Plastic definition and classification

Definition of plastic

Plastic refers to a material that can be flow-formed during processing by using a resin (or a monomer directly polymerized during processing) as a main component, and an additive such as a plasticizer, a filler, a lubricant, or a coloring agent as an auxiliary component.
The plastic has the following characteristics: 1 Most plastics are light in weight, good in chemical stability, and will not rust; 2 good impact resistance; 3 have good transparency and wear resistance; 4 good insulation and low thermal conductivity; 5 general formability, good colorability, low processing cost; 6 most plastics have poor heat resistance, large thermal expansion rate, easy to burn; 7 dimensional stability is poor, easy to deform; 8 most plastics have poor low temperature resistance, become brittle at low temperature; Aging; 10 some plastics are easily soluble in solvents.


Plastic classification

According to the classification of use characteristics, according to the classification of physical and chemical properties, according to the processing method

First, classified by usage characteristics

According to the different use characteristics of famous plastics, plastics are generally divided into three types: general plastics, engineering plastics and special plastics.


1 general plastic


Generally speaking, it refers to plastics with large output, wide application, good formability and low price, such as polyethylene, polypropylene, phenolic and the like.

2 engineering plastics


Generally, the fat can withstand a certain external force, has good mechanical properties and high and low temperature resistance, and has good dimensional stability, and can be used as an engineering structural plastic such as polyamide or polysulfone.
In engineering plastics, it is divided into two categories: general engineering plastics and special engineering plastics.
General engineering plastics include: polyamide, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, ultra high molecular weight polyethylene, methylpentene polymer, vinyl alcohol copolymer and the like.
Special engineering plastics also have a cross-linked type of non-crosslinking type. Crosslinking types include polyaminobismaleamide, polytriazine, crosslinked polyimide, heat resistant epoxy tree, and the like. Non-crosslinked types include polysulfone, polyethersulfone, polyphenylene sulfide, polyimide, polyetheretherketone (PEEK), etc.

3 special plastics


Generally refers to plastics with special functions that can be used in special applications such as aviation and aerospace. For example, fluoroplastics and silicones have outstanding special functions such as high temperature resistance and self-lubrication, and reinforced plastics and foams have special properties such as high strength and high cushioning properties. These plastics belong to the category of special plastics.
a. Strong plastic: Reinforced plastic raw materials can be divided into three types: granular (such as calcium plastic reinforced plastic), fibrous (such as glass fiber or glass cloth reinforced plastic), and sheet (such as mica reinforced plastic). According to the material, it 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), and fiber reinforced plastic (such as carbon fiber reinforced plastic).
b. Foam: Foam can be divided into three types: hard, semi-rigid and flexible foam. Rigid foam has no flexibility and has a high compression hardness. It only deforms when it reaches a certain stress value. It can not be restored after the stress is relieved. The flexible foam is flexible, has a small compression hardness, and is easily deformed. Reverted to its original shape with less residual distortion; the flexibility and other properties of semi-rigid foam are between the hard and soft foams.

Second, according to physical and chemical characteristics


According to the different physical and chemical properties of various plastics, plastics can be divided into two types: thermosetting plastics and thermoplastic plastics.
(1) Thermosetting plastics Thermosetting plastics are plastics that can be cured or have insoluble (melting) properties under heat or other conditions, such as phenolic plastics, epoxy plastics, and the like. Thermosetting plastics are divided into two types: formaldehyde cross-linking type and other cross-linking type.
Formaldehyde cross-linking plastics include phenolic plastics, aminoplasts (such as urea-formaldehyde-melamine-formaldehyde, etc.).
Other crosslinked plastics include unsaturated polyesters, epoxy resins, phthalyl acrylate resins, and the like.
(2) Thermoplastic plastics Thermoplastic plastics are plastics that can be repeatedly softened and cooled and hardened in a specific temperature range, such as polyethylene and polytetrafluoroethylene. Thermoplastic plastics are also classified into hydrocarbons, vinyls containing polar genes, engineering, and cellulose.
1 hydrocarbon plastic. It is a non-polar plastic with crystallinity and non-crystallinity. The crystalline hydrocarbon plastics include polyethylene, polypropylene, etc., and the non-crystalline hydrocarbon plastics include polyphenylene.
2 vinyl-based plastics containing polar genes. Most of the fluorine-containing plastics are amorphous transparent bodies, including polyvinyl chloride, polytetrafluoroethylene, polyvinyl acetate and the like. Most of the vinyl monomers can be polymerized using a free radical catalyst.
3 thermoplastic engineering plastics. It mainly includes polyoxymethylene, polyamide, polycarbonate, ABS, polyphenylene ether, polyethylene terephthalate, polysulfone, polyethersulfone, polyimide, polyphenylene sulfide and the like. Polytetrafluoroethylene. Modified polypropylene and the like are also included in this range.
4 thermoplastic cellulose plastics. It mainly includes cellulose acetate, cellulose acetate butyrate, sputum, cellophane and the like.

Third, according to processing methods


According to different molding methods of various plastics, it can be divided into various types such as film pressing, laminating, injection, extrusion, blow molding, casting plastic and reaction injection plastic.
Membrane pressure plastics are mostly plastics whose physical properties are similar to those of general solid plastics; laminated plastics are fabrics impregnated with resin, which are combined into a whole by superposition and hot pressing; injection, extrusion and blowing Plastic is a plastic similar in physical properties and processing properties to general thermoplastics; cast plastic refers to a liquid resin mixture that can be hardened into a certain shape in a mold without pressure or a slight pressure, such as MC. Nylon, etc.; reaction injection plastic is a plastic which is injected into a film cavity by a liquid raw material, and is reacted and solidified into a certain shape product, such as polyurethane.

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