Polyhydroxybutyrate/Mica Biocomposites: Influence of Filler Content on the Thermal and Mechanical Properties of PHB

Polyhydroxybutyrate (PHB) is a crystalline and linear biopolymer that is biodegradable and biocompatible. However, due to its high crystallinity, PHB is rigid and brittle, limiting its applications. The brittleness of PHB can be reduced by incorporating reinforcing fillers. In this context, this study aimed to produce biodegradable composites based on a PHB matrix and mica, as a filler. Scanning electron microscopy (SEM) revealed the lamellar structure of mica within the PHB matrix. Fourier-transform infrared spectroscopy (FTIR) confirmed characteristic mica vibrations, while X-ray diffraction (XRD) identified crystalline phases from both PHB and the filler. Differential scanning calorimetry (DSC) demonstrated mica’s effect on crystallinity. Thermogravimetric analysis (TGA/DTG) showed increased thermal stability, with Tonset rising from 144 °C (pure PHB) to 212 °C (PHB/mica 12%) and Tmax from 207 °C to 260 °C. Tensile testing indicated reduced stiffness, from 413 MPa (pure PHB) to 333 MPa (PHB/mica 12%). These findings highlight mica’s role in modifying PHB’s structural, thermal, and mechanical properties, addressing gaps in the literature regarding this composite system.