Compatibility of Silicone-Base Brake Fluids with Automotive Vehicle Elastomers

An investigation was conducted to determine the compatibility of recently specified silicone brake fluids with elastomers expected to be found in vehicles submitted to the US Army for test and evaluation to compare their performance with conventional fluids. More than 1500 immersion tests were conducted at temperatures ranging from 0°F to 248°F (-18 to +120°C) with 14 different elastomers and 5 different brake fluids. It was found that the silicone brake fluids performed as well as/or better than the conventional fluid in all tests involving vehicle brake system elastomers. Brake performance of systems in which silicone brake fluids and conventional brake fluid become mixed will operate normally with no fluid/elastomer related problems. Contaminants such as petroleum based fluids will cause undesirable attacks on brake system elastomers regardless of the fluid in the system.