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The most essential difference between plastic and rubber is plastic deformation when the plastic deforms, and the rubber is elastically deformed. In other words, it is not easy to restore the original state after the plastic is deformed, and the rubber is relatively easy. The elasticity of the plastic is very small, usually less than 100%, and the rubber can reach 1000% or more. The molding process is completed after the molding process is completed, and the vulcanization process is required after the rubber molding process is completed.
Plastic and rubber belong to the same polymer material, mainly composed of carbon and hydrogen atoms, and some contain a small amount of oxygen, nitrogen, chlorine, silicon, fluorine, sulfur and other atoms. Their properties are special and their use is special. At normal temperature, The plastic is solid, very hard, and can not be stretched and deformed. The hardness of the rubber is not high, it is elastic, it can be stretched and lengthened, and the stretching can be restored to its original state. This is due to the difference in their molecular structure. Another difference Plastics can be recycled and reused many times, while rubber can not be recycled directly. It can only be processed into reclaimed rubber before it can be used. The plastic is in the form of 100 to 200 degrees and the rubber is 60 to 100 degrees. The shape is similar. Plastic does not include rubber.
Complex said:
Broadly speaking, rubber is actually a kind of plastic, and plastics include rubber. Now detailed
First, the formation of raw rubber:
Raw rubber can be divided into two categories: natural rubber and synthetic rubber:
1. Natural rubber: The raw rubber material is formed by cutting the mouth of the rubber trunk, collecting the glue flowing out, and removing the impurities, solidification, smoking, drying and the like.
2. Synthetic rubber: By-products produced by the petrochemical industry, according to different needs, synthetic raw materials of different physical properties. Commonly used are: SBR, NBR, EPDM, BR, IIR, CR, Q, FKM, etc. However, due to the difference in the synthesis method, the same type of rubber can be divided into several different raw rubbers, and through the formulation of the formula, any type of rubber can be changed into thousands of raw rubber materials that meet the requirements of the products.
Natural rubber comes from tropical and subtropical rubber trees. Because rubber plays an important role in the industrial, agricultural, and defense fields, it is an important strategic material, which has led countries that lack rubber resources to take the lead in research and development of synthetic rubber.
Second, the chemical composition of rubber
By analyzing the chemical composition of natural rubber, it was found that its basic composition is isoprene. Then inspired people to use isoprene as a monomer for polymerization, a synthetic rubber, called isoprene rubber. The structure and properties of isoprene rubber are basically the same as those of natural rubber. Since isoprene was only available from turpentine at the time, the source of raw materials was limited, and butadiene was abundant, a series of synthetic rubbers were developed based on butadiene. Such as butadiene rubber, styrene butadiene rubber, nitrile rubber and neoprene.
With the development of the petrochemical industry, various gases such as ethylene, propylene, butylene, isobutylene, butane, pentene and isoamylene can be obtained from high temperature cracking and separation and purification of oil gas and refinery gas. A good raw material for synthetic rubber.
Of the world's rubber production, natural rubber accounts for only about 15%, and the rest are synthetic rubber. There are many varieties of synthetic rubber with different properties, which can replace or even exceed natural rubber in many occasions. Synthetic rubber can be divided into general rubber and special rubber. General purpose rubber is used in a large amount, for example, styrene-butadiene rubber accounts for 60% of synthetic rubber production; secondly, butadiene rubber, which accounts for 15%; in addition, isoprene rubber, neoprene rubber, butadiene rubber, ethylene propylene rubber, butyl rubber Etc., they are all general purpose rubber.
Third, the preparation of rubber raw materials:
The preparation of rubber raw materials can be divided into three basic processes:
1. Mastication: Plasticizing is to cut the raw rubber, and plasticize and homogenize the raw rubber to help the mixing operation of the compounding agent. The effect is to improve the dispersion of the drug, prevent the frictional heat generated in the operation, and cause the rubber to burn, thereby changing the processability of the rubber.
2. Mixing: Mixing is to mix the mixed drugs into the raw rubber which is finished by mastication, and the quality of the mixing directly affects the quality of the products. The drug is unevenly dispersed, the molecular structure cannot be completely crosslinked, and the rubber cannot achieve the desired physical properties.
3. Extrusion: the raw rubber that has been kneaded, after the extrusion operation, presses out the excess air contained in the rubber compound and completes the required thickness to facilitate the molding work in the mold.
Fourth, the molding of rubber:
The molecular structure of raw rubber is an elastomer with unsaturated long bonds. Therefore, proper molding additives and external environmental factors (such as time, temperature, pressure, etc.) must be formed in the molding requirements, and the unsaturated bonds should be destroyed. The combination is a saturated bond, and with vacuum assist, the contained air is completely forced out. In this way, the molded rubber can be used to its intended characteristics. If there are any defects in the molding process (such as formula error, insufficient time, temperature mismatch, etc.), it can cause loss of physical properties, release of excess drugs, deformation, accelerated aging, and serious adverse phenomena.
Fifth, the aging phenomenon of rubber:
Depending on the environmental conditions in which the finished rubber product is located, it may cause cracking or hardening, and deterioration of rubber physical properties over time, which is called aging. Causes of aging, external factors and internal factors:
1. External factors: external factors such as aerobic, oxide, ozone, heat, light, radiation, mechanical fatigue, lack of processing, etc.