Wear-resistant additives glass fiber reinforcement

Aromatic polyamide fiber, commonly known as aramid liber or Kevlar , is one of the latest wear-resistant additives to be used in thermoplastic composites. Unlike the traditional fiber reinforcements of glass and carbon, aramid is the softest and least abrasive fiber. This is a major advantage in wear applications, particularly if the mating surface is sensitive to abrasion. 

Nowadays, in place of asbestos, fibrous reinforcements are used that include glass fiber, steel fiber, aramid fiber, potassium titanate fiber, etc. Since these fibrous reinforcements have their own specific properties, in practice, a mixture of them is used. Potassium titanate fiber is a hard inorganic fiber. It can improve the strength, the heat resistance and the wear resistance of the fiietion material. In addition, it can enhance the friction coefficient of the friction material through its abrasive property. 

The incorporation of 30% of glass fiber into polyphenylene oxide brings about a relatively small increase in tensile strength from between 50 and 65 MPa for the unreinforced polymer to 85 MPa in the reinforced polymer (Table 3.1). The addition of glass fiber is accompanied by an increase in flexural modulus from 2.5 to 17.2 GPa (Table 3.2) and a dramatic decrease in modulus of elasticity from between 20 and 60% down to 1% (Table 3.4). The incorporation of glass fibers into polyphenylene oxide produces a distinct improvement in the wear resistance of the reinforced polymer accompanied by small improvements in fatigue index [19] and the coefficient of friction [20]. 

Materials used such as stifFer plastics can reduce hysteresis heating. Crystalline TPs for example (the popularly used acetal and nylon) can be stiffened by 25 to 50% with the addition of fillers and reinforcements. Others used include ABS, polycarbonates, polysulfones, phenylene oxides, polyurethanes, and thermoplastic polyesters. Additives, fillers, and reinforcements are used in plastics gears to meet different performance requirements (Chapter 1), Examples include glass fiber for added strength, and fibers, beads, and powders for reduced thermal expansion and improved dimensional stability. Other materials, such as molybdenum disulfide, polytetrafluoroethylene (PTFE), and silicones, may be added as lubricants to improve wear resistance. 

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