Bioplastic composite to make heatsinking packages

Innovative bioplastic has potential to make electronic products more environmentally sound, while solving conventional heat release issues.

NEC Corp has developed an all-new kind of bioplastic composed of plant-based material and carbon fibre, which achieves heat conductivity higher than that of stainless steel.

The innovative bioplastic is expected to make electronic products more environmentally sound, while solving conventional heat release issues.

The cross-linked structure of carbon fibre through use of a unique binder in the polylactic acid (PLA) resin achieves high heat diffusion (with 10% and 30% carbon fibre the heat diffusion ability of the new bioplastic composite is comparable to and double that of stainless steel, respectively).

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.

The composite is extremely environmentally friendly as it is mainly composed of biomass-based components including the binder (the biomass ratio exceeds 90%, excluding inorganic components such as the carbon fibre).

The strength and mouldability of the composite have been fundamentally verified for use in electronic products.

The application of the bioplastic composite in the housings of electronic products will easily release the heat generated from high temperature electronic components through the entire housing surface, while reducing increases in the temperature of nearby components.

Recently, small-sized electronic products such as mobile phones and personal computers have suffered heat-release issues due to an increase in the amount of heat being generated from electronic parts.

However, conventional heat-release devices such as fans and sheets are difficult to incorporate as products become smaller and slimmer.

In electronic product housings, the use of heat-conductive metals is considered to be one alternative to plastic for improving heat release, however, heat conductivities in the thickness direction of metal boards are too high and can cause partial or rapid increase in the temperatures of housings near electronic parts that have high temperatures, causing unnecessary anxiety to the user.

Attempts have been made to increase heat release from whole parts of housings by using heat-conductive plastics.

However, previous heat-conductive plastics have had the disadvantages of low mouldability, as well as high densities and costs, as they contain large amounts (more than 50%) of heat-conductive fillers such as fibres or particles made from carbon and metals.

Therefore, a new kind of heat-conductive material has been long sought after to solve these issues.

On the other hand, bioplastics made from renewable plant resources, including PLA, have been enjoying increasing attention as new environmentally friendly materials and are now starting to be used in electronic products.

But, PLA has low heat conductivity like current petroleum-based plastics and many of its practical characteristics are also lower than those of petroleum-based plastics.

NEC has been focusing its research activities on how to solve these bioplastic issues and has succeeded in the development of a kenaf fibre-reinforced PLA composite that realises high heat resistance and strength.

Moreover, the composite is already being used in a mobile phone commercialised by NEC.

In addition, NEC has also discovered how to add flame retardancy - without using toxic flame retardants - and shape memory to PLA.

The new bioplastic that achieves high heat conductivity has been enabled by new technology for carbon-fibre cross-linking with a unique biomass-based binder, which were both realised at NEC's fundamental and environmental research laboratories.

NEC will continue to develop these technologies toward realisation of mass production of the bioplastic composite by the end of the fiscal year ending March 2009, after which it will start to use the composite in housings of electronic products and seek out new applications.

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