simply put:
The most essential difference between plastic and rubber is plastic deformation when the plastic deforms, and rubber is elastic deformation. In other words, the plastic is not easily restored to its original state after deformation, and rubber is relatively much easier. The elasticity of plastic is very small, usually less than 100%, while rubber can reach 1000% or more. In the molding process, most of the molding process is finished and the product process is completed; after the rubber molding process, the vulcanization process is required.
Plastic and rubber belong to the same high-molecular materials, mainly composed of carbon and hydrogen atoms, and some contain a small amount of oxygen, nitrogen, chlorine, silicon, fluorine, sulfur and other atoms, its special performance, use is also special. At room temperature, Plastics are solid, hard, and cannot be stretched and deformed. Rubber hardness is not high, elastic, stretchable, and stretching can be reversed. This is due to differences in their molecular structure. Another difference It is plastic that can be reused repeatedly for recycling, while rubber can not be recycled directly and can only be processed into reclaimed rubber before it is available. The plastic is in the range of 100 degrees to 200 degrees and rubber is between 60 and 100 degrees. Similar in shape. Plastic does not include rubber.
Complex say:
Broadly speaking, rubber is actually a kind of plastic, and plastic includes rubber. Detailed introduction
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 is formed by cutting the rubber trunk and collecting the glue that flows out, and then goes through impurities, solidification, smoke, and drying processes.
2. Synthetic rubber: By-products produced by the petrochemical industry, according to different needs, synthetic raw materials with different properties. Commonly used such as: SBR, NBR, EPDM, BR, IIR, CR, Q, FKM and so on. However, due to the differences in the synthesis methods, different types of raw rubber can be separated from the same type of rubber, 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 products.
Natural rubber comes from tropical and subtropical rubber trees. As rubber plays an important role in the fields of industry, agriculture and national defense, it is an important strategic material, which has led countries that lack rubber resources to take the lead in researching and developing 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. Inspired people to use isoprene as a monomer for polymerization, resulting in a synthetic rubber called isoprene rubber. Isoprene rubber basically has the same structure and properties as natural rubber. Since isoprene was available only from turpentine oil at the time, the source of raw materials was limited, and butadiene was abundant in origin, so a series of synthetic rubbers was developed based on butadiene. Such as butadiene rubber, styrene butadiene rubber, nitrile rubber and neoprene and so on.
With the development of the petrochemical industry, various gases such as ethylene, propylene, butylene, isobutylene, butane, pentene, isoprene, etc. can be obtained from the oil field gas and refinery gas after high-temperature cracking and separation and purification. Good raw material for synthetic rubber.
In the world rubber production, natural rubber accounts for only about 15%, and the rest is synthetic rubber. Synthetic rubber has a wide variety of different properties and can replace or even exceed natural rubber in many applications. Synthetic rubber can be divided into general rubber and special rubber. A large amount of general rubber, such as styrene-butadiene rubber accounts for 60% of the output of synthetic rubber; followed by butadiene rubber, accounting for 15%; in addition there is isoprene rubber, neoprene rubber, Buna rubber, ethylene propylene rubber, butyl rubber And so on, they are universal rubber.
Third, the preparation of rubber raw materials:
The preparation of rubber raw materials can be divided into three basic processes:
1. Plastic smelting: Plastic sculpting is to cut the raw rubber and plasticize and homogenize the raw rubber to help the mixing agent's kneading operation. The effect is to improve the dispersion of medicines, prevent the generation of frictional heat during operation, and cause scorch of rubber, which in turn changes the processability of the rubber.
2. Mixing: Mixing is blending the drug into the raw rubber that is plasticized, and the quality of mixing directly affects the quality of the product. Uneven dispersion of the drug, molecular structure can not be fully crosslinked, rubber can not achieve the desired physical properties.
3. Extrusion: Raw rubber that has been kneaded is pressed out to press out the excess air contained in the rubber and complete the required thickness to facilitate molding operations in the mold.
Fourth, rubber molding:
The raw rubber molecular structure is an unsaturated long bond elastomer. Therefore, in the molding requirements, appropriate drug additives and external environmental factors (such as time, temperature, pressure, etc.) must be used to destroy the unsaturated bond, and then Combine it with a saturated bond and vacuum assist to push the contained air completely out. In this way, the molded rubber can be used to achieve its desired characteristics. If there is any lack of molding process (such as incorrect formulation, lack of time, improper temperature, etc.), physical property loss, excess drug release, deformation, accelerated aging, and various serious adverse phenomena may occur.
Fifth, the rubber aging phenomenon:
According to the environmental conditions of the rubber products, the phenomenon of cracking or hardening and degradation of rubber properties over time is called aging phenomenon. Causes of aging, external factors and internal factors:
1. External factors: external factors such as oxygen, oxides, ozone, heat, light, radiation, mechanical fatigue, and lack of processing.
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