| Mazda Motor Corporation has developed an injection moulding process that uses a new high-strength plastic to manufacture parts that are stronger, lighter and less expensive to produce. The front end and door module carriers on Mazda's all-new midsize Atenza/Mazda 6, unveiled at the Tokyo Motor Show in October, employ this new long-glass fibre reinforced polypropylene material, resulting in dramatic weight savings, in turn benefiting customers. Lighter weight contributes to improved fuel economy and Mazda plans to gradually expand the use of this material across its entire model lineup. "Using this new high-strength plastic allows Mazda to combine parts and integrate functions, while dramatically lowering vehicle cost and weight," said Kei Kado, Senior Managing Director in charge of Mazda R&D. "This material also is highly recyclable. In the years ahead, Mazda will use this new technology for a generation of new vehicles." Due to the strength requirements, previous module carriers have generally been manufactured from glass-mat reinforced thermoplastics based polypropylene or steel stamped parts. But as these parts are press moulded, it is difficult to combine multiple parts, use deep ribs as an efficient way to increase rigidity and strength, or to achieve thin moulding thicknesses. Also, additional processing was required to remove flashes or burs around openings and at the edges of moulded parts. All of these limitations have made it difficult to achieve substantial reductions in weight and cost. Since steel is not suitable for moulding into complex shapes, there are limits to the extent that multiple parts can be combined, and this has also hindered cost reductions. Injection moulding, in contrast, provides much greater design freedom than press moulding, and it eliminates the need for after-processing to remove flashes. It was not used to produce materials, however, because the glass-fibre used to reinforce the plastic would be damaged in the moulding process, making it impossible to achieve the required level of strength. In order to reduce the damage to the glass-fibre during the moulding process, Mazda uses a polypropylene base material with extremely low viscosity to decrease the amount of pressure applied to the glass-fibre. The strength of the injection moulded parts is further boosted by adding a new type of polypropylene with a high crystalline structure to the mixture to form a composite. Finally, an injection moulding technique was developed, designed specifically for large plastic parts, which subjects the glass-fibre to less pressure than conventional methods. Together, these modifications result in glass-fibre strands that are more than 10 times as long following injection moulding then can be achieved using the old methods. The strength of these injection moulded parts are three times stronger than conventional glass-fibre reinforced polypropylene and exhibit excellent heat resistance. The new technology makes it possible to replace parts from steel stamping. The module carriers produced meet or exceed the strength of press moulded plastic parts. The main features of Mazda's new technology include: · Impact strength is more than three times that of conventional glass-fibre reinforced polypropylene. By using this material for the front end module carrier, Mazda increases the impact strength and is able to use a layout (due to improved moulding flexibility) that further protects the cooling unit and front side frame in collisions. By using this material in the Atenza, rather than a conventional front frame made of steel with improvements designed to achieve the above effects, the weight per vehicle is reduced by about 9 kg. · Due to the effects of the super-low-viscosity component, moulding fluidity is increased by more than 30% over conventional glass-fibre reinforced polypropylene and glass-fibre reinforced nylon. This makes it possible to combine multiple parts, achieve thinner moulding thicknesses, and reduce moulding costs. · Through the use of glass-fibre with longer strands for reinforcement and highly crystalline polypropylene, high-temperature fatigue strength at 120 °C has been boosted to twice that of conventional glass-fibre reinforced polypropylene. High-temperature fatigue strength is even 17% better than glass-fibre reinforced nylon, which is renowned for its heat resistance. Thus the new material provides the high level of durability and reliability demanded of structural body parts. · The super-low-viscosity component results in the formation of a thick plastic layer at the surface of the product. It prevents glass-fibre strands from rising to the surface, resulting in a more attractive exterior finish. Conventional glass-fibre reinforced plastic requires a paint finish, but the new material makes products with no exterior coating possible. · Its base material is polypropylene, which has a high recyclability. It is possible to retain the physical and mechanical properties at the same level as that of conventional glass-fibre reinforced polypropylene, even after recycling. In the years ahead Mazda plans to use this new technology to develop common integrated functionality modules for use in new models, and apply modifications to existing models by employing a new generation of platforms. | 
