Abrasion resistance friction

Chapters 1-4 of the book deal with the mechanical, electrical and thermal properties of a wide range of unreinforced and reinforced engineering plastics. Chapter 5 discusses various miscellaneous properties such as wear, abrasion resistance, frictional hardness properties, surface properties and weathering, and chemical resistance. In addition, this chapter covers a particular property of food packaging plastics, namely their gas barrier properties. 

The fabric may also be given one or more of a number of other finishing treatments, either ia tandem with web formation and bonding or off-line as a separate operation, as a means of enhancing fabric performance or aesthetic properties. Performance properties iaclude functional characteristics such as moisture transport, absorbency, or repeUency flame retardancy electrical conductivity or static propensity abrasion resistance and frictional behavior. Aesthetic properties iaclude appearance, surface texture, and smell. 

The resins can be a novolak—hexa or a resole—novolak blend. In some appHcations Hquid resoles are used. Addition of alkylated phenol, oil, or cashew nutsheU Hquid (CNSL) reduces hardness and increases abrasion resistance. Modification by mbber improves the coefficient of friction and reduces brake fading. 

Two mote piopeities for which nylon shows paiticulai advantages are abrasion resistance and coefficient of friction. These properties make the material suitable for use in, for example, unlubricated beatings and intermeshing gears nylon has been used in such apphcations from an eady stage in its development. 

Composite Plating. An electroless nickel matrix can be used to securely bond diamonds to cutting tools, and electroless nickel—diamond composites are also used (see Tool materials). The NYE-CARB process gives a siUcon carbide—electroless nickel composite that has extremely high abrasion resistance (49). Electroless nickel—Teflon composites are being promoted as low friction materials. 

The films are generally dark in colour and often show a fine network of cracks due to differential expansion of oxide and metal on warming to ambient temperature. They are generally left unsealed, since sealing markedly reduces abrasion resistance, but may be impregnated with silicone oils to improve the frictional properties. Applications include movable instrument parts, pump bodies and plungers, and textile bobbins. 

A different type of low friction or low drag application is encountered with sliding doors or conveyor belts sliding on support surfaces. In applications like this the normal forces are generally quite small and the friction load problems are of the sticking variety. Some plastics exhibit excellent track surfaces for this type of application. TFEs have the lowest coefficient of any solid material and represent one of the most slippery surfaces known. The major problem with TFE is that its abrasion resistance is low so that most of the applications utilize filled compositions with ceramic filler materials to improve the abrasion resistance. 

Dekempeneer, E., Van Acker, K., Vercammen, K., Meneve, J., Neerinck, D., Eufinger, S., Pappaert, W., Sercu, M., and Smeets, J., Abrasion Resistant Low Friction Diamond-Like Multilayers," Surface and Coatings Technology, Vol. 142-144,2001,pp. 669-673. 

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. 

Most polybutadiene is used in tyre applications, and the majority of this use is in blends with other polymers, such as NR and SBR, where polybutadiene reduces heat build-up and improves the abrasion resistance of the blend. The friction on ice of winter tyres is also improved by using higher levels of polybutadiene in the tread blend. 

Abrasion can be defined as the loss of material from a surface due to frictional forces and is most often the result of two surfaces being rubbed together. Abrasion resistance is then the resistance to wear resulting from mechanical action on the surface. 

Abrasion is the wearing away of a materials surface by friction. The most widely used tests to measure abrasion resistance employs Williams, Lamborn, and Tabor abraders (ASTM D-1044). In each test the abrader is rubbed on the material s surface and the material loss is noted. 

Friction, hardness, and abrasion resistance are related closely to the viscoelastic properties of polymers. 

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