Plastic and rubber are both polymer materials, mainly composed of carbon and hydrogen atoms, and some contain a small amount of oxygen, nitrogen, chlorine, silicon, fluorine, sulfur and other atoms. They have special properties and uses. At room temperature, plastic is solid, very hard, and cannot be stretched or deformed. Rubber is not very hard, elastic, can be stretched and elongated, and can return to its original shape when the stretching stops. This is due to their different molecular structures. Another difference is that plastic can be recycled and reused many times, while rubber cannot be recycled directly. It can only be processed into recycled rubber before it can be used, so you can understand their close relationship when you see this. Rubber is widely used because of its characteristics. First of all,
① Thermal conductivity Rubber is a poor conductor of heat. Its thermal conductivity is about 2.2~6.28 W/m2·0K when the thickness is 25 mm. It is an excellent thermal insulation material. If the rubber is made into a microporous or sponge state, its thermal insulation effect will be further improved, and the thermal conductivity will drop to 0.4~2.0 W. Any rubber parts may generate heat due to hysteresis loss during use, so attention should be paid to heat dissipation.
② Thermal expansion Since there is a large free volume between rubber molecular chains, when the temperature rises, the internal rotation of its chain segments becomes easier, which will increase its volume. The linear expansion coefficient of rubber is about 20 times that of steel. This must be taken into account in the design of the vulcanization model of rubber products, because the linear size of the finished rubber product will be 1.2~3.5% smaller than the model. For the same type of rubber, the hardness and raw rubber content of the rubber compound also have a great influence on the shrinkage rate of the rubber compound. The shrinkage rate is inversely proportional to the hardness and directly proportional to the rubber content. The theoretical shrinkage rate of various rubbers is in the following order: fluororubber>silicone rubber>butyl rubber>nitrile rubber>chloroprene rubber>styrene-butadiene rubber>natural rubber, which is why rubber is chosen as the main raw material in the pipe fittings industry. At a time when the rubber industry is developing rapidly today, the sales of the world's rubber industry have exceeded US$250 billion, and rubber products have long become an important commodity in international trade. In the world market, rubber products have formed a product group centered on tires, focusing on industrial and construction products, and involving daily necessities such as rubber shoes and tapes, as well as various major categories such as medical care, culture and sports.