Friction and Wear Characteristics of Silicone-Modified Thermoplastics.

摘要

The use of plastic as a bearing material has increased greatly in the past decade. Advantages include freedom from maintenance, low cost, light weight, and quiet operation. Many products have used these advantages to achieve a maintenance free classification. Nylon, acetal and polytetrafluorocarbon (PTFE) have inherent properties which qualify them as self-lubricating. Lubricants have been added to these and other materials for many years, i.e. PTFE, MoS2 and graphite to decrease wear and friction and increase pressure-velocity limits (L.P.V.) . Fillers are also added to improve mechanical strength and dimensional stability. Highly filled, highly reinforced thermoplastics have been available for several years with LPV values of 20,000. An example is Nylon 66 with 30% glass and 15% PTFE. Although a LPV of 20,000 is suitable for many low load, low speed anplications, a LPV of 50,000 is required for plastics to compete with metals. Lubricants for plastics must be heat stable to withstand processing temperatures which often are as high as 600 deg F. They must also be compatible to some extent with the base resin to insure little or no migration and subsequent contamination of nearby parts and equipment. Lubricants, of course, should also have very low surface tension. jg p3.