Japanese auto maker, Mazda Motor Corporation has developed a new plastic molding technology that enables a substantial reduction in the weight of plastic parts used in vehicles. The new molding technique lessens the use of plastic resins as raw materials by 20-30%. Mazda's improved injection molding process involves mixing supercritical fluid (SCF) made from common inert gases such as nitrogen or carbon dioxide, with the plastic resin raw material. The process utilizes a particular characteristic of SCF to mix readily with other substances at the molecular level to raise the fluidity of the liquid plastic resin and cause it to expand rapidly when injected into a mold. As a result, smaller amounts of the raw material resin are needed to fill molds. The use of SCFs instead of gas formed through thermal decomposition, Mazda's foamed resin molding technology does not result in adverse effects from residual chemical compounds, has a smaller impact on the environment, and produces parts that can be easily recycled.
Furthermore, by using a "core back expansion molding process" - which enables thicker parts to be manufactured using less plastic raw material - Mazda has successfully developed plastic with a multi-layer structure. The bubbles in the outer layer of the plastic are kept microscopic to ensure each part has the necessary strength and rigidity, while the size of the bubbles in the core layer can be freely adjusted to reduce its density as desired.
With this proprietary technology, substantially less material is needed to manufacture plastic parts that are lighter though retaining the strength and rigidity. This plastic foam molding technology can potentially be applied to nearly all plastic parts used in vehicles. Because the core back molding process enables control of the foam's structure, it is possible to add extra value by enhancing the heat insulation and acoustic characteristics of plastic parts.