Characterization of the mechanical and thermal properties and morphological behavior of biodegradable poly(L‐lactide)/poly(ε‐caprolactone) and poly(L‐lactide)/poly(butylene succinate‐co‐L‐lactate) polymeric blends

Abstract

Two series of biodegradable polymer blends were prepared from combinations of poly(L-lactide) (PLLA) with poly(e-caprolactone) (PCL) and poly(butylene succinate-co-L-lactate) (PBSL) in proportions of 100/0, 90/10, 80/ 20, and 70/30 (based on the weight percentage). Their mechanical properties were investigated and related to their morphologies. The thermal properties, Fourier transform infrared spectroscopy, and melt flow index analysis of the binary blends and virgin polymers were then evaluated. The addition of PCL and PBSL to PLLA reduced the tensile strength and Young's modulus, whereas the elongation at break and melt flow index increased. The stress-strain curve showed that the blending of PLLA with ductile PCL and PBSL improved the toughness and increased the thermal stability of the blended polymers. A morphological analysis of the PLLA and the PLLA blends revealed that all the PLLA/ PCL and PLLA/PBSL blends were immiscible with the PCL and PBSL phases finely dispersed in the PLLA-rich phase.

Fracture Mechanisms of Biodegradable PLA and PLA/PCL Blends

“…Blending with ductile biodegradable polymers such as PCL (Broz, 2003;Dell'Erba, 2001;Chen, 2003;Todo, 2007;Tsuji, 1996Tsuji, , 1998Tsuji, , 2001Tsuji, , 2003, poly(butylene succinate-co-ε-caprolactone) (PBSC) (Vannaladsaysy, 2010) and poly (butylene succinate-co-L-lactate) (PBSL) (Shibata, 2006(Shibata, , 2007Vannaladsaysy, 2009;Vilay, 2009) has extensively been investigated in order to improve the fracture energy of PLA. Amoung of them, PCL is known to be bioabsorbable and bioaabsorbable, therefore has been applied in medical fields.…”

Poly(Lactic Acid) Blends

“…They reported that PBSL was more effective in promoting the crystallization of PLLA and increasing the elongation at break than PBS. Furthermore, PBSL/PLLA blends exhibited slightly higher mechanical and thermal properties than PCL/PLLA blends [151,166]. The use of 2 wt% LTI promoted compatibility of the PBSL/ PLLA blend (20/80), as shown in Figure 16.12, by an unclear interface between the two phases, as well as an improvement in the fracture property [167].…”

“…As expected, increasing the amount of ductile PBSL reduced strength and stiffness (strength and tensile and flexural modulus) and promoted flexibility (elongation at break) and toughness of PBSL/PLLA blends compared to PLLA [151,165,166]. The thermal stability and MFI (melt flow index) of these blends gradually increased with PBSL content; with 30 wt% PBSL, the blend had thermal stability higher than that of neat PLLA over the whole tested temperature range [166]. An increase of PBSL content also enhanced cold crystallization and both isothermal and nonisothermal crystallization of PLLA [151].…”

“…Melt blends of PBSL/PLA are immiscible and a morphology of PBSL domains dispersed in a PLA matrix was observed with a high amount of PLLA (!60%) [151,[165][166][167]. As expected, increasing the amount of ductile PBSL reduced strength and stiffness (strength and tensile and flexural modulus) and promoted flexibility (elongation at break) and toughness of PBSL/PLLA blends compared to PLLA [151,165,166]. The thermal stability and MFI (melt flow index) of these blends gradually increased with PBSL content; with 30 wt% PBSL, the blend had thermal stability higher than that of neat PLLA over the whole tested temperature range [166].…”

“…In addition, PBSL behaved as an effective nucleator below 120 C [165]. Shibata et al [151] and Vilay et al [166] compared the properties and characteristics of PBSL/PLLA blends with PBS/PLLA or PCL/PLLA blends. They reported that PBSL was more effective in promoting the crystallization of PLLA and increasing the elongation at break than PBS.…”