The Modification Of Polylactic Acid By Poly(propylene Carbonate)

The influence by stearic acid calcium(CaSt2)on the properties of uncapped poly(propylene carbonate)(PPC-1)was studied in this paper.The PPC-1/CaSt2 blends were prepared with torque rheometer.The properties of blends were investigated with Ubbelohde viscosity meter,differential scanning calorimetry,scanning electron microscope,UV-Vis-NIR spectrophoto meter and so on.The results show that the melt viscosity and thermal stability was greatly improved by the introduction of CaSt2,and the mechanism was explored in that chapter.Poly(lactic acid)(PLA)and aliphatic polycarbonate capped with maleic anhydride(PPC-2)blends were prepared via melt blending method and solution casting method respectively,(another blend,PLA/PPC-3 was also prepared via melt blending method,as PPC-2,PPC-3 was capped with maleic anhydride and produced from another manufacture,the properties of blends was discussed in the last chapter),The properties of PLA/PPC-2 blends were investigated with torque rheometer,differential scanning calorimetry,scanning electron microscope,UV-Vis-NIR spectrophoto meter and so on.Our studies focuse on the influence of different preparation methods on the properties of PLA/PPC-2 blends.The results show that PLA and PPC were partially miscible.Physical aging of the blends happen during storage at room temperature.The water vapor barrier property is improved by the introduction of PPC,but dramatically decreased under elevated temperature,especially for blends with high PPC content.The addition of PPC leads to an increase in elongation at break,but a decrease in tensile strength and Young modulus.Melt blending results in thermal degradation of PLA/PPC blends,so the viscosities of melt-blending samples decrease.Compared with solution-casting samples,melt-blending samples show lower elongation at break and better water vapor barrier property.