All about high molecular weight polyethylene

High molecular weight polyethylene (PE-500) is a plastic polymer. It possesses a number of unique physical and chemical properties, due to which it can be used in extreme conditions. In this article, we will consider everything about high molecular weight polyethylene.

This material belongs to one of the types of plastic polymerized ethylene. Its feature is elongated linear molecular bonds oriented in the same direction. Such circuits are distinguished by better perception and transfer of loads.

In appearance, high molecular weight polyethylene resembles plastic. It is solid, odorless, and contains no toxic substances. The material is produced by the synthesis of ethylene and metallocene catalysts in low-pressure plants. At the production stage, a color is added to the raw materials to give the polymerized ethylene color.

Manufacturers also produce an ultra-high molecular weight (ultra-high molecular weight) polymer with a molecular weight of more than 10,000,000 units. (PE-1000). In terms of strength characteristics, it is several times superior to some grades of carbon and stainless steels.

The material has a number of significant advantages. The main advantages are as follows:

• excellent resistance to wear and mechanical abrasion; high density polymer has high impact resistance;
• resistance to cracks, chips and other types of deformation;
• resistance to temperature fluctuations, due to which the material is allowed to operate both at excessively high and at minimum temperature indicators;
• resistance to moisture and aggressive substances (except for oxidants); this feature is achieved due to the absence of amides, esters or hydroxyl groups in the material, which are susceptible to chemically aggressive substances;
• resistance to solar radiation;
• high hygienic properties - the material is not susceptible to attacks by pathogenic microorganisms; fungus and mold do not form on it;
• good electrical insulating and dielectric ability;
• PE-500 polyethylene has excellent weldability;
• radiation resistance.

High molecular weight polyethylene is relatively new. It is produced by 2 domestic enterprises (Tomskneftekhim and Kazanorgsintez). Manufacturing technology is complex and costly, which affects the cost of the finished product.

High-strength polyethylene has long molecular chains that are almost parallel to each other. This structural feature provides high strength indicators. However, weak bonds arise between some molecules, which is why the material cannot be called heat-resistant. Its operating temperatures are up to + 100 ° С. With an increase in temperature indicators to +140 degrees, the polymer melts and turns into a viscous mass.

Polymer PE-1000 has the following technical characteristics:

• water absorption - 0.01-0.05%;
• specific gravity - 0.93-0.94 g / cm³;
• flexural modulus - no more than 1 GPa;
• the coefficient of friction is about 0.1;
• impact strength coefficient - 160-170 kJ / m²;
• bending elongation - 8-10%;
• surface resistance - 1014 ohms.

High molecular weight polyethylene is manufactured according to standards corresponding to GOST 16338-85. The production uses the method of ethylene synthesis under the influence of metallocene catalysts. At the moment, there are several known methods of polymer processing.

Thanks to these methods, large-format monolithic polyethylene, plates and cylinders are obtained. In the process of further machining, planed strips and various mechanisms for equipment are obtained from them. The production technology implies cold pressing of the polymer powder into blanks and their subsequent sintering at a temperature of +200 degrees. As a result of heat treatment, semi-finished products are obtained - monoliths, plates and blocks.

The production process consists in melting the feedstock at high temperatures to a homogeneous rubbery mass. From it, using special units with nozzles, rods, pipes or tapes of various lengths are squeezed out.

The manufacturing technology includes several stages: dissolving the feedstock in paraffin oil and forcing the resulting mass through thin holes into water. As a result, yarns are obtained, which are further fired in furnace equipment with simultaneous drawing of fibers and removal of solvent substances. When processed by gel spinning, a super-strong fiber is obtained.

Due to its unique properties, high molecular weight polyethylene is used in various fields. It is often used as an analogue, replacing various non-ferrous metals, high-alloy steels and other materials.

The ultra-strong polymer has been used for the manufacture of implants since 1962. Today, it is used to make prostheses for hip joints in surgery and dental implants in dentistry. The material is used to create various orthopedic products.

The material is used for the manufacture of equipment and components for food production, containers for storage and transportation of chemically aggressive substances, bottles for cosmetics, barrels, tanks.

Strong polymer fibers are used to make personal protective equipment for security personnel. In particular, bulletproof vests and helmets are made of them. The resulting armor is lightweight, but at the same time it reliably protects against bullet wounds. And also with the help of this polymer, special equipment is armored.

High-strength polyethylene is used for the manufacture of parts operating in hydraulic or oil environments. It is used to produce bearings, bushings, bushings, gears - parts subject to a high degree of mechanical abrasion. Spare parts for pneumatic installations with increased working pressure are made of heavy-duty polymer PE-1000.

The material is used in the manufacture of fencing suits, mountaineering uniforms, skis, snowboards.

Numerous consumer goods are made from high-strength polymer. These include floriculture and bathroom furnishings, household items and garden tools. It is used for the production of furniture, children's toys, mobile toilets, and equipment for arranging children's playgrounds.

You can learn even more useful information about high molecular weight polyethylene from the video.