Effect of poly(ɛ-caprolactone-co-L-lactide) on thermal and functional properties of poly(L-lactide)

A blend of poly(L-lactide) (PLLA) with star-shaped poly(ɛ-caprolactone-co-L-lactide) (s-PCLA) at different contents (PLLA/s-PCLA=100/0, 90/10, 80/20, and 70/30, w/w) were prepared by torque rheometer. Thermal and functional properties of the blends were investigated by FTIR, SEM, DSC, TGA, DMA, tensile, optical, and water vapor permeability tests. FTIR results showed that intermolecular hydrogen bonds existed between two components in the blends. SEM indicated that PLLA and s-PCLA showed limited miscibility. DSC showed that Tg occurred at lower temperatures in the PLLA/s-PCLA blends than in neat PLLA, and the crystallinity of PLLA phase increased by the presence of s-PCLA in the PLLA/s-PCLA blends. TGA indicated that s-PCLA improved the thermal stability of the PLLA/s-PCLA blends. DMA results revealed that the storage modulus of the composites decreased with respect to the pure polymer. The result of tensile tests suggested that the PLLA/s-PCLA blends showed better elongation at break than neat PLLA. The effect of s-PCLA on the color and opacity of films could be considered as negligible. The WVP of PLLA/s-PCLA blend films increased with the increase in s-PCLA, and they were still lower than that of commercial LDPE films.