Gas Counter Pressure and Co-Injection Molding with Chemical Foaming Agents

Gas counter-pressure molding is an injection molding process where the mold is pressurized with an inert gas. This pressure pushes the injected foam melt against the mold walls forming a hard, solid skin. The inert gas is then released from the mold allowing the foam to expand within the part.

Co-Injection injection molding, also known as sandwich molding, allows for the injection of two dissimilar plastics. One injection unit shoots a solid plastic, the other a plastic containing a chemical foaming agent. The solid plastic injection stage begins a split second before the foamed plastic stage causing the foamed plastic to move to the inside of the solid material. The end product displays a solid skin with a foamed core.

Foamazol™ chemical foaming agents yield a good density reduction while maintaining a good surface appearance. Bergen International also offers products for both Gas Counter Pressure and Co-Injection Molding, when surface appearance is critical in molded part applications, but significant part weight reductions is also required.

These two processes allow for the gasses released by Foamazol™ to form cellular structures in the core of the part which is encapsulated by smooth skins. Products such as Foamazol™ 22, Foamazol™ 95, and Foamazol™ 1002 are great choices when looking to foam ABS, Polycarbonate, and PPO respectively in gas counter pressure molding.