An assessment on the effect of trifluoropropyl-POSS and blend composition on morphological, thermal and thermomechanical properties of PLA/TPU

Abstract

The influence of blending ratio and trifluoropropyl polyhedral oligomeric silsesquioxane (POSS) on microstructure, melt and cold crystallization behavior, thermomechanical and thermal stability of melt-blended polylactic acid/thermoplastic polyurethane (PLA/TPU) blends was investigated using various techniques. Morphological observations (TEM and EDX) showed that POSS nanoparticles have a good dispersion state throughout the matrix and localize in both phases and also at the blend interface. POSS nanoparticles hindered the melt crystallization of PLA while enhancing the degree of cold crystallinity of PLA. In addition, the dispersed TPU droplets in PLA matrix induced a nucleation effect on melt crystallization of PLA, especially at low contents. On the contrary, the cold crystallization temperature of PLA shifted to a higher temperature in the presence of TPU phase, but the degree of crystallinity improved in the case of heating with a low rate. Although the addition of TPU to PLA resulted in a decrement in onset degradation temperature, the samples degraded in wider ranges than neat PLA. The onset degradation temperature of samples in inert ambient was declined by the addition of POSS due to its low thermal stability. These nanoparticles slightly enhanced the thermal stability of PLA-rich samples in air ambient but had no sensible effect on TPU-rich samples. The storage modulus values of the PLA/TPU blends gradually decreased with increasing TPU content. In addition, incorporation of POSS nanoparticles, generally, increased the values of storage modulus but reduced the glass transition temperature, proving the lubrication effect of POSS nanoparticles.