Comparison of thermal, mechanical and thermomechanical properties of poly(lactic acid) injection-molded into epoxy-based Rapid Prototyped (PolyJet) and conventional steel mold

摘要

The number of renewable-resource-based and inherently biodegradable poly(lactic acid) (PLA) products is growing in the market, resulting in an increasing demand to produce even small series of injection-molded PLA prototypes for testing purposes by using rapid molds. In our research, it was first demonstrated that it is possible to use epoxy-based molds made by PolyJet Rapid Prototyping technology for conventional injection molding to produce small series of PLA parts. The effect of mold material, namely conventional steel mold and epoxy-based PolyJet mold, was analyzed on the thermal and mechanical properties of the injection-molded products. PLA was used with no, moderate and high nucleating agent contents [talc and poly(ethylene glycol)] to obtain a model material with slow, moderate and high crystallization rates, respectively. It was demonstrated that the mold used and thus the thermal conductivity of the mold had significant effect on the crystallinity of the PLA parts and thus on its mechanical and thermomechanical properties. Finally, it was found that it is possible to mimic the thermomechanical properties of nucleated PLA injected into hot mold used for mass production by injecting it into the epoxy-based PolyJet mold used for small series production.