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1 March 2000, Tokyo: Mitsubishi Motors announces that, working with Toyoda Gosei Co. Ltd. of Aichi Prefecture and Toyobo Co., Ltd. of Osaka, it has developed an eco-friendly engine cover made from recycled PET(*1) resin polymer bottles.
The new engine cover uses material from PET bottles that have been: (1) Thrown out as incombustible garbage by ordinary consumers, (2) Collected by local governments and, (3) Processed by recyclers, as laid down in the Law for Recycling of Containers and Packaging enacted on 1 April 1997. Each engine cover uses the equivalent of 22 500ml soft-drink PET bottles and represents the first time the material has been used to produce large injection moldings for automotive use in Japan, and joins a very small band of similar applications elsewhere in the world.
To date, RPET(*2) has been reused mostly in the production of textiles products and bottles for medicines and chemicals and Mitsubishi Motors has also recently started to use the material in carpets, floor mats and other textiles. The use of the material in the manufacture of engine covers and other large plastic products has presented significant difficulties due to problems relating to molding methods and to the wide variety of material properties required in different products.
In Japan, 282,000 tons of PET bottles were produced in 1998 for use as containers for soft drinks, soy sauce and alcoholic beverages, with a 16.9% recovery rate. The forecast for 1999 is 327,000 tons and 18% respectively. In future, a major increase in the recovery rate is expected as a result of: heightened awareness regarding recycling on the part of the consumer; an increase in the number of local governments which collect pre-sorted garbage; and the fact that in April this year the range of PET bottles subject to the Container and Packaging Recycling Law is to be extended and the number of designated recyclers to set to increase. The use of RPET in the manufacture of engine covers by Mitsubishi Motors is a positive contribution to the search for new uses for the material.
Mitsubishi Motors will start using engine covers made using RPET in models
to be launched from this spring. The company will continue its research
and development activities in order to find applications for, and to
put to practical use, a variety of recycled materials.
(*1) PolyEthylene Terephthalate
(*2) Recycled PET
Engine cover made using recycled PET bottles
1. Development of new engine cover
(1) Improved RPET formability, heat resistance
Features of the material used in PET bottles include its high viscosity in the molten state and the way it readily deforms when heated; these properties being required because it is manufactured for use in stretch-blow molding machines. However, these properties create problems when RPET is used for large injection moldings because the molten resin does not flow readily and because it is difficult to remove from the mold after forming. These problems cause major difficulties, particularly in the manufacture of large moldings such as an engine cover with a projected area of 1,900 cm2.
Mitsubishi Motors has developed a solution to these problems by adjusting the molecular weight of RPET, by using an additive that increases its fluidity, and by adjusting the temperature used in the molding process, thereby improving its formability and heat resistance.
(2) Performance exceeds polyamide resin
Light in weight and durable, RPET is an ideal material for use in beverage bottles. However, it has a low impact strength in its original form and an RPET engine cover would crack easily were a tool to be accidentally dropped on it during engine servicing, or when being dismantled.
Mitsubishi Motors has solved this problem using a strength-enhancing additive and by modifying the design and shape of the engine cover itself to realize an impact strength equal to or greater than an equivalent cover made from polyamide resin.
| Fluidity comparison
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Impact strength comparison
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2. Features of new RPET engine cover
(1) Cost-performance
The use of improved RPET realizes a cost reduction of several tens of yen over conventional polyamide engine covers.
(2) Eco-friendly
Each new engine cover uses the equivalent of 22 500-ml soft-drink PET bottles and uses RPET only - no virgin PET is used. As well as making for the more effective use of petroleum resources, by providing another application for RPET the new engine cover also contributes to solving the problem of finding uses for recycled PET bottles.
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