Polyethylene (PE)

日期:2019/12/2 8:47:35 / 阅读: / 来源:本站



The first section. Polyethylene (PE)

Chapter II Properties and Uses of Packaging Plastics

Polyethylene is a type of thermoplastic that has the largest production and consumption among plastics. Its main use is for the production of various packaging materials. Therefore, polyethylene is the most widely used variety in plastic packaging.

Polyethylene is divided into low density, medium density and high density according to density; it can be divided into homopolymer and copolymer according to polymer monomer component. Homopolymers or copolymers with different densities and different ethylene have good compatibility, and can be modified by blending with each other. Polyethylene can also add inorganic fillers and foaming agents to produce various cushioning packaging materials, and adding flame retardants and antistatic agents can also produce various antistatic electromagnetic shielding packaging materials. H

The performance of homopolyethylene depends on the relative molecular mass, relative molecular mass distribution, crystallinity, length and number of branches on the main chain. The melt flow rate and density are used in actual production to predetermine the general range of its performance. The performance of the polyethylene copolymer depends on the properties of the comonomer, the content of the comonomer, and its structural morphology. 1

Low-density polyethylene

In 1939, low-density polyethylene (LDPE) was first industrially produced by the British company ICI, and its production growth rate reached 20% in the 1960s. The average growth rate of 5% to 8% in the 1970s to this year is the most developed in polyethylene. Fast,

Its manufacturing method is 99.999% high-purity ethylene in a tube or kettle reactor under a pressure of 250 to 300 MPa,

Polymerized under an organic peroxide catalyst at a temperature of about 120 ° C. LDPE can be molded by injection, extrusion, blow compression, powder molding (including rotary molding), welding and other processing methods.

1.LDPE basic characteristics

Low density polyethylene has the following characteristics:

①The relative density is 0.915 ~ 0.925, and the relative molecular mass is 100,000 ~ 500,000. It is a crystalline polymer with high

Crystallinity;

② Appearance is milky white, translucent, non-toxic, slightly waxy solid particles;

③ Low mechanical strength, good softness, elongation, and low surface hardness;

④ Low temperature resistance, embrittlement temperature can reach -70 ℃, good impact resistance at low temperature;

⑤ Low water absorption, excellent moisture resistance and excellent chemical resistance;

⑥ Excellent electrical insulation, up to 24.4mV / pm;

⑦Easy to burn, colorless and smokeless with waxy smell and burning dripping phenomenon during burning, not easy to bond and print

③ Aging by sunlight and heat (100 ℃);

⑨ Resistant to various strengths of salt and alkali solutions, 50% sulfuric acid, 40% nitric acid and concentrated hydrochloric acid

Organic solvents;



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