A new approach to “outsert” molding treats a piece of metal so that resin can be molded directly onto it and adhere strongly to one surface without requiring either holes punched in the metal or encapsulation by the plastic. The process, called Nano-Molding Technology (NMT), was developed by Taiseiplas Co., Ltd. in Tokyo, Japan, and is available for license. The company also uses the process itself to mold custom parts, says Kogoro Osumi, director.
NMT at present works only with aluminum and resins that contain ester linkages, such as PBT and PPS. These resins also must be compounded with 20% to 40% glass or carbon fibers in order to match the linear expansion coefficient of the aluminum.
For NMT, aluminum sheet is dipped into an alkaline solution and then into an acid solution to remove oxides and grease from the surface. The aluminum is then dipped into a proprietary amine solution, which etches microscopic holes 20 to 30 nanometers deep and wide. A coating of the amine remains on the aluminum surface and forms an exothermic reaction with the resin, generating heat to keep the resin sufficiently fluid to enter the tiny holes, which would not otherwise occur. A strong mechanical bond forms when the melt cools. Taiseiplas guarantees a tensile tear strength of 200 to 300 kgf/cm2 and a pull-off breaking strength of 90 to 100 kgf/cm2. Tests show the resin fails before the metal/plastic bond does.
NMT is being used commercially to produce remote-control units for Sony. Other initial targets are electronic and automotive applications such as notebook computer housings, automotive electronic controls, and auto interior parts. Tel: +81 3 3243 1851 • www.taiseiplas.com