Gas-assisted compression moulding of recycled GMT: Effect of gas injection parameters

Gas assisted compression moulding (or GasComp) is a novel process based on the injection of nitrogen gas during a conventional compression moulding cycle, a technique originally introduced in the injection moulding industry. The gas is injected into the molten material at a preset gas inlet point, hollowing out the part and thus assisting the compressive force of the press in generating material flow. This paper presents gas injection parameter studies on polypropylene based recycled glass mat-reinforced thermoplastic (GMT). The parameters investigated are gas ramp rate, gas injection delay time, and peak pressure. The size of cavity was found to be inversely proportional to gas injection delay time. Rheological instabilities at the polymer–gas interface were observed; a phenomenon previously noted during the development of gas assisted injection moulding.