Foam injection molding of poly(lactic acid) with physical blowing agents

Foam injection molding uses environmental friendly blowing agents under\udhigh pressure and temperature to produce parts having a cellular core\udand a compact solid skin (the so-called ``structural foam''). The\udaddition of a supercritical gas reduces the part weight and at the same\udtime improves some physical properties of the material through the\udpromotion of a faster crystallization; it also leads to the reduction of\udboth the viscosity and the glass transition temperature of the polymer\udmelt, which therefore can be injection molded adopting lower\udtemperatures and pressures. These aspects are of extreme interest for\udbiodegradable polymers, which often present a very narrow processing\udwindow, with the suitable processing temperatures close to the\uddegradation conditions.\udIn this work, foam injection molding was carried out by an instrumented\udmolding machine, able to measure the pressure evolution in different\udpositions along the flow-path. The material adopted was a biodegradable\udpolymer, namely the Poly(lactic acid), PLA. The effect of a physical\udblowing agent (PBA) on the viscosity was measured. The density reduction\udand the morphology of parts obtained by different molding conditions was\udassessed.[