Structural foam is a low-pressure form of injection molding, which utilizes most thermoplastics, (including post-consumer regrind), to mold rigid products, which can have thicker walls and higher stiffness-to-weight ratios than standard injection molded products.

In the structural foam molding process, a physical or chemical blowing agent is mixed in with the resin. The resin is shot into the cavity, but not completely filled or packed out. The blowing agent expands to push the resin to the extremities of the cavities. As the part cools, the internal pressure of the foaming action takes up the internal shrinkage, and reduces sinks over ribs or heavy cross-sections.

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Structural foam molding minimizes molded-in stress that can lead to warpage and part deformation. Other advantages include less energy usage due to the low-pressure process and cost savings and sustainability from using less resin and less-expensive aluminum tooling. Also, versatility in part geometry, from thin walls to very thick and large shapes, is an additional benefit of using structural foam. Aesthetically, the foaming bubbles in the matrix pack out the resin and reduce the incidence of sink on the exterior show side of the plastic part.

There are many advantages of the structural foam injection molding which combine to provide an economical advantage over other processes, and allow production of parts which can’t be matched by any other process. Following is a list of many of the advantages of the structural foam molding process: