EFFECTS OF TALC AND COMPOUNDING ON MORPHOLOGY AND MECHANICAL PROPERTIES OF LOW-PRESSURE-INJECTION-MOLDED STRUCTURAL POLYLACTIDE FOAMS

摘要

Low-pressure structural molding of linear polylactide (PLA) foams with high void fraction (～ 30%) and relatively uniform structure was conducted and characterized. Three different material systems namely as received PLA, processed PLA and PLA/talc compound were investigated in order to assess the sole effect of processing and addition of talc on the foaming behavior, structure uniformity and mechanical properties of PLA foams. The cell density, cell size, local void fraction, and the corresponding cavity pressures during the injection cycle were measured at three different sample locations— i.e., near the gate, at the middle, and at the end of the components. The mechanical properties of the samples were also measured using ASTM standard tensile test. Overall, the addition of 5 wt% talc improved the foaming ability achieving greater cell density and smaller cell size, and increased the structure uniformity throughout the sample. Furthermore, the addition of talc significantly improved the tensile properties of PLA foams such as specific modulus, strength, toughness and strain at break. Compounding process appeared not to affect the foaming behavior of neat PLA while deteriorated the mechanical properties of foams.