INSULATIVE SHELL STRUCTURE FOAM PROCESS
Original Publication Date: 1983-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
Structural foam can be produced by many subprocesses on different types of equipment. However, it is basically made by injecting a thermoplastic resin in its melted condition with some form of a blowing agent blended into it. This material is injected into a closed mold. The blowing agent produces a foam core in a structure which is sandwiched by a solid skin. The skins have always exhibited a splay-swirl pattern caused by small amounts of blowing agent migrating to the part surface. This pattern must be hidden via the finishing/painting operation to achieve an aesthetically acceptable part. To overcome this problem, a 7 to 20 thousandths of an inch thick plastic sheet material, i.e., cellulose acetate, polycarbonate, etc., thermoformed to the shape of the injection mold cavity is placed in the cavity. The thermoformed plastic sheet is secured adhesively to the cavity.