Japanese producers continue to develop meteoric improvements in bioplastics for engineering applications. The newest is a stunner: NEC has developed a bioplastic that has better heat conductivity than stainless steel. The new material is aimed at new mobile phones and personal computers that are too small for fans and other devices used to remove heat. “In electronic product housings, the use of heat-conductive metals is considered to be one alternative to plastic for improving heat release,” NEC said in a statement. “However, heat conductivities in the thick direction of metal boards are too high and can cause partial or rapid increase in the temperature of housings near electronic parts that have high temperatures.”Previous attempts to use heat-conducting plastics for housings have been slowed by their high costs (due to 50 percent-plus content of fiber or stainless steel), poor moldability and high densities.
NEC has been researching alternatives using bioplastic, which has the same low heat conductivity as oil-based plastics. A new cross-linked structure between the resin matrix (polylactic acid) and carbon fiber is achieved through use of a new biomass binder. “This enables good heat conductivity in the plane direction of the PLA resin board, which is a characteristic conventionally difficult to attain in metal boards,” NEC said. A filling of 30% carbon fiber provides double the heat diffusion ability of stainless steel. NEC says it plans to begin mass production of the new composite in March, 2009, when it will seek new applications beyond housings of electronic products.
As reported by Design News, NEC has already developed bioplastics with kenaf reinforcement for mobile phone housings, a wall as shape memory bioplastics.
1.The biomass content of the new composite exceeds 90 percent, excluding the carbon fibers.
2.NEC says the new composite molds satisfactorily and has adequate strength for electronic products.