Research On The Toughening Modification Of Poly（Lactid Acid） And Foaming Performance Biowing With Supercritical CO₂

Poly(lactic acid) (PLA) was melt-blended with three components-methyl cinyl silicone rubbler(MVQ), fluorine rubber (FPM), and ethylene-methyl acrylate copolymer(EMA)-in an effort to toughen PLA. Microcellular foaming materials were prepared by PLA based composites with supercritical CO2. The property of blends(tensile strength, elongationg at break, and impact strength) and foams(foaming ration, average size of cells, number density of cells, cell morphology) were characterized by performing tensile testing, impact testing, differential scanning calorimertry(DSC), or scanning microscope(SEM) experiments. The effect of component(MVQ, FPM, EMA) on properties of materials have been studied.The results indicated that toughening was achieved when PLA was blended with MVQ, FPM, EMA. The impact strength of PLA/MVQ blends increased by 200%, compared with pure PLA, with 5phr DCP added. The content of FPM bigger, the impact strength value of PLA/FPM blends increased. When FPM of 15 weight percentage added to PLA/FPM blends, we got that value of impact strength and elongation at break increased by 340% and 1400% respectively. And the impact strength value of PLA/EMA blends increased to 73MPa. Meanwhile elongation at break was 205%. Because of the toughness of PLA strengthed, microcellular metierials can be obtained from PLA based blends successfully. Foaming ration of PLA/MVQ foams reached a maximum value in certain external conditions, such as saturation time, foaming temperature, and saturation pressure, and so on. For PLA/FPM foams, average size of cells and number density of cells was 7.5μm and 1.26×109/cm3 respectly at the condition of 140℃ and 15MPa. Under the same contition, the cells size of PLA/EMA foams was in the range of 3 to 8 micrometer and number density of cells is 3×109/cm3～35×109/cm3.