Plastic and rubber is the most essential difference between plastic deformation occurs when the plastic deformation, and rubber is elastic deformation. In other words, the plastic deformation is not easy to restore the original state, and the rubber is relatively much easier. The elasticity of plastics is very small, usually less than 100%, while the rubber can reach 1000% or more. Plastics in the forming process of the vast majority of the molding process is completed, and the rubber forming process after the need to be vulcanized process.
Plastic and rubber are high molecular material, mainly composed of two kinds of carbon and hydrogen atoms, and some contain a small amount of oxygen, nitrogen, chlorine, fluorine, silicon, sulfur atoms, its special properties, use is also special. At room temperature, the plastic is not solid, hard, and tensile deformation of rubber hardness is not high., elastic, can be stretched, and stop pulling back to normal. This is due to differences in their molecular structure. Another difference is the plastic can be repeatedly recycled, while the rubber cannot be directly recycled, can only be processed and then reclaimed rubber, plastic and rubber. Available in the form of more than and 100 to 200 degrees at 60 to 100 degrees. The morphological similarity does not include plastic rubber.
In a broad sense, the rubber is actually one kind of plastic, the plastic includes the rubber. Is detailed introduction of the
The formation of a rubber:
Rubber can be divided into natural rubber and synthetic rubber in two categories:
1: natural rubber from rubber tree cutting mouth, collect the glue outflow, after removing impurities, solidification, smoke, drying process, raw material and the formation of.
2 synthetic rubber by-products produced by the petrochemical industry, according to the different needs of different raw material synthesis. Commonly used for such as: NBR, SBR, EPDM, BR, IIR, CR, Q, FKM, etc.. But because of the difference in synthetic way, similar material can be divided into several different types of rubber, and through the formula set, any type of plastic material, can change into raw material accords with the demand for thousands of products.
Natural rubber from tropical and subtropical rubber trees. Because rubber plays an important role in industry, agriculture and national defense, it is an important strategic material, which promotes the development of synthetic rubber in the country with the lack of rubber resources.
Two, rubber chemical composition
Through the analysis of the chemical composition of natural rubber, it is found that the basic composition is. So inspire people to use the polymerization of the monomer as a monomer polymerization, the synthesis of rubber, known as iso. The structure and properties of ISO e rubber are basically the same as natural rubber. At that time only isoprene from turpentine, limited sources of raw materials, and butadiene rich sources, so to develop a series of butadiene based synthetic rubber. Such as polybutadiene rubber, styrene butadiene rubber, nitrile rubber and chloroprene rubber etc..
With the development of petroleum chemical industry, from the oil field gas and refinery gas by pyrolysis and purification, can obtain ethylene and propylene, butene and butane, isobutene, pentene, isoprene and other gases, which is a good material for the manufacture of synthetic rubber.
Rubber production in the world, natural rubber accounted for only about 15%, and the rest are synthetic rubber. Synthetic rubber varieties are many, the performance of different, in many occasions can be replaced, or even more than natural rubber. Synthetic rubber can be divided into general and special rubber. General large amount of rubber, such as styrene butadiene rubber synthetic rubber production accounted for 60%; followed by butadiene rubber, accounted for 15%; in addition, isoamyl rubber, chloroprene rubber, nitrile, ethylene propylene rubber, butyl rubber and so on, they all belong to the general rubber.
Three, the preparation of rubber raw materials:
The preparation of rubber raw materials can be divided into three basic processes:
1: Plastic plastication practice is gum cut, and rubber can be plasticized, homogenization, help a complexing agent mixing operation. The effect is to improve the dispersion of drugs, to prevent the friction heat generated in operation, and the rubber scorch phenomenon occurs, and then change the processing of rubber.
2 Mixing: mixing with drug is uniformly mixed in the finished rubber plastication, and mixing quality, directly affect the products of good or not. Drug dispersion is uneven, the molecular structure can not be completely cross-linked, rubber is not able to achieve the desired physical properties.
3 out: complete mixing of raw rubber, after extrusion operation, the excess air pressure containing compound, and complete the required thickness, in order to facilitate the mold operation.
Four, rubber molding:
The molecular structure of rubber elastic unsaturated bond length, so forming elements, with appropriate chemical additives and external environmental factors (such as time, temperature, pressure, etc.), the unsaturated bond failure, re combination of saturated bonds, and vacuum assisted, the air force will be included. So, it can make the rubber molding, play its due characteristics. If there is any deficiency in its molding process (such as formulation errors, lack of time, temperature, improper) can cause property loss, excess drug release, deformation, accelerated aging, resulting in various serious adverse phenomenon.
Five, rubber aging phenomenon:
The rubber products according to environmental conditions, with the lapse of time, caused by cracking or hardening, rubber material degradation, called aging. Causes of aging, there are external factors and internal factors:
1 external factors: external factors such as oxygen, oxide, ozone, heat, light, radiation, mechanical fatigue, lack of processing process, etc..
2 internal factors: internal factors are the types of rubber, molding method, the degree of bonding, with the types of drugs, processing engineering factors, etc..
Prevention of aging,
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