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Key requirements for disk pads include flexibility, heat resistance, and low wear. The traditional approach for improving the flexibility of a phenolic resin has been to modify the resin using an elastomer. Elastomer modified phenolic resins exhibit difficulties in disk pad applications. The thermal decomposition temperature of most elastomers is lower than that of an unmodified phenolic resin. Thus, modifying a phenolic resin with an elastomer reduces its heat stability. In addition, the glass transition temperature of a rubber-modified resin such as acrylic rubber is around 0° C. The physical properties, such as hardness and viscoelasticity, change at the glass transition temperature. This change affects the friction properties of the disk pad. Unmodified resins have high glass transition temperatures and therefore exhibit stable performance characteristics. In this study, we tried to obtain flexibility in an unmodified phenolic resin in order to maintain heat resistance.

Phenolic resins have been widely used as a binder for friction materials such as disk pads and brake linings. Requirements for disk pads are flexibility, heat resistance, low wear and so on. To solve the above requirements, we have developed various modified resins. At the same time, reduction of manufacturing cost is also required to maintain price competitiveness. The way to reduce manufacturing costs is to cut down the molding cycles and post-baking time, as well as use raw materials with a low price. To increase the molding temperature is one of the effective methods for reducing molding cycle, because the reactivity of phenolic resin increases. However, it is much more difficult to determine the gas release time because large amounts of gas evolve in a very short period of time. The phenol-hexamine curing system is limited in its ability to reduce the molding cycle. In this study we developed a gas-free resin system.