The complex effects of graphene and plant waste/minerals reinforcement on PLA biocomposite performance: an evaluation

The present study investigates the mechanical, thermal, and morphological properties of poly(lactic acid) (PLA)-based biocomposites reinforced with peach pit powder (PP), huntite-hydromagnesite (HH), and graphene nanoplatelets (GNP) as sustainable alternatives to petroleum-based polymers. The biocomposites were fabricated via twin-screw extrusion and hot-press molding and characterised using FTIR, SEM, tensile, flexural and impact tests, DSC, TGA, HDT analysis, and UL-94 vertical burning tests. The incorporation of PP reduced composite density to 1.171 g/cm³ while increasing water absorption due to its hydrophilic structure. HH acted as a nucleating agent, increasing crystallinity to 24.51% and improving thermal resistance, with HDT reaching 89.7 °C. TGA results showed that although PP and HH decreased the onset degradation temperature, they reduced mass loss rate and promoted char formation, contributing to improved thermal stability. However, insufficient dispersion of HH led to failure in UL-94 tests, highlighting the importance of homogeneous filler distribution in flame retardancy. Among the formulations, PLA/PP10/HH5 exhibited optimal performance, achieving a tensile modulus of 1662 MPa and reduced water absorption. Low GNP loadings provided moderate mechanical enhancement, whereas higher loadings caused agglomeration and reduced performance. Overall, PP/HH/GNP reinforcement enhances PLA properties when dispersion and interfacial compatibility are well controlled.