Valorisation of Hazelnut Shell Powder (HSP) in the production of biobased and recyclable composites

Biocomposites based on natural fibers waste and biopolymers are currently explored because of their renewability, biodegradability and the accordance with the circular economy principles. Among the sources derived from agro-food waste, hazelnut shells can be of considerable interest because of their wide availability. This waste is composed of 90% of a lignocellulosic fraction with crude fiber accounting for over 85%. Considering the high amount of lignin and a predominantly fibrous structure, the hazelnut shell is considered a highly stiff material. Thus, it can be considered suitable as mechanical reinforcement for the production of biocomposites. Additionally, the recyclability of these biocomposites can be enhanced thanks to the possible addition of biobased processing aids, as they can enable a fine tuning of melt viscosity. In the present work, biocomposites having a poly(lactic acid) (PLA) based matrix were produced by extrusion, considering different HSPs concentrations with the aim to obtain final biocomposites with a high filler quantity, acceptable mechanical properties and good melt fluidity. Moreover, methodologies to contrast the reduction of molecular weight through the use of biobased chain extenders were also investigated. Biobased chain extenders, consisting of epoxidized soy bean oil (ESO) and dicarboxylic acids from agro-food waste were used in a PLA/poly(butylene succinate-co-adipate) (PLA/PBSA) binary blend matrix reinforced with HSP.