Definition, classification and characteristics of plastics

日期:2019/11/28 8:48:36 / 阅读: / 来源:本站

Definition, classification and characteristics of plastics

Plastic is a kind of material that uses synthetic or natural polymer resin as the main material. After adding various auxiliaries, it has ductility under a certain temperature and pressure. After cooling, it can fix its shape. The process of natural or synthetic polymer resin molecules in the molten state and uniform distribution of the auxiliary molecules is called plasticization. This process has been reached, which has been plasticized, has not yet been reached, and is considered to have not been plasticized.

Plastics can be divided according to their own properties: thermoplastics which can be repeatedly melt-molded repeatedly to maintain their characteristics and thermosetting plastics which can only be melt-molded once. According to its use, it can be divided into general-purpose plastics that have a wide range of uses, are cheap, and have good comprehensive properties, such as: PE, PP, PVC, PS, phenolic plastics, and amine-based plastics; they have good physical and mechanical strength and may replace metals. Engineering plastics used in construction machinery, such as: ABS, nylon, polyester, POM, TPX-1; and a class of engineering plastics that have particularly good performance in certain properties, such as: have particularly good radiation resistance, Special plastics such as high temperature resistance, such as: polyarylsulfone, polyetheretherketone, liquid crystal polymer, etc. According to the degree of crystallinity of thermoplastic resin molecules, thermoplastics can be divided into two types: amorphous polymers and crystalline polymers.

The main characteristics of plastic are: first, small density, high specific strength, can obtain higher packaging yield (yield), that is, the unit volume of packaging volume or packaging area is larger (m2 / kg, m2 / kg); Second, most plastics have good chemical resistance.

Good resistance to acids, alkalis and various organic solvents, long-term storage without oxidation corrosion; third, easy to form, the energy required for forming is lower than metal materials such as steel; fourth, it has good transparency and easy Colorability; Fifth, has good strength, high strength per unit weight, impact resistance, easy to modify; sixth, low processing cost; seventh, excellent insulation. However, plastics also have some disadvantages: first, most plastics have poor heat resistance, all below 300 ° C. Above this temperature, plastics are easy to decompose, and the use temperature is lower for this purpose; , Easy to be brittle at low temperatures; fourth, susceptible to the effects of oxygen, force, light, heat, and aging.

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