- 1: Materials innovation: supercritical fluids
Mazda mixes supercritical fluid*1 (SCF) made from common inert gases such as nitrogen or carbon dioxide with the resin raw material for plastic parts. The process uses a particular characteristic of SCFs to mix readily with other substances at the molecular level, which raises the fluidity of the liquid plastic resin and causes it to expand rapidly when injected into a mold. As a result, smaller amounts of the raw material resin are needed.
*1 A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Compared to their natural gaseous forms, nitrogen and carbon dioxide, as supercritical fluids, increase the solubility of plastic resin and enable it to form foam with a standardized micro-cell structure.
- 2: Process innovation: Core Back Expansion Molding*2
Core back expansion molding is a new method of injection molding. Once the foamed resin has filled up the mold, the volume of the mold is increased, causing the foam to expand. This means larger plastic parts, with lower density and equal or greater strength and rigidity, can be made from the same volume of plastic resin.
*2 Core Back expansion molding
Mazda has become the first company in the automotive industry to combine these two methods to create a unique technology that reduces the amount of material needed to produce plastic parts. Furthermore, the reduction of raw materials has led to decreased CO2 emissions due to manufacture, use, and end of life processing of plastic parts.
Plastic parts produced with these two innovative processes have a multi-layered structure. The inner layers consist of regularly-sized microscopic bubbles. This structure reduces the density of the parts without affecting strength or rigidity. As well as this added value, the new plastic can be easily recycled.
- Greater rigidity and strength
The diagram to the right shows the rigidity of a door module made with our foamed technology compared with a module made with conventional technology. The foam plastic door module weighs 20% less and is roughly 18% more rigid than the conventional version. In side impact crash tests, the new door module also proved itself to be at least as strong as the current part.
- High added-value and recyclability
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.
Through the use of SCFs, Mazda's foamed resin molding technology does not result in adverse effects from residual chemical compounds, so it has a reduced impact on the environment, and produces parts that can be easily recycled, unlike conventional methods.
Mazda intends to adopt this technology for plastic parts on our next generation platforms that will be introduced from 2011. It will be used to accelerate our weight reduction initiatives.