High-Ortho Phenolic Resin for Improved Flexibility 2007-01-3943
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. The result was the development of a high-ortho phenolic resin. We found that the amount of ortho linkages in the phenolic resin is related to its flexibility. The amount of ortho linkages also affects the curing properties and cross-linking structure of the polymer.