High strength plastic is good for cars
13 Dec 2001
Mazda Motor Corporation has developed an injection moulding process that uses a new high-strength plastic to manufacture 'module carriers' that, it claims, are stronger, lighter and less expensive to produce.
Due to strength requirements, previous module carriers have generally been manufactured from glass-mat reinforced thermoplastics based on polypropylene or steel stamped parts. But as these parts are press moulded, it is difficult to combine multiple parts, use deep ribs as a way to increase rigidity and strength, or to achieve thin moulding thickness.
Also, additional processing has been required to remove flashes or burs around the openings and at the edges of moulded parts. All of these limitations have made it difficult to achieve substantial reductions in weight and cost.
And, since steel is not suitable for moulding into complex shapes, there are limits to the extent that multiple parts can be combined.
Injection moulding, in contrast, provides much greater design freedom than press moulding, and it eliminates the need for after-processing to remove flashes.
Mazda claim that the impact strength of module carriers made using the new process and material is more than three times that of conventional glass-fibre reinforced polypropylene. What is more, the moulding fluidity of the new plastic is 30% greater than conventional glass-fibre reinforced polypropylene and glass-fibre reinforced nylon. This makes it possible to combine multiple parts, achieve thinner moulding thickness and reduce moulding costs.
Better yet, the high-temperature fatigue strength of the material at 120 °C is 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.
The super-low-viscosity material used also results in the formation of a thick plastic layer at the surface of the product that prevents glass-fibre strands from rising to the surface, resulting in a more attractive exterior finish.
Already, 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, and Mazda plans to gradually expand the use of this material across its entire model range.
