Polylactide (PLA) Composites Reinforced with Natural Fibrous Filler Recovered from the Biomass of Sorghum Leaves or Stems

TL;DR

This study explores using sorghum biomass to create eco-friendly PLA composites, finding that sorghum stems offer better performance than leaves.

Contribution

The novelty lies in evaluating sorghum stems and leaves as natural fillers for biodegradable composites and comparing their mechanical and thermal properties.

Findings

Sorghum stem-based fillers improved stiffness and ductility with better dispersion and adhesion.

Leaf-based fillers increased stiffness but caused brittleness and agglomeration.

All composites showed reduced impact strength and thermal stability compared to pure PLA.

Abstract

In response to environmental pressures and the growing demand for sustainable materials, this study investigates the use of lignocellulosic fillers derived from sorghum (Sorghum bicolor L. Moench) biomass, specifically stems and leaves, as reinforcements in biodegradable polylactic acid (PLA) composites. The aim was to assess the effect of filler type and content (5, 10, and 15 wt.%) on the physicochemical properties of the composites. Sorghum was manually harvested in Greater Poland, separated, dried, milled, and fractionated to particles <0.25 mm. Composites were produced via extrusion and injection molding, followed by characterization using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), tensile and impact testing, density measurements, optical microscopy, and scanning electron microscopy (SEM). Results showed that stem-based fillers provided a better balance between stiffness and ductility, along with improved dispersion and interfacial adhesion. In contrast, leaf-based fillers led to higher stiffness but greater brittleness and agglomeration. All composites exhibited decreased impact strength and thermal stability compared to neat PLA, with the extent of these decreases depending on the filler type and loading. The study highlights the potential of sorghum stems as a viable, renewable reinforcement in biopolymer composites, aligning with circular economy and bioeconomy strategies.

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