage. This is because of the wide variety of properties required in industrial applications, the large number of specifications for each types of industries, and the versatility of special rubbers. The successful development and use of oil-resistant synthetic rubbers has inevitably led to a slackening of interest in oil-resisting natural rubber. However, since Thailand is a natural rubber-producing country and a large volume of oil-resistant synthetic rubber has to be imported every year and is relatively expensive. This gives some importance to the problem of compounding natural rubber so as to confer the best resistance to the swelling action of fuels and petroleum hydrocarbons.
