Fully Biobased Reactive Extrusion of Biocomposites Based on PLA Blends and Hazelnut Shell Powders (HSP)

Luca Panariello,Alessandro Vannozzi,Andrea Lazzeri,Maria-Beatrice Coltelli,Laura Aliotta,Daniele Bonacchi

doi:10.3390/chemistry3040104

Luca Panariello, Alessandro Vannozzi + Show 4 more

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https://doi.org/10.3390/chemistry3040104

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Abstract

The production of biocomposites based on natural fiber waste and biopolymers is constantly increasing because of their renewability, biodegradability, and the accordance with the circular economy principles. The aim of this work is to contrast the disadvantages in the production of biocomposites, such as reduction of molecular weight through the use of biobased chain extenders. For this purpose, epoxidized soybean oil (ESO) and dicarboxylic acids (DCAs) were used to contrast the slight chain scission observed in a poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) binary blend caused by the melt mixing with hazelnut shell powder (HSP). Two different dimensions of HSPs were considered in this study as well as different concentrations of the ESO/DCA system, comparing succinic acid and malic acid as dicarboxylic acids. Melt viscosity parameters, such as torque and melt volume rate (MVR), were measured to investigate the chain extender effect during the extrusion. In addition, the reactivity of the ESO/DCA system was investigated through infrared spectroscopy. The effect of chain extenders on thermal properties, in particular on the crystallinity of PLA, and on mechanical properties of final biocomposites was investigated to understand their potentialities in industrial application. Results of this study evidenced a modest increase in melt viscosity due to ESO/malic acid chain extension system, but only for the HSP with the lower dimension (so the higher surface area) and adding 0.5 wt.% of ESO/malic acid. Thus, the slight chain scission of polyesters, not significantly affecting the final properties of these biocomposites, is the most relevant effect that was revealed in this complex reactive system.

Highlights

Bioplastics are considered an environmentally-friendly alternative to replace fossilbased plastics [1]
Were added in biocomposites (ESO) and malic acid (MA) or succinic acid (SA) were added in biocompositescomposed composed by a poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) blend matrix reinforced with hazelnut shell powders (HSPs) having two different dimensions
Integrating the data of torque recorded during extrusion and melt volume rate measured on the prepared biocomposites, it was possible to investigate the system as a function of the adopted dicarboxylic acid (DCA), the epoxidized soybean oil (ESO)/dicarboxylic acids (DCAs) content, and the dimension of HSP

Summary

Introduction

Bioplastics are considered an environmentally-friendly alternative to replace fossilbased plastics [1]. The use of bioplastics is interesting in fields such as packaging because of their recyclability and compostability that guarantee a versatile and sustainable end-of-life [2]. Their use in a wide range of applications in the biomedical field for the preparation of scaffolds [3], wound dressing [4,5], and artificial membranes [6]. A significant group of biobased materials is represented by composites where natural fillers such as flax, wood, hemp or cellulose fibres, cellulose nanowhiskers, bran, nuts or wood flour are embedded in a biodegradable plastic matrix, since this strategy leads to fully biodegradable materials [10,11,12]. The hydrophilicity of natural fillers can accelerate the degradation kinetic of bio-

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