Improvement in Mechanical Properties and Heat Resistance of PLLA-b-PEG-b-PLLA by Melt Blending with PDLA-b-PEG-b-PDLA for Potential Use as High-Performance Bioplastics

Supasin Pasee,Yodthong Baimark

doi:10.1155/2019/8690650

Abstract

Ecofriendly poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-b-PEG-b-PLLA) are flexible bioplastics. In this work, the blending of poly(D-lactide)-b-poly(ethylene glycol)-b-poly(D-lactide) (PDLA-b-PEG-b-PDLA) with various blend ratios for stereocomplex formation has been proved to be an effective method for improving the mechanical properties and heat resistance of PLLA-b-PEG-b-PLLA films. The PLLA-b-PEG-b-PLLA/PDLA-b-PEG-b-PLDA blend films were prepared by melt blending followed with compression molding. The stereocomplexation of PLLA and PDLA end-blocks were characterized by differential scanning calorimetry and X-ray diffraction (XRD). The content of stereocomplex crystallites of blend films increased with the PDLA-b-PEG-b-PDLA ratio. From XRD, the blend films exhibited only stereocomplex crystallites. The stress and strain at break of blend films obtained from tensile tests were enhanced by melt blending with the PDLA-b-PEG-b-PDLA. The heat resistance of blend films determined from testing of dimensional stability to heat and dynamic mechanical analysis were improved with the PDLA-b-PEG-b-PDLA ratio. The sterecomplex PLLA-b-PEG-b-PLLA/PDL-b-PEG-b-PDLA films prepared by melt processing could be used as flexible and good heat-resistance packaging bioplastics.

Highlights

In the past few decades, biodegradable bioplastics have been widely developed for use instead of non-biodegradable petroleum-based plastics due to plastic-waste pollution and the implementation of low-carbon environmental protection
The results suggested that stereocomplexation between PLLA-Poly(ethylene glycol) (PEG)-PLLA and PDLA-PEG-PDLA of the blend films improved their tensile properties
The results suggested that the stereocomplexation of PLLA-PEGPLLA/PDLA-PEG-PDLA blends improved the heat resistance of the blend films

Summary

Introduction

In the past few decades, biodegradable bioplastics have been widely developed for use instead of non-biodegradable petroleum-based plastics due to plastic-waste pollution and the implementation of low-carbon environmental protection. PLLA has uses in many fields such as biomedical, food packaging, and agriculture [4,5,6] but its use in some applications is limited by its low flexibility and poor heat-resistance [7, 8]. Stereocomplex polylactides (scPLA) can be formed by blending between PLLA and poly(D-lactide) (PDLA) that had stronger interactions in the stereocomplex crystallites than the homocrystallites of PLLA and PDLA [9]. This induces higher melting-temperatures (approximately 210–240∘C) and faster crystallization speed than the PLLA thereby enhancing the mechanical properties, heatresistance, and hydrolysis-resistance of scPLA [10, 11]. The brittle character of scPLA is still limiting in some applications

Methods

Results

Conclusion