An Acrylic Rubber Modified Phenolic Resin Which Has Good Flexibility at Low Temperature 2008-01-2539
Phenolic resins have been widely used as a binder for friction materials such as disk pads and brake linings.
Brake noise has been one of the key requirements and outstanding issues in brake manufacturer, especially the study of and elimination of brake noise at low temperatures.
In an effort to reduce brake noise, we have traditionally developed elastomer modified phenolic resins, which give good flexibility to disk pads. A typical elastomer is an acrylic rubber (AR) that is very effective in reducing brake noise. A general AR gives good flexibility to the phenolic resin at room temperature but the flexibility decreases at low temperatures. The reason is that the physical properties such as hardness and viscoelasticity change at the glass transition temperature (Tg) of an elastomer and Tg of the general AR modified resin is around 0°C. Therefore, it is difficult to reduce the brake noise at low temperature using a general AR.
In this study, we have developed a phenolic resin that has excellent flexibility under a wider range of temperature, especially below freezing point. This was achieved by developing an acrylic rubber modified phenolic resin that was able to keep excellent flexibility below freezing point and had Tg of approximately -30°C. This newly developed resin is equivalent to a general AR modified resin for heat resistance and flexibility at room temperature, too. As a result the new AR modified phenolic resin is able to contribute to the reduction of brake noise at a much wider temperature range.