Characterization of Zinc Borate‐Incorporated Recycled PC / ABS Alloys: A Multifunctional, PFAS ‐

ABSTRACT

The development of sustainable, multifunctional polymer systems with enhanced thermal stability and antimicrobial efficacy is critical for sectors with stringent hygiene and safety requirements. In this study, zinc borate (ZnB) was incorporated into a 60% recycled polycarbonate/acrylonitrile‐butadiene‐styrene (PC/ABS) matrix at 5, 10, and 20 wt% via twin‐screw extrusion and injection molding to simultaneously impart antimicrobial activity and improved thermal performance without polyfluoroalkyl substances (PFAS) or organohalogen flame retardants (OFRs). The tensile and flexural modulus of elasticity increased linearly with ZnB content, achieving 28% and 29% improvements at 20 wt%, respectively, while flexural strength remained unchanged. Tensile strength decreased by 7% and elongation at break by 68% at 20 wt% ZnB due to particle agglomeration and weak interfacial adhesion, as confirmed by SEM fracture surface analysis. Thermogravimetric analysis revealed an ash content of 20.8% at 800°C for the 20 wt% ZnB‐incorporated PC/ABS alloy, which was 2.4 times higher than that of neat PC/ABS indicating enhanced char‐forming ability and condensed‐phase flame‐retardant activity. Rheological characterization demonstrated that ZnB incorporation reduced complex viscosity, suggesting favorable processing conditions. Antimicrobial testing against Escherichia coli , Staphylococcus aureus , methicillin‐resistant S. aureus (MRSA), and Candida albicans confirmed increasing antimicrobial activity with ZnB content. This study demonstrates that ZnB serves as a viable PFAS‐free and OFR‐free multifunctional additive for recycled PC/ABS, offering a promising pathway toward next‐generation materials that balance thermal improvement through increased char content, functionality, and environmental responsibility.