Effect of ZnO surface modification on mechanical strength and biodegradability of polycaprolactone composite materials

Polycaprolactone (PCL) is a biodegradable polyester with significant potential in biomedical and packaging applications; however, its utility is often constrained by suboptimal mechanical strength and a relatively slow degradation rate. This research investigates the enhancement of PCL properties through the incorporation of zinc oxide (ZnO) nanoparticles, focusing on the pivotal role of nanoparticle surface modification. ZnO nanoparticles were surface-modified using 3-aminopropyltriethoxysilane (APTES) to improve their dispersion and interfacial compatibility with the PCL matrix. Neat PCL, PCL/unmodified ZnO (PCL/U-ZnO), and PCL/APTES-modified ZnO (PCL/M-ZnO) composites with varying filler loadings (1, 3, and 5 wt%) were fabricated via solution casting. Comprehensive characterization revealed that APTES modification successfully grafted onto ZnO surfaces, leading to significantly improved nanoparticle dispersion and interfacial adhesion within the PCL matrix, as evidenced by electron microscopy and spectroscopic analyses. Consequently, PCL/M-ZnO composites exhibited superior mechanical performance; for instance, PCL/3%M-ZnO demonstrated a tensile strength of 35.2 MPa and a Young's modulus of 558 MPa, representing approximately 46% and 39% increases, respectively, compared to PCL/3%U-ZnO. Biodegradation studies under hydrolytic, enzymatic, and soil burial conditions indicated that surface modification influenced the degradation profiles. PCL/M-ZnO composites generally showed accelerated enzymatic degradation (e.g., 36% weight loss for PCL/3%M-ZnO vs. 21% for neat PCL after 14 days with lipase) and a nuanced behavior in soil, suggesting that tailored interfacial properties can modulate the environmental fate of PCL composites. These findings underscore the efficacy of ZnO surface modification as a strategy to develop high-performance PCL-based materials with tunable mechanical and biodegradable characteristics.