This study presents the fabrication and characterization of sustainable polylactic acid (PLA)-based biocomposites reinforced with bio-origin fillers derived from food waste: seashells, eggshells, walnut shells, and spent coffee grounds. All fillers were introduced at 15 wt% into a commercial PLA matrix modified with a compatibilizer to improve interfacial adhesion. Mechanical properties (tensile, flexural, and impact strength), morphological characteristics (via SEM), and hydrolytic aging behavior were evaluated. Among the tested systems, PLA reinforced with seashells (PLA15S) and coffee grounds (PLA15C) demonstrated the most balanced mechanical performance, with PLA15S achieving a tensile strength increase of 72% compared to neat PLA. Notably, PLA15C exhibited the highest stability after 28 days of hydrothermal aging, retaining ~36% of its initial tensile strength, outperforming other systems. In contrast, walnut-shell-filled composites showed the most severe degradation, losing over 98% of their mechanical strength after aging. The results indicate that both the physicochemical nature and morphology of the biofiller play critical roles in determining mechanical reinforcement and degradation resistance. This research underlines the feasibility of valorizing agri-food residues into biodegradable, semi-structural PLA composites for potential use in sustainable packaging or non-load-bearing structural applications.

The COVID-19 pandemic significantly impacted material sciences, particularly polymer composites, which played a crucial role in personal protective equipment (PPE), medical devices, and packaging. This study explores the modifications and advancements in polymer materials developed to meet the urgent demands of the pandemic. Key innovations include enhanced filtration efficiency in PPE, integration of antimicrobial nanoparticles, and the development of biopolymer alternatives to address environmental concerns. The incorporation of silver, copper oxide, zinc oxide, and titanium dioxide nanoparticles improved antiviral and antibacterial properties, while polymer modifications enhanced durability, thermal resistance, and recyclability. Additionally, research into biodegradable polymers such as polylactic acid (PLA) and polyhydroxyalkanoates (PHAs) gained momentum as sustainable alternatives to fossil-based plastics. The findings underscore the necessity of material innovation during global crises and highlight the future potential of modified polymer composites in healthcare and environmental sustainability.