Common types of plastic are:
① Polyvinyl chloride (PVC)
It is the largest amount of plastic used in construction. The density of rigid polyvinyl chloride is
1.38 ～ 1.43g / cm3, high mechanical strength, good chemical stability, the use temperature range is generally between -15 ～ + 55 ℃, suitable for manufacturing plastic doors and windows, sewer pipes, wire trunking, etc.
② Polyethylene (PE)
Polyethylene plastics are mainly used for water supply and drainage pipes and sanitary ware in buildings.
③ Polypropylene (PP)
The density of polypropylene is the smallest of all plastics, about 0.90. Polypropylene is commonly used to produce construction products such as pipes and sanitary ware.
④ Polystyrene (PS)
Polystyrene is colorless and transparent glass-like plastic. Polystyrene is mainly used in the production of foam insulation materials, light-transmitting materials and other products in construction.
ABS plastic is a modified polystyrene plastic, consisting of three components based on acryl (A), butadiene (B) and styrene (S). ABS plastic can be used to make plastic decorative boards with patterns.
Polyethylene: Performance: Good electrical insulation, chemical resistance, cold resistance, non-toxic Use: Can be used to make food bags, pharmaceutical packaging materials, daily necessities, pipes, insulation materials, etc., the utensils are not stored for long periods of cooking oil, drinks Wait. Polyvinyl chloride: properties: resistance to organic solvents, chemical corrosion, abrasion resistance, good electrical insulation properties, good water resistance, additives are toxic to the human body. Uses: Can be used to make daily necessities, wire coverings, pipes, insulation materials
Materials, building materials, artificial leather, etc., the films made should not be used for packaging food. Polystyrene: Performance: good electrical insulation, good light transmission, water and chemical resistance, non-toxic. Uses: It can be used to make TV cases, automobiles, aircraft parts, toys, medical and health supplies, daily necessities, etc.
1 General varieties and classification of plastics
In daily life, most of the plastics we can directly touch or perceive are conventional general-purpose plastics, which mainly include five categories: PE, PP, ABS, PVC, PS. These five categories of plastics account for the vast majority of plastic raw materials , The rest can be classified into special plastic varieties, such as: PPS, PPO, PA, PC, POM, etc., their use in daily life products is very small, mainly used in engineering industry, defense technology and other high-end fields, such as Automotive, aerospace, construction, communications and other fields. According to their plasticity classification, plastics 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. , While most other plastics are opaque plastics. There are many different ways to classify plastics, which are not introduced here one by one.
2 properties and uses of commonly used plastics
① Polyethylene: Polyethylene is the highest-yield variety in the plastics industry. Polyethylene is an opaque or translucent, light-weight crystalline plastic with excellent low temperature resistance (minimum use temperature can reach -70 ~ -100 ° C), good electrical insulation and chemical stability.
Resistant to most acids and bases, but not heat resistant. Polyethylene is suitable for processing by injection molding, blow molding, and extrusion. Commonly used polyethylene can be divided into low pressure polyethylene (HDPE), high pressure polyethylene (LDPE) and linear high pressure polyethylene (LLDPE). Among the three, HDPE has better thermal, electrical, and mechanical properties, while LDPE and LLDPE have better flexibility, impact properties, and film-forming properties. LDPE and LLDPE are mainly used for packaging film, agricultural film, plastic modification, etc. HDPE is widely used in film, pipe, injection and daily necessities.
② Polypropylene: Polypropylene is a thermoplastic obtained by the polymerization of propylene. It is usually a colorless, translucent solid, odorless and non-toxic, with a density of 0.90 to 0.919 g / cm3. It is the lightest general-purpose plastic and has outstanding advantages. It has the characteristics of resistance to cooking in water, corrosion resistance, strength, rigidity and transparency are better than polyethylene. The disadvantages are poor low temperature impact resistance and easy aging, but it can be improved by modifying and adding additives. There are three types of polypropylene production methods: slurry method, liquid bulk method and gas phase method. Relatively speaking, polypropylene has more varieties, uses are more complex, and there are many fields. The varieties are mainly homopolypropylene and block copolymerization. Polypropylene and random copolymerized polypropylene. Depending on the application, homopolymerization is mainly used in the fields of drawing, fiber, injection, BOPP film, etc. Copolymerized polypropylene is mainly used in injection parts of household appliances, modified raw materials, daily injection products, Pipes, etc., random polypropylene is mainly used in transparent products, high-performance products, high-performance pipes and so on.
③ Polyvinyl chloride: Polyvinyl chloride is a plastic obtained by the polymerization of vinyl chloride. By adding a plasticizer, its hardness can be greatly changed. It is used for a wide range of hard and soft products. The production methods of polyvinyl chloride include suspension polymerization method, emulsion polymerization method and
The bulk polymerization method is mainly a suspension polymerization method. Because of its low cost and self-flame retardant properties, the product is widely used in the construction field, especially sewer pipes, plastic steel doors and windows, plates, artificial leather and other applications.
④ Polystyrene: General-purpose polystyrene is a polymer of styrene, which has a transparent appearance but has the disadvantage of being brittle. Therefore, polybutadiene can be added to make impact-resistant polystyrene (HTPS). The main production methods of polystyrene are bulk polymerization, suspension polymerization and solution polymerization. As a transparent raw material, when there is a need for transparency, it has a wide range of uses, such as automotive lampshades, daily transparent parts, transparent cups, cans, etc.
⑤ ABS: ABS resin is the product of the polymerization of three monomers of acrylonitrile-butadiene-styrene, referred to as ABS terpolymer. The properties of this plastic are also very different due to the different proportions of its components A (acrylonitrile), B (butadiene) and S (styrene) in the composition and the manufacturing methods. It is a kind of engineering plastic with a wide range of uses. It has outstanding physical and mechanical properties 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, fans, etc. Very large, and also widely used in plastic modification.
3 discrimination methods of common plastics
① Density method: check the density of various plastics, use liquid as the medium, check the plastic's ups and downs in the liquid medium, and roughly identify the major categories of plastics. (Due to the density of PVC> 1).
② Combustion method: mainly examines the color of the flame and the odor and smoke emitted during the combustion. Generally speaking, the burning flame of polyolefin raw materials is mostly blue or light blue, the smell is mild and light, and the smoke is white. After burning raw materials with benzene or chlorine, it is easy to emit black smoke and has a strong smell. In addition, PE, PP have dripping phenomenon, while PVC, etc. have no dripping, but have self-extinguishing phenomenon.
③ Optical method: mainly examine the transparency of the raw materials. The commonly used transparent raw materials are: PS, PC, PMMA, AS; translucent raw materials: PE, random copolymer PP, homopolymer PP, soft PVC, transparent ABS, etc., etc. The raw materials are essentially opaque.
④ Color discrimination method: Generally speaking, raw materials without additives, if they contain double bonds, the color will be slightly yellow, such as ABS, because of butadiene copolymerization, the polymer still contains double bonds after polymerization, so Will be slightly yellow.
Most other methods of identification require the use of various instruments, such as infrared spectroscopy, mass spectrometry, nuclear magnetic resonance, differential thermal scanning, and thermal analysis.
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