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Rubber block
Rubber block
Product Details

Rubber block: highly resilient polymer material with reversible deformation. Elastic at room temperature, in a very small

Under the external force can produce a large deformation, remove the external force can restore the original. Rubber is completely amorphous polymer, its glass transition temperature (T g) is low, the molecular weight is often large, more than a few hundred thousand.
The word rubber comes from the Indian word cau-uchu, meaning "the tree of tears." Natural rubber is the rubber from the three-leaf rubber tapping out of the latex through the solidification, drying and prepared in 1770, the British chemist J. Pulis Terry found that rubber can be used to wipe the pencil writing, then the use of this material is called rubber, the word has been used so far. Rubber molecular chain can be cross-linked, cross-linked rubber by external action deformation, with rapid The ability to restore, and has good physical and mechanical properties and chemical stability. Rubber is the rubber industry, the basic raw materials, widely used in the manufacture of tires, hoses, tapes, cables and other rubber products.
The three-leaf rubber tree provides the most commercial rubber, and it secures a large amount of sap containing the rubber emulsion when it is damaged (as the bark of the stem is cut).
In addition, figs and some Euphorbiaceae plants can also provide rubber. Germany in the Second World War because the rubber supply was cut off, had tried to obtain rubber from these plants, but later changed to the production of synthetic rubber.
The original rubber tree grows in South America, but after artificial transplantation, Southeast Asia also has a large number of rubber trees. In fact, Asia has become the most important source of rubber.
Rubber made from silver chrysanthemum can reduce sensitivity.
Natural rubber is made from latex, latex contains a part of the non-rubber components to stay in the solid natural rubber. General natural rubber containing rubber 92% -95%, while rubber hydrocarbons accounted for 5% -8% Due to the different manufacturing methods, different origin and even the seasons are different, the proportion of these components may be different, but basically in the range.
Protein can promote the vulcanization of rubber, delay aging.On the other hand, the protein has a strong water absorption, can cause rubber moisture absorption mold, insulation decreased, the protein also increase the shortcomings of heat.
Acetone extract is a number of higher fatty acids and sterols, some of which from the natural antioxidant and accelerator effect, and some can help powder mixing agent in the mixing process and the softening effect of raw rubber.
Ash mainly contains magnesium phosphate and calcium phosphate and other salts, there are very few copper, manganese, iron and other metal compounds, because these valence metal ions can promote the aging of rubber, so their content should be controlled.
Dry glue in the water does not exceed 1%, can be volatile in the processing process, but too much moisture content, not only will make raw rubber storage process easy moldy, but also affect the processing of rubber, such as mixing when the agent easy to knot Group; calendering, extrusion process is easy to produce bubbles, vulcanization process occurs in the bubble or sponge-like and so on.
Linear structure: the general structure of unvulcanized rubber.As the molecular weight is large, no external force, the macromolecule chain was random coil curve group.When the external force, remove the external force, the entanglement of the coil changes, the molecular chain rebound , Resulting in a strong tendency to restore, which is the origin of high elastic rubber.
Branches: the chain of rubber macromolecules chain aggregation, the formation of gel. Gel on the rubber properties and processing are adverse. In the rubber refining, a variety of complexing agent can not enter the gel area, the formation of local blank, the formation of Not reinforcement and cross-linking, a weak part of the product.
Cross-linked structure: Linear molecules through some atoms or atomic groups of the bridge and connected to each other to form a three-dimensional network structure with the vulcanization process, this structure continues to strengthen, so that the free flow capacity of the segment decreased, plasticity And elongation decreases, strength, elasticity and hardness rise, compression set and swelling degree of decline.
The source and application of general purpose rubber
General rubber has a comprehensive performance, widely used. Mainly: ① natural rubber, rubber from the three-leaf rubber latex, the basic chemical composition of cis-polyisoprene. Good elasticity, high strength, good overall performance. ② isoprene rubber, the full name of cis-1,4-polyisoprene rubber, made from isoprene high cis-synthetic rubber, because of its structure and performance and natural rubber approximation, it is also known as synthetic natural Rubber. ③ SBR, referred to as SBR, produced by the copolymer of butadiene and styrene.According to the production method is divided into emulsion polymerization styrene-butadiene rubber and solution polymerization styrene-butadiene rubber. Its comprehensive performance and chemical stability is good. Rubber, the full name of cis-1,4-polybutadiene rubber, referred to as BR, made by the polymerization of butadiene.Compared with other general-purpose rubber, vulcanized butadiene rubber cold resistance, wear resistance and Elasticity is particularly excellent, less heat under the load, anti-aging performance, and easy with natural rubber, chloroprene rubber, nitrile rubber, etc. combined with chloroprene rubber, referred to as CR, made from chloroprene polymerization.
Good overall performance, oil resistance, fire resistance, oxidation resistance and ozone resistance, but its density is large, easy to crystallize at room temperature hard, poor storage, poor cold resistance.
Special rubber source and application characteristics
Special rubber refers to the rubber with some special properties. Mainly: ① nitrile rubber, referred to as NBR, from butadiene and acrylonitrile copolymerization. Oil resistance, anti-aging performance, can be 120 ℃ in the air or in 150 ℃ oil in the long-term use. In addition, also has water resistance, air tightness and excellent bonding performance. ② silicone rubber, the main chain composed of silicon atoms alternately in the silicon atom with organic groups. Low temperature, ozone resistance, good electrical insulation. ③ fluorine rubber, molecular structure containing fluorine atoms of synthetic rubber. Usually in the copolymer fluorine-containing units to the number of fluorine atoms, such as fluorine rubber 23, is vinylidene fluoride Chlorinated rubber high temperature, oil resistance, chemical resistance. ④ polysulfide rubber, from dihaloalkane and alkali or alkaline earth metal polysulfide polycondensation made of excellent oil and solvent resistance, But the strength is not high, anti-aging, processing is not good, there are odor, and more with nitrile rubber. In addition, there are polyurethane rubber, chloroprene rubber, acrylic rubber.
The effect of rubber structure
The main effect of rubber reinforcement on the tensile strength and tear strength, the general rule is: when the same particle size, the high structural carbon black on the non-crystalline rubber reinforcement effect, generally have a higher tensile strength And tear strength. Rubber structural or affect the conductivity of the most important factor, the chain structure is easy to form in the rubber intertwined conductive path, will improve the conductivity.
Rubber classification
According to raw materials and methods: rubber can be divided into two categories of natural rubber and synthetic rubber, of which natural rubber consumption accounted for 1/3, synthetic rubber consumption accounted for 2 /
According to the appearance of rubber: rubber can be divided into solid rubber (also known as dry rubber), milky rubber (latex), liquid rubber and powder rubber four categories.
According to the performance and use of rubber: In addition to natural rubber, the synthetic rubber can be divided into general synthetic rubber, semi-general synthetic rubber, special synthetic rubber and special synthetic rubber.
According to the physical form of rubber: rubber can be divided into hard plastic and soft, raw rubber and rubber and so on.
By performance and use points: General rubber and special rubber.

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