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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. 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.

The automotive industry has increasingly been focusing its efforts on vehicle part weight reduction, with the aim of improving fuel efficiency as an environmental protection measure. As part of these efforts, the industry has actively been developing plastic pulleys to replace conventional steel pulleys. Of the various pulleys used in vehicles, the air conditioner (A/C) compressor pulley is exposed to the harshest working environment. We therefore investigated towards development of a plastic pulley for A/C compressor application. Required material properties were first identified on the basis of required product characteristic values. As a result, a phenolic resin material was developed that is superior in heat resistance one of the most important properties among those identified. Using the material, we succeeded in developing an A/C compressor plastic pulley, achieving approximately 50% weight reduction compared to conventional steel pulleys.

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.

Recently, in view of environment, safety, comfort and convenience for cars, the demand of low fuel consumption is increasing more than before, and weight saving of the automotive parts is pursued. In the tide of weight saving, there is a strong demand of light weightening of the backing plate by replacing steel with plastics. We have been developing long fiber phenolic molding compound, which has excellent mechanical strength and excellent heat resistance, and have examined in order to apply it to the backing plate for brake pad. By applying this material to backing plate, the weight of brake pad can be reduced in half compared with that of conventional pad made of steel. In the automotive parts, it is said that reduction of part weight under the suspension is about ten times as effective for reducing fuel consumption as that of weight upper the suspension, therefore, phenolic brake pad has a big impact.