Chemical and Structural Characterization of Eucalyptus sp. Wood Residue–Poly(vinyl acetate) Composites

This study investigates the production of wood–plastic composites (WPCs) using Eucalyptus sp. residues (RE) and poly(vinyl acetate) (PVAc), aiming to evaluate the chemical, structural, thermal, and morphological characteristics of the resulting composites. The research is motivated by the need to add value to residues from the wood industry in Espírito Santo, Brazil, contributing to more sustainable material utilization. The composites were produced with different proportions of RE (70%, 60%, and 40%) and PVAc (30%, 40%, and 60%) and characterized using thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM). TGA results showed that increasing the PVAc content was associated with a higher initial decomposition temperature and a lower mass loss in the main degradation stage. XRD analysis indicated higher crystallinity in composites with greater RE content, while CP/MAS 13C NMR revealed changes in the organization of the cellulose structure with increasing PVAc content, including a relative increase in signals associated with amorphous regions. FTIR analysis showed changes in the spectral profile and chemical environment of the functional groups as the RE/PVAc ratio varied, although the spectra alone did not conclusively establish the formation of stronger hydrogen bonds. SEM analysis revealed changes in the fracture morphology and matrix distribution with increasing PVAc content. Composites containing 70% RE and 30% PVAc exhibited more pronounced interfacial voids and discontinuities, whereas those containing 40% RE and 60% PVAc showed greater matrix coverage and more continuous polymer-rich regions. However, greater matrix coverage does not, by itself, demonstrate higher interfacial adhesion. Overall, the results demonstrate that variations in RE/PVAc ratio and particle size significantly influence the thermal, chemical, structural, and morphological characteristics of the composites, highlighting the potential of Eucalyptus sp. residues for the production of value-added wood–plastic composites.