Development of Low-Friction Elastomers for Stern-Tube Bearings

摘要

The objective of the program was to develop lubricant-filled nitrile rubber to obtain low friction and possibly low wear for seawater-lubricated sliding applications. Limited work has been done in industry on adding solid and/or liquid lubricants to the elastomers during compounding. Not much data have been published due to the proprietary nature of the work; but, based on what has been published and discussions with experts in the lubrication field, it is believed that no systematic study had previously been undertaken. This is probably the first systematic study to discover what has been done in the field and to further develop lubricant-filled elastomers. The base elastomer selected was butadiene acrylonitrile copolymer (per MIL-B-17901, Class I). Two lubricant approaches were taken. First, an incompatible and lubricating oil was added in the elastomer during compounding. As a result of aging, these oils migrate to the surface and continuously provide a lubricant film. In another approach, the solid lubricant particles were added during compounding. As the elastomer wears, it will expose newer solid-lubricant particles. The following solid lubricants were selected: MoS2, graphite, cadmium oxide-graphite-silver, and other proprietary additives. The fillers ranged in quantity from 5% to 20% by weight. The compositions were made by three experienced molders based on MTI's recommendations.