Classification of plastics
Classification of Plastics-Find Xiamen Dacheng for Processing Special Thick Plates
Use classification
According to the different use characteristics of various plastics, plastics are usually divided into three types: general plastics, engineering plastics and special plastics.
① General-purpose plastics
Generally refers to the large output, wide use, good formability, cheap plastic. General plastic
There are five major varieties of materials, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and acrylonitrile-butadiene-styrene copolymer (ABS). These five categories of plastics occupy the vast majority of the use of plastic raw materials, and the rest can be classified as special plastic varieties, such as PPS, PPO, PA, PC, POM, etc., which are used in daily life products. It is mainly used in high-end fields such as engineering industry, national defense technology, such as automobiles, aerospace, construction, communications and other fields. Plastics are classified according to their plasticity and can be divided into thermoplastics and thermosetting plastics. Under normal circumstances, thermoplastic products can be recycled, while thermosetting plastics cannot. According to the optical properties of plastics, they can be divided into transparent, translucent and opaque raw materials, such as PS, PMMA, AS, PC, etc., which are transparent plastics, while most other plastics are opaque plastics.
Commonly used plastic varieties performance and use
1. Polyethylene: Commonly used polyethylene can be divided into low density polyethylene (LDPE), high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). Among the three, HDPE has better thermal properties, electrical properties and mechanical properties, while LDPE and LLDPE have better flexibility, impact properties, film-forming properties and so on. LDPE and LLDPE are mainly used for packaging film, agricultural film, plastic modification, etc., and HDPE is widely used, film, pipe, injection daily necessities and other fields.
2. Polypropylene: Relatively speaking, polypropylene has more varieties, complicated uses and various fields. The varieties mainly include homopolypropylene (homopp), block copolymer polypropylene (copp) and random copolymer polypropylene (rapp). According to different uses, homopolymerization is mainly used in wire drawing, fiber, injection, BOPP film and other fields. Copolypropylene is mainly used in injection parts of household appliances and modified raw materials, daily injection products, pipes, etc., random polypropylene is mainly used for transparent products, high-performance products, high-performance pipes, etc.
3. PVC: Because of its low cost, the product has the characteristics of self flame retardant, so it is widely used in the construction field, especially the sewer pipe, plastic steel doors and windows, plate, artificial leather and other uses are the most widely used.
4. Polystyrene: As a transparent raw material, it has a wide range of uses when there is a need for transparency, such as car lampshades, daily transparent parts, transparent cups, cans, etc.
5.ABS: is a widely used engineering plastic with outstanding physical, mechanical and thermal properties. It is widely used in household appliances, panels, masks, assemblies, accessories, etc., especially household appliances, such as washing machines, air conditioners, refrigerators, electric fans, etc. The amount is very large, and it is also widely used in plastic modification.
② Engineering plastics
Generally refers to the ability to 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 two categories: general engineering plastics and special engineering plastics. Engineering plastics can achieve higher requirements in terms of mechanical properties, durability, corrosion resistance, heat resistance, etc., and can be processed more conveniently and can replace metal materials. Engineering plastics are widely used in electronic and electrical, automobile, construction, office equipment, machinery, aerospace and other industries. Substituting plastic for steel and plastic for wood has become an international trend.
General engineering plastics include: polyamide, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, ultra-high molecular weight polyethylene, methyl pentene polymer, vinyl alcohol copolymer, etc.
Special engineering plastics are also cross-linked and non-cross-linked. Cross-linked types are: polyamino bismaleamide, polytriazine, cross-linked polyimide, heat-resistant epoxy tree fingers, etc. Non-crosslinked types include polysulfone, polyether sulfone, polyphenylene sulfide, polyimide, polyether ether ketone (PEEK), and the like.
③ Special plastics (for processing and making special plates and finished products, please find Xiamen Dacheng)
Generally refers to the special function, can be used for aviation, aerospace and other special applications of plastic. Such as fluorine plastics and silicone with outstanding high temperature, self-lubricating and other special functions, reinforced plastics and foam plastics with high strength, high cushioning and other special properties, these plastics belong to the category of special plastics.
a. Reinforced Plastics:
Reinforced plastic raw materials in the shape can be divided into granular (such as calcium plastic reinforced plastic), fibrous (such as glass fiber or glass cloth reinforced plastic), flake (such as mica reinforced plastic) three. According to the material can be divided into cloth 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 plastics can be divided into rigid, semi-rigid and flexible foams. Rigid foam has no flexibility, compression hardness is very large, only to reach a certain stress value to produce deformation, stress relief can not be restored to its original state; flexible foam is flexible, compression hardness is very small, it is easy to deform, stress relief can be restored to its original state, residual deformation is small; semi-rigid foam flexibility and other properties between hard and soft foam.
physical and chemical classification
According to the different physical and chemical properties of various plastics, plastics can be divided into two types: thermosetting plastics and thermoplastics.
(1) Thermoplastics
Thermoplastic (Thermo plastics ): refers to the melting after heating, can flow to the mold after cooling molding, and then heated and melted again; can use heating and cooling, make it produce reversible change (liquid →solid), is the so-called physical change. Universal thermoplastic its continuous use temperature below 100 ℃, polyethylene, polyvinyl chloride, polypropylene, polystyrene and called the four general plastics. Thermoplastic plastics are also divided into hydrocarbons, vinyl containing polar genes, engineering, cellulose and other types. It softens when heated and hardens when cooled, and can repeatedly soften and harden and maintain a certain shape. Soluble in certain solvents, with soluble properties. Thermoplastics have excellent electrical insulation, especially polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene (PE), polypropylene (PP) have a very low dielectric constant and dielectric loss, suitable for high frequency and high voltage insulation materials. Thermoplastics are easy to mold, but have low heat resistance and are easy to creep. The degree of creep varies with load, ambient temperature, solvent and humidity. In order to overcome these weaknesses of thermoplastics and meet the needs of applications in space technology, new energy development and other fields, countries are developing heat-resistant resins that can be melt-formed, such as polyetheretherketone (PEEK), polyethersulfone (PES), polyarylsulfone (PASU), and polyphenylene sulfide (PPS). Composites with them as matrix resins have high mechanical properties and chemical resistance, can be thermoformed and welded, and have better interlaminar shear strength than epoxy resins. If polyether ether ketone is used as a matrix resin and carbon fiber is used to make a composite material, the fatigue resistance exceeds that of epoxy/carbon fiber. It has good impact resistance, good creep resistance at room temperature, good processability, and can be used continuously at 240~270 ℃. It is a very ideal high temperature resistant insulating material. The composite material made of polyethersulfone as the matrix resin and carbon fiber has high strength and hardness at 200 ℃, and can still maintain good impact resistance at -100 ℃. It is non-toxic, non-flammable, has the least smoke and good radiation resistance. It is expected to be used as a key component of spacecraft and can also be molded into radar radome.
Formaldehyde cross-linked plastics include phenolic plastics, aminoplasts (such as urea-formaldehyde-melamine-formaldehyde, etc.).
Other cross-linked plastics include unsaturated polyesters, epoxy resins, phthalate diallyl resins, and the like.
(2) 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, etc. Thermosetting plastics are divided into two types: formaldehyde crosslinking type and other crosslinking type. After thermal processing, a cured product with insolubility is formed, and its resin molecules are crosslinked into a network structure by a linear structure. Further strengthening the heat will decompose and destroy. Typical thermosetting plastics are phenolic, epoxy, amino, unsaturated polyester, furan, poly silicon ether and other materials, as well as the newer poly phthalic acid two propylene ester plastic. They have the advantages of high heat resistance, heat deformation is not easy. The disadvantage is that the mechanical strength is generally not high, but the mechanical strength can be improved by adding fillers to make laminates or molded materials.
Thermosetting plastics made of phenolic resin as the main raw material, such as phenolic molded plastics (commonly known as bakelite), have the characteristics of durability, dimensional stability, resistance to other chemicals except strong alkali. Various fillers and additives can be added according to different uses and requirements. For varieties requiring high insulation performance, mica or glass fiber can be used as filler; for heat-resistant varieties, asbestos or other heat-resistant fillers can be used; for varieties requiring seismic resistance, various appropriate fibers or rubber can be used as fillers and some toughening agents to make high toughness materials. In addition, aniline, epoxy, polyvinyl chloride, polyamide, polyvinyl acetal and other modified phenolic resin can be used to meet the requirements of different applications. Phenolic resin can also be made into phenolic laminate, which is characterized by high mechanical strength, good electrical properties, corrosion resistance, easy processing, and is widely used in low-voltage electrical equipment.
Aminoplast has urea formaldehyde, melamine formaldehyde, urea melamine formaldehyde and so on. They have the advantages of hard texture, scratch resistance, colorless, translucent, etc., adding colorants can be made into colorful products, commonly known as electric jade. Because it is resistant to oil, not affected by weak alkali and organic solvents (but not acid), can be used for a long time at 70 ℃, short-term resistance to 110~120 ℃, can be used for electrical products. Melamine formaldehyde plastic has higher hardness than urea formaldehyde plastic, and has better water resistance, heat resistance and arc resistance, and can be used as arc resistant insulation material.
There are many varieties of thermosetting plastics made of epoxy resin as the main raw material, of which about 90% are based on bisphenol A epoxy resin. It has excellent adhesion, electrical insulation, heat resistance and chemical stability, small shrinkage and water absorption, good mechanical strength and so on.
Both unsaturated polyester and epoxy resin can be made into glass fiber reinforced plastic, which has excellent mechanical strength. Such as unsaturated polyester FRP, its good mechanical properties, low density (only steel 1/5 to 1/4, aluminum 1/2), easy to process into a variety of electrical parts. The electrical and mechanical properties of plastics made from diallyl phthalate resin are better than those of phenolic and amino thermosetting plastics. It has low moisture absorption, stable product size, good molding performance, acid and alkali resistance, boiling water and some organic solvents. Molding compounds are suitable for the manufacture of structurally complex, temperature-resistant and highly insulating parts. Generally, it can be used for a long time in the temperature range of -60~180 ℃, and the heat resistance grade can reach F grade to H grade, which is higher than that of phenolic resin and aminoplast.
Silicone plastics in the form of silicone ether structure are widely used in electronics and electrical technology. Silicone laminated plastics are mostly made of glass cloth as reinforcing materials; silicone molded plastics are mostly made of glass fiber and asbestos as fillers to manufacture high temperature, high frequency or submersible motors, electrical appliances, electronic equipment parts, etc. This type of plastic is characterized by a small dielectric constant and tg delta value, less affected by frequency, used in electrical and electronic industries, corona and arc resistance, even if the discharge caused by decomposition, the product is silicon dioxide rather than conductive carbon black. This type of material has outstanding heat resistance and can be used continuously at 250°C. The main disadvantages of polysiloxanes are low mechanical strength, low adhesiveness and poor oil resistance. Many modified silicone polymers, such as polyester-modified silicone plastics, have been developed for electrotechnical applications. Some plastics are both thermoplastic and thermosetting plastics. For example, polyvinyl chloride, generally thermoplastic, Japan has developed a new type of liquid polyvinyl chloride is thermosetting, the molding temperature is 60~140 ℃; the United States a called Lundex plastic, both thermoplastic processing characteristics, but also the physical properties of thermosetting plastics.
① Hydrocarbon plastics. It is a non-polar plastic with crystalline and non-crystalline. Crystalline hydrocarbon plastics include polyethylene, polypropylene, etc. Non-crystalline hydrocarbon plastics include polystyrene, etc.
② vinyl plastics containing polar genes. In addition to fluorine plastic, most of the non crystalline transparent body, including polyvinyl chloride, polytetrafluoroethylene, polyvinyl acetate and so on. Most of the vinyl monomers can be polymerized using a free radical type catalyst.
③ Thermoplastic engineering plastics. It mainly includes polyoxymethylene, polyamide, polycarbonate, ABS, polyphenylene ether, polyethylene terephthalate, polysulfone, polyethersulfone, polyimide, polyphenylene sulfide, etc. Teflon. Modified polypropylene and the like are also included in this range.
Thermoplastic cellulose plastics. It mainly includes cellulose acetate, cellulose acetate butyrate, cellol, cellophane and so on.
Classification of processing methods
According to the different molding methods of various plastics, it can be divided into many types, such as film pressing, lamination, injection, extrusion, blow molding, casting plastic and reaction injection plastic.
Film pressed plastics are mostly plastics with physical properties similar to those of general solid plastics. Laminated plastics refer to fiber fabrics impregnated with resin, which are laminated and hot pressed to form a whole material. Injection, extrusion and blow molding are mostly plastics with physical properties and processing properties similar to those of ordinary thermoplastics. Cast plastic refers to the condition that it can be used without pressure or with a little pressure, pour into the mold can be hardened into a certain shape of the liquid resin mixture, such as MC nylon; reaction injection plastic is the use of liquid raw materials, pressurized into the film cavity, so that the reaction solidified into a certain shape of products of plastic, such as polyurethane.
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