POLY(ETHYLENE)

Химические свойства

light yellow waxy solid

Использование

POLY(ETHYLENE) can be used for rubber hose;electric wire and cable;special synthetic rubber;wires and cables.

Подготовка

In the preparation of chlorosulphonated polyethylene the polymer (commonly, a low density polyethylene with molecular weight (Mn) of about 20000) is treated with chlorine in the presence of a small amount of sulphur dioxide. Typically, the reaction is carried out in solution in hot carbon tetrachloride. Both chloride and sulphonyl chloride groups are introduced into the polymer, the degree of substitution and the ratio of the two types of groups depending on the reaction conditions. Commercial products generally contain about 30% chlorine and 1.5% sulphur, which corresponds to approximately one chlorine group per 7 carbon atoms and one sulphonyl chloride group per 85 carbon atoms. Such a product may be represented as follows:

The reaction probably proceeds by the following radical mechanism:

Методы производства

This type of elastomer is made by dissolving polyethylene in carbon tetrachloride and then treating it with chlorine and sulfonyl chloride in the presence of a catalyst. After the desired degree of chlorosulfonation has been attained, the residual chlorine–sulfur dioxide mixture is stripped off, a stabilizer is added, and the commercial product is isolated as raw rubber in crumb or film form.

Промышленное использование

This material, more commonly known as Hypalon,can be compounded to have an excellentcombination of properties including virtuallytotal resistance to ozone and excellent resistanceto abrasion, weather, heat, flame, oxidizingchemicals, and crack growth. In addition,the material has low moisture absorption, gooddielectric properties, and can be made in a widerange of colors because it does not require carbonblack for reinforcement. Resistance to oilis similar to that of neoprene. Low-temperatureflexibility is fair at –40°C.
The material is made by reacting polyethylenewith chlorine and SO2 to yield chlorosulfonatedpolyethylene. The reaction changes thethermoplastic polyethylene into a synthetic elastomerthat can be compounded and vulcanized.The basic polyethylene contributes chemicalinertness, resistance to damage by moisture, andgood dielectric strength. Inclusion of chlorinein the polymer increases its resistance to flame(makes it self-extinguishing) and contributes toits oil and weather resistance.