Poly(limonene) incorporation into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) films via melt blending and compression molding: Enhancement of antioxidant, antimicrobial, and barrier properties

Food packaging materials must combine barrier, mechanical, and functional properties to ensure product protection and extended shelf life, yet many biopolymer films suffer from poor water resistance and high bioactive additive volatility. In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films incorporating oligomeric poly (limonene) (PL) at 5, 10, 12.5, and 15 wt% were prepared via melt blending followed by compression molding. Films were characterized for structural, mechanical, thermal, barrier, and functional properties. Scanning electron microscopy revealed increasing morphological heterogeneity and PL-rich domains at higher PL loadings. No new bands or clearly detectable band shifts were observed by FT-IR, while PL altered the thermal and crystallization behavior of PHBV, reducing melting temperature, crystallinity, and thermal stability. Mechanical performance also decreased with increasing PL content, as indicated by reductions in elastic modulus, tensile strength, and elongation at break. Oxygen permeability decreased by 46% at 10 wt% PL, representing, to the best of our knowledge, the first report of oxygen barrier enhancement using PL in polymer films. Water vapor permeability and moisture content increased with PL concentration, while water contact angle rose from 71 ± 3° to 84 ± 3°, consistent with PL's hydrophobicity. Films also exhibited darker, brown coloration and enhanced UV-barrier properties. Notably, when PL was incorporated, DPPH and ABTS radical-scavenging activities reached 36.1 ± 0.5% and 61.9 ± 0.4%, respectively, while maximum log reductions relative to neat PHBV reached 1.07, 0.80, and 0.98 for Staphylococcus aureus, Escherichia coli, and Aspergillus brasiliensis, respectively. These findings address a relevant literature gap regarding PL incorporation into PHBV films and provide new insights into oligomeric terpene-derived additives in materials with potential for active food packaging applications.