Fabrication and Characterization of Poly(lactic acid) Biocomposites Reinforced by Calcium Sulfate Whisker

The biodegradable poly(lactic acid) (PLA) composites filled with calcium sulfate whisker (CSW) were fabricated via melt-blending and subsequent injection molding. Surface organification of γ-aminopropyltriethoxysilane (APTES) on CSW was applied to accelerate the wettability of PLA to CSW. The mechanical properties, morphological structures, crystallization behaviors and thermal stabilities of PLA/CSW composites were investigated in detail. Results showed that modification of APTES changed the surface morphologies and element compositions, helping to form the well bonded interfaces. By adding CSW, the elastic modulus of PLA/CSW composites presented a sustained increment, while tensile strength, elongation at break and impact toughness were increased first and then decreased. The presence of CSW impeded the melt-crystallization but accelerated the cold-crystallization process. On the whole, the actual crystallinity for the composites was suppressed except for the case with 20% CSW. The thermal stability was enhanced by CSW as expected, and all the samples showed the exact same reaction order (n = 1) according to Carrasco method. Nevertheless, the activation energies were declined, indicating CSW was in favor of thermal decomposition of PLA phases. Finally, it was interestingly found that CSW could improve the comprehensive properties of PLA without deteriorating the processibility.