Poly(lactic acid)/Epoxidized Soybean Oil/Organoclay 나노복합체의 열적, 기계적 및 유변학적 특성

Abstract

Poly(lactic acid) (PLA) was melt blended with epoxidized soybean oil (ESO) in an internal mixer and thermal, mechanical and rheological properties of the blends were investigated by means of differential scanning calorimetry, dynamic mechanical analysis, tensile test and small amplitude oscillatory shear rheometry. ESO lowered glass transition temperature, cold crystallization temperature and improved the elongation at break along with a decrease in yield strength and modulus of PLA. Decrease in melt viscosity was observed with the addition of ESO. In the second part of this work, PLA/ESO/organoclay nanocomposites were prepared by melt blending. The X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images showed that ESO facilitated the delamination of silicate layer in the PLA/ESO/organoclay nanocomposites. The thermal properties showed slight increase in glass transition temperature and cold crystallization temperature of PLA. The mechanical analysis showed that the nanoclays improved the stiffness and yield stress of the PLA/ESO blend without large loss of ductility. The rheological studies under dynamic frequency sweep revealed that the nanocomposites exhibited pseudo-solid like behavior at low frequency region. The complex viscosity of the nanocomposites is higher than that of matrix polymer and the nanocomposites showed higher shear thinning behavior as the clay content was increased. Foam processing of the PLA/ESO blends was conducted using supercritical carbon dioxide as a foaming agent, which revealed that the cell formation was facilitated with ESO.