Shin Serizawa

Silicone derivatives as new flame retardants for aromatic thermoplastics used in electronic devices

New silicone derivatives that generate no toxic gas during combustion have been developed for use as flame retardants in the aromatic thermoplastics (polycarbonate and its derivatives, acrylonitrile–butadiene–styrene, polystyrene) used in many electronic devices. A special silicone with a branched chain structure, a phenyl-rich mixture of phenyl and methyl groups in the chain and methyl groups at the chain terminals was found to be effective in retarding the combustion of these plastics, and particularly so for polycarbonate (PC) and its derivatives. These silicone derivatives have shown themselves to be a perfect replacement for halogen compounds, which have been claimed to have a potential environmental hazard when the materials are subjected to combustion. Further, adding these silicone derivatives to PC does not adversely affect important other properties, such as strength, moldability and heat resistance; impact strength is in fact better than that of PC containing a bromine compound as a flame retardant.

Highly Functional Bioplastics (PLA compounds) Used for Electronic Products

We have developed highly functional bioplastics (biomass-based plastics), polylactic acid composites, which improve the environmental friendliness of electronic products. A kenaf-fiber-reinforced polylactic acid has high heat resistance, high impact strength, and good moldability, and its use in PC parts and mobile phone housing has started from September 2004 and May 2006 respectively. A thermoreversibly cross-linked polylactic acid has excellent shape memory and recyclability (i.e., rewritable shape memory), and was used to create freestyle (wearable) mobile products, shape of which users can easily adjust to their own preferences.

New environmentally conscious flame-retarding plastics for electronics products

Flame-retardant plastics containing no toxic flame-retarding additives such as halogen (bromine) compounds and phosphorus compounds have been developed for electronic products. A polycarbonate (PC) resin containing a silicone derivative as a new safer flame-retarding aromatic has been developed for use in housings. A special silicone with a branched chain structure and with an aromatic group in the chain was found to be greatly effective in retarding the combustion of PC resin. The PC resin containing the silicone shows other good properties, such as strength, moldability and heat resistance as well as high flame retardance and also good recyclability. Moreover, the authors have developed a new flame-retardant epoxy resin compound containing no flame-retarding additives as a molding resin for electronic parts. A self-extinguishing network structure of the epoxy resin compound was obtained by using an aromatic epoxy resin and a phenol derivative hardener; both of which have multi-aromatic groups in their main chain. The high flame retardance was achieved by the formation of a foam layer during combustion. The epoxy resin compound has other good properties (resistance to humidity, solder heating and thermal cycles, etc.) as well as high flame retardance and can be used as a high quality molding resin for LSIs.

Kenaf Fiber-Reinforced Biomass-Plastics Used for Electronic Products

The developed high-performance biomass-based plastics consist of polylactic acid (PLA) and fiber of kenaf, which fixates CO2 efficiently. Adding this fiber to PLA greatly increases its heat resistance and modulus and also enhances its crystallization. Eliminating the short particles from the kenaf fiber improves its effect on impact strength. Furthermore, adding a flexibilizer mainly made with biomass to the composite improves its strength. These composites (PLA/kenaf fiber, PLA/kenaf fiber/flexibilizer) show good practical characteristics as a housing material of electronic products, compared to petroleum-based plastics such as glass fiber-reinforced ABS resin