Polyethylene abrasion resistance

In the sheeting market, the low density polyethylenes are less important than the high density resins. The high density resins have excellent chemical resistance, stress-crack resistance, durabiUty, and low temperature properties which make them ideal for pond liners, waste treatment faciUties, and landfills. In thicker section, HMW-HDPE sheet makes good containers, trays, tmck-bed liners, disposable items, and concrete molds. The good durabiUty, abrasion resistance, and light weight are critical elements for its selection. 

The nylons have found steadily increasing application as plastics materials for speciality purposes where their toughness, rigidity, abrasion resistance, good hydrocarbon resistance and reasonable heat resistance are important. Because of their high cost they have not become general purpose materials such as polyethylene and polystyrene, which are about a third of the price of the nylons. 

Chlorosulphonated polyethylene rubber (Hypalon) has excellent chemical resistance even to oxidative acids at elevated temperatures. When specially compounded it can have excellent abrasion resistance in some operating conditions. 

Many polymer items are designed specifically to make contact with other materials. Where surface contact is concerned, two key properties are coefficient of friction and abrasion resistance. Polymers used in such applications include ultra high molecular weight polyethylene, polyacctal, fluorinated polymers, and natural and synthetic rubbers. Examples that we routinely come across include furniture upholstery, bushings and gears in office equipment, and bicycle tires. Industrial uses include the outer cover of electrical cables, and pipes that convey abrasive liquids such as slurries and powders. 

While chains having molecular weights of a few thousands only form brittle waxes, polyethylenes having molar masses of above hundred thousand show much better mechanical properties. They can be processed into films, pipes, and other performance products. When molar mass is further increased up to several millions, even higher impact strengths and abrasion resistances are achieved which enable these materials to be used in heavy-duty applications like skating floors and artificial hips. 

The polymer requires compounding with normal fillers to produce useful compounds. Chlorosulfonated polyethylene (CSM) excels in resistance to attack by oxygen, ozone, corrosive chemicals, and oil, and in addition has very good electrical properties. Electrical stability and resistance to corona and arc are good. The physical properties and abrasion resistance are also good. Light-colored goods made from CSM have excellent color-fastness. Due to the presence of chlorine atoms, this elastomer shows excellent flame resistance. 

Polyolefins. Ultra-High-Molecular-Weight Polyethylene.TIus is easily made by conventional low-pressure coordination polymerization. Hercules Hi-fax 1900 has a molecular weight of 2.5-5.0 million. Its outstanding properties are low coefficient of friction (0.11) abrasion-resistance superior to nylon, polyurethane, and steel unbreakable in the Izod notched impact test and high resistance to most inorganic and many organic chemicals. 

A comparison of the abrasive wear by Bohm (1990) found that the hard and more brittle plastics, such as polyacetals, polyamide-imide, and polycarbonates, are less abrasion resistant than softer and tougher materials such as the polyethylenes and polyurethanes. Table 7.2 details some comparative... 

Nonionic polyethylene softeners and lubricants. Improve abrasion resistance while imparting excellent fabric softness and sewability. 

Modified cationic polyethylene emulsion softener produces softness, bulk, abrasion resistance, and needle lubricity on cotton and knitted and woven fabrics. 

A polyethylene emulsion that improves sewing characteristics, tear strength, and abrasion resistance of textile fabrics. 

MYKON HD emulsion provides excellent sewing properties while imparting a soft hand to treated fabrics—unlike the waxy hand of other high density polyethylene products. MYKON HD softener also improves tear strength and abrasion resistance of treated fabric. 

Other important products include radiation cross-linked foamed polyethylene which is used for thermal insulation, floor mats, crash padding, floating jackets, and wood/plastic composites cured by gamma irradiation. These have been used successfully for flooring in places such as department stores, airports, hotels, and churches where their excellent abrasion resistance, the beauty of the natural grain, and low maintenance costs are important. This latter technique is also being used in the conservation of objects made of stone and wood of interest to our cultural heritage. 

Composite Particles, Inc. developed two methods of surface modification of polymeric materials which are used for materials of different shapes and compositions. Here, only the spherical, non-rubber particles are discussed. Further information is included in the section on rubber particles below. One method of surface modification is based on exposing the polymeric powder to a chemically reactive gas atmosphere which oxidizes surface groups to form OH and COOH functionalities. These functionalities are then available for reaction with the components of the matrix into which modified particles are introduced. Vistamer HD and UH are manufactured by this method from polyethylenes of different molecular weights. Two factors can be regulated here the properties of the core particle and the type and density of functional groups on the surface of these particles. Polyethylene is a material, which without this modification, will not be compatible with most systems. The surface modification allows the incorporation of the material into resins. This improves abrasion resistance, tear strength, and moisture barrier properties and reduces the fiiction coefficient. 

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