Thermoplastic Foam Casting (TFC) also called Structural Foam Molding (SFM)is a low-pressure injection molding process that is capable of producing very large structural parts. The molten plastic material is injected into a mold after being mixed with a blowing agent or high-pressure gas. This produces bubbles in the plastic causing it to foam. The foam retains the properties of the plastic but weighs less because of reduced density.
Structural foam molding is similar to the injection molding process, structural foam molding is a low pressure method of processing thermoplastics, with the most commonly used resin being HDPE (high density polyethylene). The end product is typically a rigid part with a relatively hard surface. Structural foam should not be confused with expanded polystyrene (EPS), which can be associated with the white disposable foam blocks that package and protect new appliances and electronics.
The key element in structural foam molding is low pressure. Unlike conventional injection molding, which utilizes extremely high pressures to force materials into a mold's cavity, structural foam molding takes advantage of a part's configuration, its generally thick wall sections (that act as runners), and the foaming action (supplied by either chemical reaction within the resin blend, or the introduction of a compressed, inert gas into the mold), to allow the molten resin to flow much further, and with far lower pressure, than the typical injection molding process would allow.