Thermal properties and non-isothermal crystallization kinetics of biocomposites based on poly(lactic acid), rice husks and cellulose fibres

Abstract

Bioplastics reinforced by agricultural waste fibres show promise to provide degradation back into the environment when they are no longer needed. These biocomposites have the potential to replace synthetic polymers from non-renewable resources in some applications and may turn out to be one of the material revolutions of this century. Unlike synthetic composites, biocomposites are renewable, carbon neutral, biodegradable and non-petroleum based and have low environmental, human health and safety risks. In this paper, poly(lactic acid) (PLA)-based biocomposites filled with technical cellulose fibres (CeF) and rice husks (RHs) at 10–30 mass% loading were prepared by twin-screw extrusion and injection moulding to enhance stiffness of resulting biocomposites. Particular attention was given to the enhancement of adhesion between the polymer matrix and natural filler through the physical modification by ozone (O3) and dielectric barrier discharge (DBD) plasma (p) surface treatments. Further than, compatibilizing agent based on PLA-g-MAH was produced and introduced into the PLA systems. The non-isothermal crystallization behaviour and thermal properties were investigated through differential scanning calorimetry (DSC) under various cooling rates (5, 10, 20 and 40 °C min−1). The addition of both fillers increased overall crystallization kinetics of resulted biocomposites, especially at high cooling rates. An increase in crystallinity degree from 2.4 (neat PLA) up to 51% has been observed for PLA/30CeFO3 samples at 40 °C min−1 cooling rate. An increase in crystallinity degree based on mass percentage of filler was noticed especially for PLA/RH. Mass percentage increase in CeF did not notice significant increase in PLA crystallinity. The influence of RH and CeF on transformation behaviours of PLA αʹ-/α-polymorphs was observed. The elimination of imperfect αʹ-crystals was observed with increasing amount of RH and CeF.