Nanosilica Driven Structure–Property Behavior in Poly(3‐Hydroxybutyrate‐Co‐3‐Hydroxyvalerate)/Bamboo Biocomposites for Sustainable Packaging

ABSTRACT

Sustainable hybrid biocomposites based on biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), bamboo microparticles, and silica nanoparticles (SNPs) were developed for sustainable packaging applications. PHBV/bamboo composites containing 0, 1, 2, and 3 wt% SNPs were fabricated by melt compounding and compression molding. Bamboo incorporation increased water absorption and thickness swelling due to its hydrophilic nature, whereas nanosilica improved moisture resistance and surface hydrophobicity. The PHBV/bamboo/SNP 2% composite exhibited the lowest water absorption (2.77%), lowest thickness swelling (3.14%), and highest water contact angle (71.25°). X‐ray diffraction and differential scanning calorimetry showed that moderate nanosilica loading modified the crystalline organization of the PHBV matrix, while scanning electron microscopy confirmed improved matrix encapsulation and reduced interfacial defects. The SNP 2% composite exhibited the highest tensile strength (21.28 MPa), tensile modulus (1.12 GPa), and flexural modulus (4.90 GPa), indicating optimum stress transfer. Nanosilica slightly reduced onset degradation temperature but significantly increased char formation, improving flame retardancy: limiting oxygen index increased from 21.7% (PHBV/bamboo) to 24.5% (SNP 3%), with the V‐0 rating improving from V‐2 to V‐0. Overall, the results demonstrate that 2 wt% nanosilica provides the optimum balance between mechanical performance, moisture resistance, and interfacial reinforcement, resulting in enhanced tensile strength, stiffness, and moisture resistance, though at the cost of reduced elongation at break; flame retardancy continued to improve up to 3 wt% nanosilica. These findings highlight the importance of balancing stiffness and ductility when selecting nanosilica loading for PHBV/bamboo biocomposites intended for packaging applications.