1, polyethylene (PE)
Polyethylene is a polymer of ethylene, is a thermoplastic, its industrial production methods, with high, medium and low pressure polymerization. Production methods, the molecular structure are very different performance in tandem with molecular structure to another.
Polyethylene is a white waxy solid, lighter than water, soft, water resistance and good resistance to cold, tasteless, non-toxic, heat resistance is poor, poor air tightness membrane, UV-sensitive. Easy to oxidation, aging, shrinking changed greatly, the printing performance is poor. According to their density. Can be divided into high-density, medium density, low density polyethylene and linear low density polyethylene.
2, polypropylene (PP)
Polypropylene is a byproduct of oil refining propylene when, after refining the propylene monomer, a catalyst in the catalyst under the polymerization reaction, and then separated from the polymer obtained. Molecular weight of 10 to 50 million, the density is very small, the smallest known plastic; non-toxic, tasteless, high transparency, mechanical properties, surface strength, frictional resistance, chemical resistance, moisture resistance are very good; at room temperature values above a large impact, but the low temperature impact resistance value is small; it easy to static electricity, poor printing performance. Polypropylene wide range of sources of raw materials, cheap, performance, and wide adaptability. Widely used in food industry. More used for manufacturing thin films, composite films with good transparency and surface gloss, the ability of the temperature of 120 degrees; can be made into boxes, blow into a plastic bottle, add some of the filler can be made of some machine parts and so on.
3, polystyrene (PS)
Polystyrene and benzene by ethylene in anhydrous alumina catalyst, the occurrence of ethyl benzene alkylation reaction, and then derived from styrene by catalytic dehydrogenation. Styrene monomer in the amount of initiator (benzoyl peroxide) and dispersant (polyvinyl alcohol) by heating the water suspension polymerization of polystyrene. Polystyrene is a colorless, transparent, non-ductile thermoplastics; non-toxic, tasteless, odorless, color is good, water vapor permeability than polyethylene, low moisture absorption, dimensional stability, good gloss; processing good performance and low cost; mechanical properties and increased with increasing molecular weight; heat resistance is low, can not be used in boiling water; low temperature, can withstand -40 ℃ low temperature; has good resistance to aging room; for alcohol organic solvents, mineral oil has better tolerance, acid and alkali can be also very good.
PS Because of superior performance, low cost, wide application, can be made into film, container, widely used in food industry; shrinkage rate of 60 to 70%, is the production of a good shrink packaging material with good insulation properties, can produce a variety of telecommunications components; also the production of machine parts, toys, daily necessities, etc.; in the addition of polystyrene foam, foam can be created, is a good cushion packaging materials.
4, polyvinyl chloride (PVC)
PEO is the role of vinyl chloride by the lead agent, the suspension polymerization or emulsion polymerization of vinyl chloride is generated. It was light brown, transparent, good toughness, density 1.4g/cm; has good chemical stability, can not easily be acid and alkali by corrosion; air tightness, water resistance, sealing properties, and printing is good, the production energy consumption low price; mechanical strength, wear and pressure are better than polyethylene and polypropylene. The main drawback is the poor thermal stability, heat is easy to decompose and release hydrogen chloride gas. As additives, such as plasticizers, stabilizers, and the number of different varieties, PVC can be made into different products, can produce hard products, such as tube, building materials, etc.; can produce artificial leather, wire and cable insulation, plastic floors. It is the most important role in the packaging is made of thin, soft membrane was divided, hard films, shrink film three. Sealing of soft soft membrane, suitable for high-frequency sealing station; tensile strength is very small, very high tear strength; sliding poor processing performance is also poor. Hard films, the tensile strength and tear strength are large, hard, elongation is small; water vapor permeability is small, good gas barrier, sliding better; printing adaptability, but to select the appropriate ink solvent; poor heat resistance, low temperature brittle. Shrink film transparency, and permeability of small, heat generated when the squeeze wide temperature range, shrinkage rate, and is a good shrink packaging materials. According to their production process can be divided into dry stretch. Tube stretching and longitudinal and transverse tensile and other varieties.
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