Opuntia ficus-indica fruit by-products as fillers for PLA-based biocomposites: A comparison between glochids and peel

Abstract

This work explores sustainable and innovative solutions for valorizing by-products from Opuntia ficus-indica (cactus pear), a fruit widely grown in Sicily, the world's second-largest producer. The peel and glochids of cactus pears were used for the first time as fillers in a polylactic acid (PLA) matrix to develop biocomposites. The composites were prepared by incorporating 10% and 20% of peel and glochids separately into PLA using the melt compounding technique. Comprehensive characterization was performed, including morphology, rheology, tensile properties, dynamic-mechanical behavior, calorimetric response, and wettability. The results demonstrated that incorporating 20% glochids led to a 70% increase in storage modulus (E') at 25 °C compared to neat PLA, significantly enhancing stiffness, while peel-reinforced composites exhibited a lower but still notable increase of 39%. Rheological tests revealed distinct behaviors: glochid-reinforced composites exhibited an increase in complex viscosity, whereas peel-reinforced composites showed a reduction. This was linked to a significant reduction, approximately 50%, in the molecular weight of PLA in the presence of peel. This study highlights the potential of cactus pear by-products as sustainable fillers for biocomposites, offering a pathway to reduce agricultural waste while enhancing material performance.