Enhanced Interfacial Adhesion of Polylactide/Poly(ε-caprolactone)/Walnut Shell Flour Composites by Reactive Extrusion with Maleinized Linseed Oil.

Sergi Montava-Jordà,Sergio Torres-Giner,Nuria Richart,Luis Quiles-Carrillo,Nestor Montanes

doi:10.3390/polym11050758

Abstract

Novel green composites were prepared by melt compounding a binary blend of polylactide (PLA) and poly(ε-caprolactone) (PCL) at 4/1 (wt/wt) with particles of walnut shell flour (WSF) in the 10–40 wt % range, which were obtained as a waste from the agro-food industry. Maleinized linseed oil (MLO) was added at 5 parts per hundred resin (phr) of composite to counteract the intrinsically low compatibility between the biopolymer blend matrix and the lignocellulosic fillers. Although the incorporation of WSF tended to reduce the mechanical strength and thermal stability of PLA/PCL, the MLO-containing composites filled with up to 20 wt % WSF showed superior ductility and a more balanced thermomechanical response. The morphological analysis revealed that the performance improvement attained was related to a plasticization phenomenon of the biopolymer blend and, more interestingly, to an enhancement of the interfacial adhesion of the green composites achieved by extrusion with the multi-functionalized vegetable oil.

Highlights

Replacement of fossil feedstocks with renewable ones at an equivalent cost is one of the main endeavors of modern plastics industry [1]
The fracture surfaces of the pieces revealed that the maleinized linseed oil (MLO) co-addition favored the particle-to-matrix composites with improved ductility and a minimal loss in mechanical strength and toughness
MLO slighlty improved thermal enhancement of the interfacial adhesion of the PLA/PCL/walnut shell flour (WSF) composites based on the multiple actions stability and reduced rigidity at room temperature

Summary

Introduction

Replacement of fossil feedstocks with renewable ones at an equivalent cost is one of the main endeavors of modern plastics industry [1]. One possible strategy to reduce current cost of bioplastics deals with the incorporation of agro-food residues due to their huge availability and low price. They represent a highly sustainable option for waste valorization. The combination of biopolymers and natural fillers (e.g., lignocellulosic fillers) results in the development of the so-called “green composites” [2]. This term indicates that the composite as a whole, that is, both matrix and reinforcement, originates from renewable resources. Several lignocellulosic fillers derived from food, agricultural, marine, and industrial wastes have been successfully incorporated

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Conclusion