Poly(lactic acid)/thermoplastic starch sheets: effect of adipate esters on the morphological, mechanical and barrier properties

Marianne Ayumi Shirai,Juliana Bonametti Olivato,Maria Victória Eiras Grossmann,Ivo Mottin Demiate,Carmen Maria Olivera Müller,Fabio Yamashita

doi:10.1590/0104-1428.2123

Abstract

Blends of poly(lactic acid) (PLA) and thermoplastic starch (TPS) plasticized with adipate esters (diisodecyl adipate and diethyl adipate) having different molecular weight were used to produce sheets. The calendering-extrusion process at a pilot scale was used, and the mechanical, barrier, and morphological characterization of the obtained materials were performed. The increase in the TPS content affected the mechanical properties of the sheets by increasing the elongation and decreasing the rigidity. TPS conferred a more hydrophilic character to the sheets, as observed from the water vapor permeability results. The sheets plasticized with diisodecyl adipate (DIA), having a higher molecular weight, had better mechanical and barrier properties than diethyl adipate (DEA) plasticized sheets, indicating that DIA was more effective as plasticizer. Micrographs obtained by confocal laser microscopy and scanning electron microscopy showed different morphologies when different proportions of PLA and TPS were used (dispersed or co-continuous structures), which were strongly associated with the mechanical and barrier properties.

Highlights

The interest in producing plastic materials from natural The addition of thermoplastic starch (TPS) into a poly(lactic acid) (PLA) matrix can decrease resources is considerably increasing as the need for the the material cost and increase its biodegradation rate[5,7,8].reduction of the amount of plastic waste in the environmentBlending native starch with PLA could increase its rigidity becomes urgent[1]
The current study focuses on the production of sheets with different proportions of TPS and PLA and plasticized with two different adipate esters
It was not possible to produce sheets with PLA/TPS proportions of 20/80 and 10/90, because the extruded materials were too stiff to be processed through the calender rolls

Summary

Introduction

Blending native starch with PLA could increase its rigidity becomes urgent[1]. Low cost, and but simultaneously greatly reduce its elongation at break worldwide availability, starch in the form of thermoplastic and impact strength[9]. PLA has an inherent brittleness as evidenced by obtained by destroying the crystalline structure of native its relatively low tensile strain at break, and toughness[10,11]. Starch through an extrusion process in the presence of Another explanation is linked to the inherent incompatibility plasticizers, such as glycerol[2,3,4]. TPS-based materials are hygroscopic and have limited performance. To overcome this deficiency, It is well known that the mechanical and barrier properties of polymer blends are strongly related to their morphology

Methods

Results

Conclusion