Pea Pod Valorization: A Green Processing Route to Obtain Cellulosic Reinforcements for Compression Molded Polylactic Acid Biocomposites

TL;DR

This paper explores using treated pea pods to create cellulosic reinforcements for biocomposites, improving their mechanical and thermal properties in a sustainable way.

Contribution

A novel green processing route using low-concentration organic acid treatments to enhance pea pod-derived cellulosic reinforcements for biocomposites.

Findings

Cellulosic reinforcements treated with 0.75 M and 0.5 M oxalic acid showed the highest crystallinity (91–92%).

Composites with 20 wt.% of 0.5 M OA and KOH-treated pea pods showed 35/25% higher flexural modulus/strength than pure PLA.

Treated agroresidues can effectively tune mechanical, thermal, and water absorption properties of biodegradable composites.

Abstract

The valorization of agroindustrial residues represents a sustainable alternative in the production of materials attractive for sustainable technologies. In this work, cellulosic materials were isolated from treated pea pods aiming to obtain highly crystalline, thermally stable reinforcements for biocomposites. Four different treatments were evaluated; two employed 0.5 or 0.75 M oxalic acid (OA) solutions at 90 °C, and two used 5% w/v KOH solutions after each OA treatment. The cellulosic materials (10, 20 wt.%) were compounded with a polylactic acid (PLA) matrix and polyvinyl alcohol (0, 2.5 wt.%) as a compatibilizer by extrusion. Compression molding was used to obtain samples to study the composite’s mechanical and thermal behavior. The cellulosic materials and the composites were characterized by Fourier transform infrared spectroscopy, thermogravimetry, and calorimetry. The composites were also subjected to flexural, thermo-mechanical, and water absorption testing. The cellulosic reinforcements obtained using 0.75 M OA and 0.5 M OA and KOH showed the highest crystallinities (91–92%). In general, 20 wt.% reinforced composites showed lower thermal expansion and higher water absorption than those incorporating 10 wt.% reinforcements. The composites incorporating 10 wt.% of 0.5 M OA treated pea pods exhibited flexural modulus/strength 17/3% higher than that of PLA. The composites incorporating 20 wt.% of 0.5 M OA and KOH-treated pea pods showed the highest flexural modulus/strength, 35/25% higher than that of PLA. These results show that agroresidues treated with low-concentration organic acids can be effectively used to tune the mechanical, thermal, and water absorption behavior of biodegradable composites.

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