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questions :Properties of polymer
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[Member (365WT)]answers [Chinese ]Time :2019-07-02
Polymer molecules (also known as high polymers) have much larger molecules than low molecular organic compounds. Generally, the relative molecular mass of the organic compound does not exceed 1000, and the relative molecular mass of the polymer compound can be as high as 1.0 to 1.06 million. Since the relative molecular mass of the polymer compound is large, it is largely different from the low molecular compound in physical, chemical, and mechanical properties.

Although the relative molecular mass of macromolecular compounds is large, the composition is not complicated, and their molecules are often formed by repeated reconnection of specific structural units through covalent bonds.
The molecular chain of the same polymer compound does not have the same number of links, so the polymer compound is essentially a mixture of a plurality of compounds having the same structure and different degrees of polymerization, and the relative molecular mass and degree of polymerization are both It is the average.

The polymer compound is almost non-volatile and often exists in a solid or liquid state at normal temperature. Solid polymers can be classified into crystalline and amorphous states according to their structural forms. The former is arranged in a regular order; the latter is arranged irregularly. The same polymer compound can have both crystalline and amorphous structures. Most synthetic resins are amorphous.
The atoms constituting the polymer chain are bonded by a covalent bond, and the polymer chain generally has two different shapes of a chain shape and a body shape.

A large number of polymer compounds used as materials in the world are made of coal, petroleum, natural gas, etc., and low molecular organic compounds are produced by polymerization. These low molecular compounds are called "monomers", and polymer compounds formed by their polymerization are also called high polymers. The polymerization reaction is generally divided into two types of addition polymerization and condensation polymerization, referred to as polyaddition and polycondensation.
A reaction in which one or more monomers are added to each other and combined into a polymer compound is called a polyaddition reaction. No other by-products were produced during the reaction, and the chemical composition of the resulting polymer was substantially the same as that of the monomer.

The polycondensation reaction refers to a reaction in which one or more monomers are condensed with each other to form a high polymer, and other low molecular compounds such as water, ammonia, an alcohol, a hydrogen halide, and the like are precipitated. The chemical composition of the high polymer produced by the polycondensation reaction is different from that of the monomer. Polymers have their own laws from relative molecular mass to composition, from structure to performance, from synthesis to application. In order to synthesize it and use it, you need to establish some basic concepts.

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