The use of alkali treated walnut shells as filler in plasticized poly(lactic acid) matrix composites

Different amounts of walnut shell flour have been added to poly(lactic acid) polymer plasticized with 10 wt% epoxidized linseed oil to prepare biocomposites. The novelty of this work is the preparation and characterization of biocomposites based on alkali treated walnut shell flour and plasticized PLA matrix. Alkali treatment removed the major part of non-cellulosic components of walnut shell improving the thermal stability and crystallinity index. Furthermore, alkali treatment unproved the adhesion between walnut shell and plasticized PLA matrix and consequently, the tensile strength value of composite improved around 50 %, compared with untreated counterpart. Nevertheless, the tensile strength and Young's modulus values of biocomposites with treated walnut shell were similar to unfilled blend and maintained almost constant irrespective to the filler content. Despite the elongation at break decreased after the addition of walnut shell, the prepared biocomposites showed similar ductility to non-plasticized PLA polymer.