The Effect of Fibre Loading on the Thermal, Physical, and Mechanical Properties of Waste Tire Rubber-Reinforced Polylactic Acid (PLA) Composites

Abstract

This study investigates the effects of incorporating waste tyre rubber (WTR) fibres on the mechanical, morphological, thermal, and physical properties of polylactic acid (PLA) composites. WTR fibres, sourced from end-of-life tyres, were introduced into the PLA matrix at weight fractions of 2.5%, 5%, and 7.5% using a single-screw extrusion method to produce composite filaments. Mechanical testing, conducted in accordance with ASTM D638, showed a consistent improvement in tensile performance as WTR content increased. The 7.5% WTR composite achieved the highest tensile stress and Young’s modulus, measured at 26.43 MPa and 1822.41 MPa, respectively. Morphological analysis via Scanning Electron Microscopy (SEM) revealed that higher fibre loading enhanced fibrematrix adhesion, reduced voids, and increased fibre breakage, all of which are indicative of effective stress transfer under load. In contrast, the 2.5% composite exhibited noticeable voids and signs of poor interfacial bonding. Thermal and physical evaluations using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and surface texture analysis indicated that the inclusion of rubber fibres improved thermal stability and water resistance, likely due to the fibres’ inherent heat resistance. Slight increases in surface roughness were also observed, which may influence the composite’s surface characteristics and adhesion properties. Notably, these enhancements in mechanical and thermal performance were achieved without compromising the ductility of the PLA matrix. Overall, the 7.5% WTR composite demonstrated the most balanced and enhanced properties, highlighting its potential as a sustainable and cost-effective material for structural applications, while also contributing to environmentally responsible waste tyre management.