Characterization of biodegradable PLLA/PCL and PLLA/PBSL polymeric blends

Recently, much attention has been paid to poly(L-lactic acid) (PLLA), a biodegradable polymer made from starch of potato and cone, as a substitute for petrochemical polymers. PLLA has strength and modulus comparable to commercially available engineering polymers; however, PLLA exhibits brittle fracture behavior especially under impact loading conditions and therefore, toughening of PLLA becomes one of the most important issues in the field of bio-polymer engineering. Just recently, polymer blends of PLLA and ductile biodegradable polymers have been developed in order to improve the ductility of PLLA. In the present study, two different kinds of biodegradable polymer blends were prepared from PLLA, poly(e-caprolactone) (PCL) and poly(butylene succinate-co-L-lactate) (PBSL). The binary blends of PLLA with PCL and PLLA with PBSL were prepared in different proportions. The tensile properties, melting flow index (MFI), and dynamic mechanical analysis (DMA) of these binary blends and virgin polymers were then evaluated. It was found that the addition of PCL and PBSL to PLLA reduced the tensile strength and modulus, whereas the elongation at break and MFI values increased. Morphological analysis of PLLA and PLLA blends on the fractured surface under liquid nitrogen was carried out by scanning electron microscopy (SEM) on both binary blends. The SEM analyses also revealed that all the PLLA/PCL and PLLA/PBSL blends are immiscible blends where the PCL and PBSL phase are finely dispersed in the PLLA-rich phase.