Development and characterization of hemp-reinforced polypropylene/polyhydroxybutyrate composites

In this study, polypropylene/polyhydroxybutyrate (PP/PHB) blends were developed as a potential alternative to conventionally used polypropylene (PP). In the first stage, polymer blends were prepared by incorporating increasing amounts of PHB into PP, and the optimum PHB content was determined. Environmentally friendly, biopolymer-based, and processable composites were subsequently obtained by adding plasticizers, compatibilizers, corn stalk, and hemp shives at various ratios into the PP/PHB blend via melt compounding. To enhance the interfacial adhesion between the hemp shives and the polymer matrix, alkaline and silane surface modification treatments were applied.The melting and crystallization temperatures of the PP/PHB blends were characterized using Differential Scanning Calorimetry (DSC), and their thermal degradation profiles were investigated through Thermogravimetric Analysis (TGA). Surface morphology and fiber–matrix interfacial interactions were examined using Scanning Electron Microscopy (SEM). The chemical structure of the composites and the influence of additives were analyzed via Fourier Transform Infrared (FTIR) Spectroscopy. The mechanical properties of the composites were evaluated by tensile tests. Biodegradation behavior was assessed by CO₂ evolution and mass-loss measurements to determine biodegradation rates. Consequently, the interaction between PP and PHB was enhanced by the use of plasticizers and compatibilizers, which reduced the disadvantages of PHB, including its high brittleness, low mechanical strength, and poor thermal stability. Additionally, the use of agricultural residues improved the mechanical characteristics of the PP/PHB composites while also making them more biodegradable. As a result of this study, PP/PHB blends enriched with agricultural waste have been given biodegradability and sustainability potential.