SDK Develops Technology To Directly Join/Bond Aluminum Alloys And Polycarbonate Resin

Showa Denko (SDK) has developed an innovative technology to directly join/bond aluminum alloys and polycarbonate resin—a commodity amorphous engineering plastic—without using an adhesive.

It is common to join/bond aluminum alloys and polycarbonate resin through mechanical joining (using bolts, and the like) or adhesive bonding (using an adhesive). In recent years, much attention is focused on new technologies that directly join/bond resin materials—at the time of injection molding—to metallic materials. These new technologies are expected to simplify process, increase productivity, and enable processing into complicated shapes. In many cases, however, they depend on mechanical bonding power, such as an anchor effect resulting from injection of resin into roughened metal surface. Thus, it was believed that polycarbonate resin (and other amorphous engineering plastics) would not be suitable for joining/bonding metallic materials by conventional methods.

SDK has enabled such direct joining/bonding based on its expertise in aluminum alloys and polymer chemistry gained over many years. Specifically, SDK has developed an innovative joining/bonding technology based on special surface treatment and primer treatment for aluminum alloys, realizing chemical bonding power ^Note1 in addition to the anchor effect. Our experiments show that the new technology can be used under ordinary polycarbonate molding conditions, providing sufficient bond strength of more than 25MPa (mega pascal) ^{Note 2}. There is no need for special conditions or equipment in securing sufficient bond strength.

As this technology enables direct joining/bonding of commodity polycarbonate resin and light-weight aluminum, it is applicable to the housing of smartphones. SDK will continue development work to optimize its aluminum-surface-treatment technology and primer-coating conditions, thereby increasing bond strength and durability. In the future, SDK will aim to use the technology in the area of super-engineering plastics with higher heat resistance for automotive parts applications.

In its medium-term business plan “The TOP 2021,” SDK is promoting cooperation among various business segments and strengthening marketing functions. The automobile and electronic device industries have an increasing need for diversified and sophisticated materials that are light in weight and with improved characteristics regarding heat dissipation, heat accumulation, and insulation. In view of such market needs, SDK is working to develop compound materials by combining its own diversified technologies. The development of the metal/resin direct joining/bonding technology announced today is one of the examples of such efforts. We will continue creating new solutions by deepening and combining technologies from our wide-ranging businesses and products.

¹.This technology employs “covalent bonding” as part of its bonding mechanism. “Covalent bonding” represents the strongest bonding power among various types of chemical bonding, and is considered to be about 100 times as powerful as intermolecular force.

².The numerical value of “25MPa” was obtained as a result of tension shear tests (ISO 19095).