Recycled and compatibilized PP-PET composites, reinforced with Angelim Pedra particles

Introduction: The growing demand for sustainable materials has driven the development of polymer composites made from plastic waste and lignocellulosic reinforcements. However, the low compatibility between polypropylene (PP) and polyethylene terephthalate (PET) can limit interfacial adhesion and compromise the performance of the composites. In this study, we evaluated the influence of compatibilization with maleic anhydride-grafted polypropylene (PP-g-MA) on hybrid composites produced with recycled PP, recycled PET and vegetable fiber from Angelim Pedra (Hymenolobium petraeum) particles. Materials and methods: Composites containing recycled PP, 5 or 10% by mass of recycled PET, and 5% Angelim Pedra particles were produced, with and without the addition of 5% maleic anhydride-grafted polypropylene (PP-g-MA). The materials were prepared by step; the Angelim Pedra vegetable fiber and polyethylene terephthalate were sanitized and ground into smaller particles. Both were added as fillers at 5 and 10% by mass to the polypropylene matrix and processed by extrusion using a compatibilizer (PP-g-MA). Subsequently, they were characterized by Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR). Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) and tensile tests according to ASTM D638 standard. Results: Fourier Transform Infrared Spectroscopy (FTIR) analyses indicated the occurrence of chemical interactions between the anhydride groups of the compatibilizer and the hydroxyl groups of the plant fiber. Scanning Electron Microscopy (SEM) micrographs showed improved dispersion of the PET phase and a reduction in interfacial voids in the compatibilized systems. Despite the observed morphological improvements, some formulations containing PP-g-MA exhibited reduced tensile strength. The composite containing 5% PET without a compatibilizer exhibited the best balance between mechanical strength and structural stability. Conclusions: The simultaneous incorporation of recycled PET and Angelim Pedra particles into a recycled PP matrix proved to be feasible for the production of sustainable composites. Compatibilization with PP-g-MA promoted phase interaction and microstructural homogeneity, although the compatibilizer concentration must be optimized to preserve the material’s mechanical performance.