Poly(l-Lactic Acid)/Pine Wood Bio-Based Composites.

Monika Dobrzyńska-Mizera,Maria Laura Di Lorenzo,Mikołaj Baranowski,Monika Knitter,Tomasz Sterzyński,Aneta Woźniak-Braszak

doi:10.3390/ma13173776

Abstract

Bio-based composites made of poly(l-lactic acid) (PLLA) and pine wood were prepared by melt extrusion. The composites were compatibilized by impregnation of wood with γ-aminopropyltriethoxysilane (APE). Comparison with non-compatibilized formulation revealed that APE is an efficient compatibilizer for PLLA/wood composites. Pine wood particles dispersed within PLLA act as nucleating agents able to start the growth of PLLA crystals, resulting in a faster crystallization rate and increased crystal fraction. Moreover, the composites have a slightly lower thermal stability compared to PLLA, proportional to filler content, due to the lower thermal stability of wood. Molecular dynamics was investigated using the solid-state 1H NMR technique, which revealed restrictions in the mobility of polymer chains upon the addition of wood, as well as enhanced interfacial adhesion between the filler and matrix in the composites compatibilized with APE. The enhanced interfacial adhesion in silane-treated composites was also proved by scanning electron microscopy and resulted in slightly improved deformability and impact resistance of the composites.

Highlights

Application of natural fiber reinforced composites increases in all areas of production, especially the building and automotive industry
The latter appears anticipated compared to plain poly(L-lactic acid) (PLLA) of a few degrees, with the exact temperature being affected by wood content
Composites prepared with PLLA and pine wood, both bio-based, have been produced by twin-screw extrusion in different compositions, from 10 to 30 wt % of filler content, and characterized for their morphology, physicochemical and mechanical properties

Summary

Introduction

Application of natural fiber reinforced composites increases in all areas of production, especially the building and automotive industry They are usually based on commodity polymers, like polypropylene or polyvinyl chloride. Several bio-based and/or biodegradable polymers have been developed commercially, such as polyhydroxyalcanoates, poly(L-lactic acid) (PLLA), polycaprolactone and polybutylene succinate and their derivates [2]. Among those listed, PLLA gained the greatest attention due to its numerous advantages such as being biodegradable and compostable, having good stiffness and strength and being able to be produced on a large scale by microbial fermentation of agricultural byproducts [1,3,4]. Several attempts have been made to outbalance these disadvantages, which mainly include the modification of PLLA formulations to develop material with improved plasticization [6,8], impact resistance [1,9], or crystallization rate [10], often achieved by introduction of particles and fiber-like fillers [11,12,13]

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