polyethylene (PE) is a thermoplastic resin produced by polymerization of ethylene. In industry, it also includes ethylene and a large number of alpha-olefin copolymers.      

Polyethylene odorless, non-toxic, feel like wax, with low temperature resistance, good chemical shaking, resistance to most acid and alkali corrosion. Insoluble in common solvent at room temperature, small water absorption, electrical insulation function.

Characteristics: polyethylene is a typical thermoplastic, odorless, tasteless, non-toxic combustible white powder. The PE resin processed by molding is a waxy granulated material with a milky white surface. Its molecular weight is in the range of 10,000 loa. The molecular weight of more than 100,000 is ultra-high molecular weight polyethylene f UHMWPE3. The higher the molecular weight, the better its physical and mechanical function, the closer to the required level of engineering materials. However, the higher the molecular weight, the more difficult it is to process.

The melting point of polyethylene is 10-- 130C. Low temperature resistance. It can still adhere to good mechanical function at 60 ° C, but the application temperature is 80~110 ° C. Polyethylene has good chemical instability, and can resist dilute nitric acid, dilute sulfuric acid and any concentration of hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, acetic acid, ammonia, amines, hydrogen peroxide, sodium hydroxide, potassium hydroxide and other solutions at room temperature. However, it is not resistant to strong oxidation corrosion, such as fuming sulfuric acid, concentrated nitric acid, chromic acid and sulfuric acid mixture.

At room temperature, the solvent will slowly corrode polyethylene, and at 90-- 100 ° C, concentrated sulfuric acid and concentrated nitric acid will quickly corrode polyethylene, causing it to destroy or decompose. Under the action of atmosphere, sunlight and oxygen, polyethylene will age, change color, crack, become brittle or powder, and lose its mechanical function.

At the molding processing temperature, it will also decrease its melt tolerance due to oxidation, discoloration and streaks, so it should be paid attention to in the molding processing and application process or material selection.

Because polyethylene has the above characteristics, it is easy to process and form, so the recycling of polyethylene has a very far-reaching value.

Nature:

1. Polyethylene has excellent chemical instability, resistance to hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, amines, sodium hydroxide, potassium hydroxide and other chemical substances at room temperature, nitric acid and sulfuric acid have a strong destructive effect on polyethylene;

2. Polyethylene is easy to photooxidation, thermal oxidation, ozone decomposition, easy to degrade under ultraviolet light, carbon black has excellent light shielding effect on polyethylene. After exposure to radiation, cross-linking, chain breaking, forming unsaturated groups and other reactions can occur.

A milky, translucent thermoplastic made from the homopolymerization of ethylene and copolymerization with a large number of alpha-olefin. Density 0.86~0.96g/cm3, according to the density of low density polyethylene (also including linear low density polyethylene), ultra-low density polyethylene and so on. Tasteless, non-toxic. Chemical resistant, insoluble in solvents at room temperature. Low temperature resistance, lower operating temperature -70~-100℃. Good electrical insulation, low water absorption.

Physical machine functions vary with density. Industrial low density polyethylene mainly uses high pressure (110~200MPa), high temperature (150~300℃) free radical polymerization. Others use high-pressure coordination polymerization, and sometimes the same set of devices can consume polyethylene commodities with a density of 0.87~0.96g/cm3, which is called the full density polyethylene process technology. Polyethylene can be processed into film, wire and cable sheath, pipe, all kinds of hollow products, injection products, fibers and so on. Widely used in agriculture, packaging, electrical and electronic, machinery, automobiles, daily necessities and other aspects.

There are a variety of classification methods, mainly by density classification:

① High-density polyethylene is an opaque white powder, milky white particles after granulation, the molecule is linear structure, little branching phenomenon, is a typical crystalline polymer. The function of the machine is better than low-density polyethylene, the melting point is higher than low-density polyethylene, about 126~136 ° C, and the embrittlement temperature is lower than low-density polyethylene, about -100~-140 ° C.

② Low-density polyethylene, is colorless, translucent particles, molecules with long branch chains, intermolecular display is not tight.

(3) Linear low-density polyethylene, the molecule generally only needs short branch chains, the machine function is between high density and low density polyethylene, the melting point is 15℃ higher than ordinary low density polyethylene, the low temperature resistance is also better than low density polyethylene, and the environmental stress cracking resistance is dozens of times higher than ordinary low density polyethylene.

In addition, according to the consumption method can be divided into high pressure polyethylene, medium pressure polyethylene and high pressure polyethylene, polyethylene consumption method is different, its density and melt index (indicating activity) is also different.

According to molecular weight can be divided into low molecular weight polyethylene, ordinary molecular weight polyethylene and ultra high molecular weight polyethylene.