Development of Eco‐Friendly <scp>PHBV</scp> Biocomposites Reinforced With Spanish Broom Fibers: From Natural Source to Sustainable Performance

ABSTRACT The development of eco‐friendly polymer composites is a major challenge in the transition toward sustainable materials for advanced applications. In this work, Spartium junceum L . fibers (SBF) were valorized as natural reinforcements for poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) to produce enhanced properties and bio‐based composite systems. Biocomposites were fabricated through melt mixing with different SBF loadings (10, 20, and 30 wt.%), aiming to improve the crystallinity, thermal stability, and mechanical behavior of PHBV while reducing its intrinsic brittleness. Comprehensive characterization of SBF revealed uniform micrometric morphology, a high crystallinity index of 83.2%, and remarkable intrinsic stiffness, with a Young's modulus of around 20 GPa and tensile strength up to 484 MPa, confirming its suitability as a reinforcing phase. XRD demonstrated that the incorporation of 10, 20, and 30 wt.% SBF effectively decreased the crystallinity degree of PHBV‐based biocomposites to 62.1%, 57.5%, and 55.8%, respectively. TGA confirmed that thermal stability was improved despite the reduction in crystallinity, while tensile testing indicated mechanical improvements in stiffness and strength at moderate fiber contents. Overall, the findings demonstrate the potential of PHBV/SBF biocomposites as lightweight materials with improved thermal stability and well‐balanced mechanical properties, offering promising prospects for applications in biomedical devices and sustainable food packaging.