Definition of plastic
Plastic refers to the resin (or direct polymerization of monomers used in the process of processing) as the main component, plasticizers, fillers, lubricants, colorants and other additives as ancillary components, in the process of flow molding material.
Plastics mainly have the following characteristics: 1 Most plastics are light in weight, chemically stable, and will not rust; 2 have good impact resistance; 3 have good transparency and wear resistance; 4 good insulation and low thermal conductivity; 5 General moldability, good coloring, low processing cost; 6 Most plastics have poor heat resistance, high thermal expansion rate, easy to burn; 7 poor dimensional stability, easily deformed; 8 Most plastics have poor low temperature resistance and become brittle at low temperatures; Aging; 10 Some plastics are easily dissolved in solvents.
Classification of plastics
Classification according to use characteristics Classification by physical and chemical characteristics Classification by processing method
First, classified by use characteristics
According to the different types of plastics used, the plastics are usually divided into general plastics, engineering plastics and special plastics.
1 General plastic
Generally refers to the production of large, widely used, good moldability, cheap plastic, such as polyethylene, polypropylene, phenolic and so on.
2 Engineering plastics
General fat can withstand a certain external force, has good mechanical properties and high and low temperature resistance, good dimensional stability, can be used as engineering structure of plastics, such as polyamide, polysulfone and so on.
In engineering plastics, it is divided into general engineering plastics and special engineering plastics.
General engineering plastics include: polyamide, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, ultra high molecular weight polyethylene, methyl pentene polymer, vinyl alcohol copolymer, and the like.
Special engineering plastics are cross-linked non-cross-linked types. Cross-linked types include: polyaminobismaleimides, polytriazines, cross-linked polyimides, heat-resistant epoxy resin fingers, and the like. Non-cross-linked types include polysulfone, polyethersulfone, polyphenylene sulfide, polyimide, polyetheretherketone (PEEK), etc.
3 special plastic
Generally refers to plastics with special functions that can be used in special applications such as aviation and aerospace. Such as fluoroplastics and silicones have outstanding high-temperature, self-lubricating and other special functions. Reinforced plastics and foams have special properties such as high strength and high cushioning. These plastics belong to the category of special plastics.
a. Strong plastic: Reinforced plastic raw material can be divided into granular (such as calcium plastic reinforced plastic), fibrous (such as glass fiber or glass cloth reinforced plastic), and sheet (such as mica reinforced plastic) in shape. According to the material can be divided into cloth-based reinforced plastic (such as rag reinforced or asbestos-reinforced plastic), inorganic mineral-filled plastic (such as quartz or mica-filled plastic), fiber-reinforced plastic (such as carbon fiber-reinforced plastic) three.
b. Foam: Foam can be divided into three types: hard, semi-rigid, and flexible foam. Rigid foam is not flexible, compression hardness is very large, only to reach a certain stress value will produce deformation, the stress can not be restored after the original; soft foam is rich in flexibility, compression hardness is very small, very easy to deform, the stress can be relieved To restore the original state, the residual deformation is small; the flexibility and other properties of the semi-rigid foam are between the rigid and his flexible foam.
Second, classification by physical and chemical characteristics
According to different physical and chemical properties of various plastics, plastics can be divided into thermosetting plastics and thermoplastic plastics.
(1) Thermosetting plastics Thermosetting plastics are plastics that can be cured or have insoluble (melt) properties under heat or other conditions, such as phenolic plastics, epoxy plastics, and the like. Thermosetting plastics are divided into formaldehyde cross-linked type and other cross-linked types.
Crosslinked formaldehyde plastics include phenolic plastics, aminoplasts (such as urea-formaldehyde-melamine-formaldehyde, etc.).
Other cross-linked plastics include unsaturated polyesters, epoxy resins, phthalate resins, and the like.
(2) Thermoplastic plastics Thermoplastic plastics are plastics that can be repeatedly heated, softened, and cooled and hardened within a specific temperature range, such as polyethylene, polytetrafluoroethylene, and the like. Thermoplastic plastics are classified into hydrocarbons, vinyls containing polar genes, engineering, and cellulose.
1 Hydrocarbon plastics. Is a non-polar plastic, with crystalline and non-crystalline points, crystalline hydrocarbon plastics, including polyethylene, polypropylene, etc., non-crystalline hydrocarbon plastics including polystyrene and so on.
2 Vinyl plastics containing polar genes. Except fluorine plastics, most of them are non-crystalline transparent bodies, including polyvinyl chloride, polytetrafluoroethylene, polyvinyl acetate and so on. Most vinyl monomers can be polymerized using free-radical catalysts.
3 thermoplastic engineering plastics. Including polyoxymethylene, polyamide, polycarbonate, ABS, polyphenylene oxide, polyethylene terephthalate, polysulfone, polyether sulfone, polyimide, polyphenylene sulfide and so on. Teflon. Modified polypropylene and the like are also included in this range.
4 thermoplastic cellulose plastics. Mainly include cellulose acetate, cellulose acetate butyrate, stopper, cellophane and so on.
Third, classified by processing method
According to different molding methods of various plastics, it can be divided into membrane pressure, lamination, injection, extrusion, blow molding, cast plastic and reaction injection plastic and many other types.
Membrane pressure plastics are mostly plastics with similar physical properties and general solid plastics. Laminate plastics are fiber fabrics impregnated with resin, and they are combined and pressed together to form a unitary material; injection, extrusion and blowing Plastics are plastics with similar physical properties and processing properties to general thermoplastics. Casting plastics are liquid resin blends that can be hardened into a certain shape in a mold, such as MC, under pressureless or slight pressure. Nylon, etc.; reaction injection plastic is a liquid raw material, pressure injection into the cavity of the membrane, so that the reaction curing into a certain shape of the plastic products, such as polyurethane.
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