TOKYO - Mitsubishi Motors Corp. has developed an engine cover made from recycled polyethylene terephthalate, or PET, bottles, which it will install on new models to be launched this spring.
Each engine cover uses the equivalent of 22 15-ounce soft drink PET bottles. This represents the first time the recycled material has been used to produce large injection moldings for automotive applications in Japan, although there have been similar applications elsewhere in the world.
Mitsubishi, which developed the recycling process with Toyoda Gosei Co. and Toyobo Co., said the savings from using engine covers made from recycled PET compared with conventional polyamide engine covers came to more than 20 cents per cover.
PET generally offers high viscosity in the molten state and deforms readily when heated, making it ideal for use in stretch-blow molding machines. Those same properties create problems when recycled PET is used for large injection moldings, though, because the molten resin does not flow readily and is difficult to remove from the mold after forming.
The new process, however, uses an additive that increases the material's fluidity and adjusts the temperature used in the molding process to improve formability and heat resistance.
Lightweight and durable, recycled PET is ideal for beverage bottles but has low impact strength. So an engine cover made of the usual recycled PET would crack easily if, say, a tool were dropped on it during engine servicing. Mitsubishi solved that problem by using a strength-enhancing additive and redesigning the engine cover itself to increase impact strength.