การปรับปรุงสมบัติเชิงกลและความร้อนของพอลิ(แอล-แลก ไทด์)โดยการสเตอริโอคอมเพล็กซ์สำหรับใช้เป็นวัสดุบรรจุภัณฑ์

Abstract

Poly(L-lactide) (PLL) is a cost-effective biodegradable polymer derived from renewable resources. Although PLL is commercially available in the market but its applications are still limited due to inherent physical properties. In particular, plastics produced from virgin PLL are brittle and thermally unstable. Stereocomplexation has been a route to solve this drawback by combining PLL with its enantiomer, poly(D-lactide) (PDL). In this work, PLL was blended with triblock copolymers having terminal poly(ethylene glycol) (PEG) as central block and PDL as side block. PDL was initially synthesized through ring-opening polymerization (ROP) of D-lactide, using stannous octoate (Sn(Oct)2) as an initiating system. Triblock copolymers were synthesized by ROP from D-lactide and PEG macroinitiator, using Sn(Oct)2 as a catalyst. Stereocomplex polylactide (Sc-PL) was prepared by melt blending of PLL with PDL and triblock copolymer of different chain lengths at blending weight ratios of 50:50, 60:40, 70:30, 80:20 and 90:10. Sc-PL sheets were fabricated using compression molding and injection molding. Thermal properties, mechanical properties and morphology of Sc-PL were subsequently analyzed. Our results suggest that Sc-PL show its high melting temperature of around 210-220 oC, which is approximately 45-60 oC higher than that of homochiral crystals of PLL or PDL although elongation at break decreased with increasing PDL amount. Heat distortion temperature (HDT) is increase after annealing. Moreover, blending PLL with triblock copolymers results in high melting temperature of around 210-215 oC, which is approximately 45-50 oC higher than that of homochiral crystals of PLL or PDL, and leads to increase in elongation at break of around 3 % using 10 wt% triblock copolymers. Similar to virgin PLL, the developed Sc-PL containing 10 wt% triblock copolymers allows fabrication of tray by means of thermoforming. The Sc-PL developed in this study is hence an alternative to conventional polymers as being an eco-friendly heat resistant packaging material.