Functional poly (vinyl alcohol)/sapindus mukorossi shell particulate biocomposites: Toward sustainable thermoplastic materials for packaging applications

This study investigates the development of environmentally friendly thermoplastic biocomposite films based on a polyvinyl alcohol matrix, utilising underutilised Sapindus mukorossi shell particulates as bio-based fillers. SMSP was added at various loadings, and the resulting composites were thoroughly characterized. Spectroscopic analysis confirmed the presence of strong intermolecular hydrogen bonding between PVA and SMSP, even without chemical modification, while X-ray diffraction revealed enhanced molecular ordering. Thermal stability improved with an increased char yield from 0.83% for pure PVA to 17.6% with 25 wt% SMSP. Mechanical properties peaked at a tensile strength of 48.4 MPa, Young’s modulus of 69.9 MPa, and puncture strength of 54.5 MPa with 20 wt% SMSP, while higher filler contents caused minor agglomeration and reduced efficiency. It was observed that the barrier properties increased, reflected by a reduction in water uptake and water vapour permeability with increasing diffusion tortuosity. The water absorption and solubility were reduced to 31.1% and 34.6%, respectively, while the water vapour permeability demonstrated almost a 48% reduction in the case of the highest loaded SMSP content. AFM images showed increased surface roughness, enhancing mechanical interlocking. The optical transparency reduced with an increase in filler content as a result of light scattering, showing effective UV-shielding characteristics. This work hence establishes that the mechanical, thermal, and barrier properties of PVA films are improved upon reinforcement with Sapindus mukorossi shell particulates, illustrating the potential of this underused bio-waste as a low-cost, biodegradable, and high-performance reinforcement for sustainable thermoplastic packaging applications.