Influence of trifluoropropyl-POSS nanoparticles on the microstructure, rheological, thermal and thermomechanical properties of PLA

Abstract

In this work the influence of polyhedral oligomeric silsesquioxane (POSS) content with trifluoropropyl substituents on the microstructure, rheological behavior, non-isothermal crystallization behavior, thermomechanical and thermal properties of poly(lactic acid) nanocomposites prepared via melt blending was investigated using various techniques for understanding the structure–property relationship. Morphological analysis (SEM, EDX and XRD) showed that POSS particles have a fine dispersion at low content (up to 2.5 wt%) in a polymer matrix but the imposed processing conditions were not able to prevent the formation of large POSS agglomerates at high POSS contents because of strong interaction among the POSS particles. It was observed that only the POSS nanoparticles dispersed almost at molecular level could act as a lubricant in the system since lower values for the glass transition temperature, storage modulus and complex viscosity were observed from DMA and rheological investigations. The viscosity and elasticity of PLA were improved in the presence of high contents of POSS however, the degree of enhancement was not strong enough for a transition from liquid-like to solid-like behavior. In addition, the POSS particles at low loadings had a promoting impact on the cold crystallization of PLA while at high loadings the cold crystallization was retarded. Also, it was found that the presence of POSS slightly reduced the thermal stability of the nanocomposites relative to the neat PLA. However, the thermal degradation mechanism of PLA remained unchanged.