SKF Selects VICTREX® PEEK(TM) Polymer for High Performance Bearing Cages for the Automotive Industry
West Conshohocken, PA - (February 7, 2008) - In order to meet the most demanding automotive applications, SKF Group, a leading manufacturer of roller bearings, chose high performance VICTREX® PEEK(TM) polymer for the cage design of its deep groove ball bearings that are used where high speed, chemical attack or high temperature conditions occur such as in alternators and transmissions.
VICTREX PEEK polymer was chosen for the cages because of its superior combination of strength and flexibility, high operating temperatures, high chemical and wear resistance, and ease of processing. The design of the cage and material used are of paramount importance for the performance of the cage as well as for the operational reliability of the bearing itself.
Cages are mechanically stressed by friction, strain and inertia. They may also be subjected to the chemical action of certain lubricants, lubricant additives or products of their ageing, organic solvents or coolants. The relative importance of these considerations can be affected by other operational parameters such as elevated temperatures, shock loads, vibrations or combinations of these and other conditions. The materials from which the bearing components are made determine to a large extent the performance and reliability of the rolling bearings. According to SKF this is the reason it developed cage types based on VICTREX PEEK polymer and designed them for the highest requirements of the automotive industry.
Polymer cages have an excellent combination of strength and elasticity. The good sliding properties of the polymer on lubricated steel surfaces and the smoothness of the cage surfaces in contact with the rolling elements produce just little friction so that heat generation and wear in the bearing are at a minimum. The low density of the material means that the inertia of the cage is small. The excellent running properties of polymer cages under lubricant starvation conditions permit continued operation of the bearing for some time without risk of seizure and secondary damage.
While polymer cages exhibit excellent strength and elasticity, these properties are temperature dependent and are subject to permanent changes under operating conditions called aging. The most important factors that play a role in aging behavior are temperature, time and the medium (lubricant) to which the polymer is exposed. According to SKF, when nylon 6/6, the most commonly injection molded cage material, is used, it appears that the cage life decreases with increasing temperature and the aggressiveness of the lubricant. And some media are even so aggressive, that cages made from glass fiber reinforced nylon 6/6 should not be used at operating temperatures above 70°C (158°F). In contrast, VICTREX PEEK polymer shows no signs of aging by temperature and oil additives up to +200 °C (392°F).
In addition to using VICTREX PEEK polymer for the cages of the deep groove roller bearings, SKF also uses the polymer for the cages of ball and cylindrical roller bearings, such as hybrid or high-precision bearings, as well as for some dedicated automotive customer variants.
Victrex USA, Inc., a division of Victrex plc, is the sole manufacturer and supplier of VICTREX PEEK polymer worldwide. For more information, please call (800) VICTREX or visit the Victrex website at www.victrex.com or victrex.mobi.
