Classified by physicochemical properties
According to a variety of different physical and chemical properties of plastic, you can put plastic into thermosetting plastics and thermoplastic plastics types.
⑴ thermosetting plastics
It refers thermosetting plastics under heat or other conditions can be cured or with insoluble (melt) plastic characteristics, such as phenolics, epoxy plastic. Thermosetting plastic was divided formaldehyde cross-linking and other cross-linking of two types. When heated to soften, harden when cooled, can repeatedly soften and harden and maintain a certain shape. Soluble in certain solvents, having a fusible soluble nature. Thermoplastics with excellent electrical insulation properties, in particular polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene (PE), polypropylene (PP) has a very low dielectric constant and dielectric loss, should for use as a high-frequency and high-voltage insulation material. Thermoplastic easy molding, but low in heat resistance, easy to creep, with the degree of creep under load, the ambient temperature, the solvent, the humidity varies. To overcome these weaknesses thermoplastics, meet the need of space technology, new energy development and other fields, countries are developing melt molding heat-resistant resin, such as polyether ether ketone (PEEK), polyether sulfone (PES) , polyarylsulfone (PASU), polyphenylene sulfide (PPS) and the like. To them as a matrix resin composite material having high mechanical properties and chemical resistance, thermoforming and welding between energy, interlaminar shear strength is better than epoxy resin. As with PEEK as a matrix resin and carbon fiber composite materials, the fatigue resistance than epoxy / carbon fiber. Its good impact resistance, excellent creep resistance at room temperature, process, and can be used continuously at 240 ~ 270 ℃, it is an ideal high temperature insulation material. It has high strength and hardness at 200 ℃ with PES as a composite material matrix resin and carbon fibers, at -100 ℃ can still maintain good impact resistance; non-toxic, non-flammable, fuming at least, radiation resistance Well, the key components for the spacecraft is expected to use it, but also molding into a radome and the like.
Formaldehyde-crosslinked plastics include phenolics, aminoplasts (such as urea - formaldehyde - melamine - formaldehyde, etc.).
Other cross-linked plastics include unsaturated polyesters, epoxy resins, diallyl phthalic acid resins and the like.
⑵ thermoplastic plastic
Refers to thermoplastic plastics can be repeatedly softened by heating and hardened by cooling of the plastic, such as polyethylene, polytetrafluoroethylene or the like within a specific temperature range. Thermoplastic plastic was divided hydrocarbons, vinyl containing polar gene engineering, cellulose and other types. After thermo-forming insoluble infusible form a cured resin molecules by the linear structure of its cross-linked into a network structure. Thermal decomposition will again strengthen damage. Typical phenolic thermosetting plastic, epoxy, amino, unsaturated polyesters, furan, polysiloxane and other materials, as well as newer polyethylene phthalate and propylene carbonate plastic or the like. They have high heat resistance, heat easily deformed and so on. The disadvantage is that the mechanical strength is generally not high, but by adding fillers, made of laminate or molding material to improve its mechanical strength.
Phenolic resin as the main raw material of thermosetting plastics, such as phenolic molded plastic (commonly known as Bakelite), with a durable, dimensionally stable, resistant to other chemicals in addition to strong base effects and other characteristics. According to different purposes and requirements, the addition of various fillers and additives. Such as requiring high insulation performance of varieties, can be mica or glass fiber as filler; to resistant varieties, may be asbestos or other heat-resistant filler; species such as seismic requirements, various appropriate fiber or rubber filler and a number of toughening agent to produce high toughness materials. Further aniline may also be used, epoxy, polyvinyl chloride, polyamide, polyvinyl acetal-modified phenolic resin, etc. to meet the requirements of different applications. It can also be made with phenolic resin phenolic laminate, which is characterized by high mechanical strength, good electrical properties, corrosion resistance, easy processing, widely used in low-voltage electrical equipment.
Aminoplast have urea formaldehyde, melamine-formaldehyde, melamine urea formaldehyde. They have a hard, scratch-resistant, colorless, translucent, etc., can be added to products made of bright color pigment, commonly known as Bakelite. Because of its oil, affected by the weak base and an organic solvent (but not acid), long-term use at 70 ℃, short-term resistant to 110 ~ 120 ℃, can be used electrician products. Melamine formaldehyde plastic plastic hardness than urea formaldehyde, have better water resistance, heat resistance, arc resistance, arc resistant insulating material can be used.
Epoxy resin as the main raw material of thermosetting plastic varieties, many of them with a bisphenol A type epoxy resin as a base of about 90%. It has excellent adhesion, electrical insulation, heat resistance and chemical stability, shrinkage and water absorption, good mechanical strength and other characteristics.
Unsaturated polyester and epoxy resins can be made of glass steel, it has excellent mechanical strength. Such as unsaturated polyester, glass, steel, good mechanical properties, low density (only 1/5 to 1/4 of steel, aluminum, 1/2), easily processed into a variety of electrical components. Electrical and mechanical properties of plastics to phthalate acrylate resin are better than phenolic and amino thermoset plastic. It is hygroscopic small, products dimensional stability, good moldability acid and boiling water and some organic solvents. Molding plastic suitable for manufacturing complex structure, both have high temperature insulation parts. Usually long-term use in the temperature range of -60 ~ 180 ℃, the heat levels up F grade to H level, higher than the phenolic and amino plastic heat resistance.
Polysiloxane structure in the form of silicone plastic used more often in Electronics & Electrical Technology. Silicone laminated plastic over glass cloth as reinforcement material; silicone molded plastic over glass fibers and asbestos packing, for the manufacture of high temperature, high or submersible motors, electrical appliances, electronic equipment parts. Such plastics are characterized by a small dielectric constant and tgδ value, by the frequency of small, for electricians and electronics industry corona resistance and arc discharge even cause decomposition, the product is capable of conducting silica rather than carbon black ʱ?? Such materials have outstanding heat resistance, can be used continuously at 250 ℃. The main disadvantage of polysiloxane is low mechanical strength, adhesiveness small, oil poor. Has developed a number of modified silicone polymers, such as plastics, polyester-modified silicone technology has been applied in the electrician. Some plastic both thermoplastic and thermosetting plastics. Such as polyvinyl chloride, usually thermoplastics, Japan has developed a new type of liquid PVC is thermosetting molding temperature of 60 ~ 140 ℃; Lund plastic American called Alex, both thermoplastic processing features, there are the physical properties of thermoset plastics.
① hydrocarbon plastics. Is a non-polar plastics, crystalline and non-crystalline points, crystalline hydrocarbon plastics include polyethylene, polypropylene, non-crystalline hydrocarbon plastics, including polystyrene and the like.
② vinyl plastic containing polar gene. Fluorine plastic, most non-crystalline transparent body, including polyvinyl chloride, polytetrafluoroethylene, polyvinyl acetate and the like. Most vinyl-based monomer may be polymerized using a free radical catalyst.
③ engineering thermoplastics. Including polyoxymethylene, polyamide, polycarbonate, ABS, polyphenylene oxide, polyethylene terephthalate, polysulfone, polyether sulfone, polyimides, polyphenylene sulfide and the like. Polytetrafluoroethylene. Modified polypropylene or the like are also included in this range.
④ thermoplastic cellulose-based plastics. It includes cellulose acetate, cellulose acetate butyrate, celluloid, cellophane and the like.
Third, according to the processing method of classification
According to the different kinds of plastic molding methods can be divided into membrane pressure, lamination, injection, extrusion, blow molding, reaction injection molding plastics and other types of plastic.
Membrane pressure, mostly plastic processing performance and general properties similar to solid plastic plastic; laminated plastic means of fabric impregnated with resin, the laminated, hot materials incorporated as a whole; injection, extrusion and blow mostly plastic properties and processability of thermoplastics with generally similar plastic; means capable of molding plastic under no pressure or little pressure, poured in a mold shaped article can harden into a liquid resin mixture, such as MC nylon; Reaction Injection plastic material with a liquid, the membrane cavity injection pressure, and allowed to react solidified into shaped articles of plastic, such as polyurethane or the like.