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Common crystalline polymers

by:CSSSLD     2021-01-23
If the force comes from one direction, the molecular chain of one-way orientation, if come from the same plane perpendicular directions, the molecular chain is two-way orientation. The passive process orientation is under the action of external force. Both crystalline polymer injection molding processing, and amorphous polymers, can be in a certain temperature range, on orientation structure under the action of the form, but the crystalline polymer orientation than the amorphous polymer orientation is relatively stable.

in fact, is generally thought that some of the amorphous polymer, is not completely unable to crystallization. Polyvinyl chloride (PVC), for example, according to there is also a small amount of crystal structure determination. And polycarbonate, it is crystallization conditions are very harsh, general condition is not easy to get the crystal structure, so it is regarded as amorphous polymers. Within the crystalline polymer molecular chain is not totally formed crystals can regularly arranged.

due to the molecular chain tends to have a free curl under high temperature, when the external force is applied to the molecular chain can stretch. Many stretch chain along the direction of an orderly arrangement, the action of forces are formed orientation, will have been formed orientation of the polymer to reduce the temperature, the frozen and orientation structure will be retained in the products. Orientation state and amorphous is characterized by high polymer arranged orderly, the difference is that amorphous is three-dimensional and orderly, and spontaneously generated under suitable environmental conditions, and orientation is a one-dimensional or two-dimensional orderly.

in the process of crystal formation, there may be a most macromolecular crystallization or macromolecular chain segment has no chance, become the amorphous part of the polymer. Crystal part in proportion as crystallinity of polymer. Different varieties of polymer, crystallization ability is different, depending on its structural differences, high crystallinity can reach 90%, while crystalline polymer crystallinity is usually around 50%.

the same variety of polymers is due to structural differences, which affect the degree of crystallinity. Low density polyethylene, for example, since it has more branched chain, the chain of the regularity of received damage, and crystallinity under linear high-density polyethylene. Crystal is in the process of forming, the polymer in the viscous flow of the melt, in close to a temperature below the melting point area, gradually formed on cooling.

polymer chain can be arranged according to certain format, so is the gravitational force and phase equilibrium are results of fixed in the position of the molecules. Has a crystalline structure, or polymer called crystalline polymer to form crystalline structure. By contrast, in a larger scale or local area, molecular chain arrangement in disorder, is defined as functional. Where there are no conditions can crystal called amorphous polymer injection tooling.

due to different process conditions, the vast majority of crystalline polymer, can be in the crystalline state, can also be in amorphous. In crystalline polymers, due to the condition of different forming crystal, crystal degree is not the same. Amorphous and functional are two different types of aggregation state, therefore, lead to bigger difference on the performance is also inevitable. Peculiar to the orientation of macromolecule material, which related to its chain length and width of the huge contrast.

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