The hottest basic knowledge about plastics I

2022-08-06
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Basic knowledge about plastics (I)

I. definition of plastics

plastics are high molecular organic materials that take resin as the main component, form a certain shape under a certain temperature and pressure, and can maintain a given shape at room temperature

resin refers to an organic polymer that usually has a transformation or melting range when heated, has fluidity under external force during transformation, and is solid, semi-solid or liquid at room temperature. It is the most basic and important component of plastics. Broadly speaking, any polymer used as the basic material of plastics in the plastic industry can be called resin

II. Classification of plastics

at present, there is no exact classification of plastics. The general classification is as follows:

1. according to the physical chemistry of plastics to reduce the pulsation, the component performance is divided into

thermoplastics: plastics that can be repeatedly heated, softened, cooled and hardened within a specific temperature range. Such as polyethylene plastic, PVC plastic

thermosetting plastics: plastics that can solidify into insoluble materials due to heating or other conditions. Such as phenolic plastic, epoxy plastic, etc

2. select according to plastic use

General Plastics: - generally refers to plastics with large output, wide use, good formability and low price. Such as polyethylene, polypropylene, polyvinyl chloride, etc

Engineering Plastics: - generally refers to plastics that can withstand certain external forces, have good mechanical properties and dimensional stability, and can maintain its excellent performance at high and low temperatures, and can be used as engineering structural parts. Such as ABS, nylon, poly alum, etc

special plastics: - generally refers to plastics with special functions (such as heat resistance, self lubrication, etc.) and applied to special requirements. Such as fluoroplastics, organosilicon, etc

3. according to the plastic forming method,

molded plastics: resin mixture for molding. Such as general thermosetting plastics

laminated plastic: refers to the fiber fabric impregnated with resin, which can be laminated and hot pressed to form an integral material

injection, extrusion and blow molding plastics: - generally refers to the resin mixing section that can melt and flow at the barrel temperature and harden rapidly in the mold. Such as general thermoplastic

cast plastic: it is a liquid resin mixture that can be poured into a mold without pressure or with a little pressure and can harden into a certain shape product. Such as MC nylon

reaction injection molding compound: generally, it refers to liquid raw materials, which are pressurized and injected into the mold cavity, so that the inspection method is to cut off the output signal of the amplifier unit and react and solidify to produce the finished product. Such as polyurethane

4. according to plastic semi-finished products and products,

molding powder: also known as plastic powder, it is mainly obtained by fully mixing, pressing and crushing thermosetting resin (such as phenolic resin) and filler. Such as phenolic plastic powder

reinforced plastics: a kind of plastics with reinforced materials and some mechanical properties greatly improved compared with the original resin

foamed plastic: plastic with numerous micropores inside

film: generally refers to flat and soft plastic products with a thickness of less than 0.25 mm

in addition, engineering plastics, reinforced plastics and foamed plastics have different categories, as shown in the following table:

classification of engineering plastics

category polymer

general engineering plastics nylon, polyoxymethylene, polycarbonate, modified polyphenylene oxide, thermoplastic polyester, ultra-high molecular weight polyethylene, methylpentene polymer, vinyl alcohol copolymer, etc.

special engineering plastics non crosslinked poly alum, polyether alum, polyphenylene sulfide Polyarylate, polyimide, peek, fluororesin, etc.

classification of cross-linked polyamine bismaleamide, polytriazine, cross-linked polyimide, heat-resistant epoxy resin, etc.

classification of reinforced plastics according to the shape of reinforced materials granular reinforced plastics such as calcium plastic fiber reinforced plastics such as glass fiber or glass cloth reinforced plastics sheet reinforced plastics such as mica reinforced plastics Asbestos reinforced plastics such as rag reinforced plastics, inorganic mineral filled plastics such as quartz, mica filled plastics, glass fiber reinforced plastics such as prepreg, SMC, BMC and other special fiber reinforced plastics such as carbon fiber, Kevlar fiber reinforced plastics, metal fiber reinforced plastics such as steel wire reinforced plastics, When the stress reaches a certain value, the deformation will occur. After the stress is relieved, the foam plastic that instinctively recovers to its original state

semi-rigid foam plastic flexibility is between hard and soft foam plastic

soft foam plastic is flexible and has very small compression hardness. After the stress is relieved, it can recover to its original state. The foam plastic with small residual deformation

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