Abstract
Polylactic acid (PLA) is a key biopolymer with potential uses in numerous sectors, since it is biocompatible and both biobased and biodegradable. However, brittleness limits its industrial applications where plastic deformation at high impact rates or high elongation is required, for instance, flexible food packaging. In order to overcome this drawback and potentially expand the PLA market, we developed flexible PLA materials plasticized with renewable and biodegradable epoxidized soybean oil methyl ester reaching elongations at break of almost 800%. The use of amorphous PLA in combination with the lubricating effect of the plasticizer allowed the more sustainable extrusion at a low temperature of 140 °C, preventing the degradation of PLA and at the same time saving energy. Moreover, plasticized films produced, upon handling, significantly less acoustic noise than pure PLA, which is of great importance for food packaging applications. Morphology, thermomechanical and barrier properties, and migration levels were evaluated as a function of plasticizer content.
Highlights
Environmental awareness, concerns regarding sustainability, and depletion of fossil resources, as well as pollution generated by traditional fossil-based plastics have caused a growing interest in the development of new environmentally friendly materials
We present an efficient, solvent-free process for the preparation of flexible polylactic acid (PLA) plasticized with epoxidized soybean oil methyl ester (ESOME) by extrusion melt blending following green chemistry principles[36] and the goals of sustainable development set by the United Nations.[1]
The results show that ESOME undergoes fast biodegradation even when it is blended with PLA, which is known to not biodegrade under these conditions and requires industrial composting settings (Figure S2).[40]
Summary
Environmental awareness, concerns regarding sustainability, and depletion of fossil resources, as well as pollution generated by traditional fossil-based plastics have caused a growing interest in the development of new environmentally friendly materials. The challenges have been summarized by the United Nations as the 17 goals of sustainable development.[1] To address them, biopolymers have been widely studied because they are biodegradable, biocompatible, and/or derived from renewable resources. PLA can be synthesized either by the simple polycondensation of lactic acid or the ring opening polymerization of the cyclic diester of lactic acid lactide.[6,7] obtaining a high molecular weight polymer can be challenging via the former route, an azeotropic dehydration process can be employed to remove water and drive the equilibrium of the reaction toward the product.[8,9] NatureWorks, a world-leading biopolymer supplier, utilizes ring opening melt polymerization of lactide with a tin catalyst, which in general is more commonly employed in industry.[10]
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