Effect of Mixing Time on the Thermal Stability and Activation Energies of NiO/PMMA Nanocomposites

In this study, NiO nanoparticle–reinforced PMMA nanocomposites were fabricated by melt blending, and the influence of extrusion mixing time on structural and thermal properties was examined. Mixing durations of 6 and 12 minutes were applied, and the materials were characterized by X-ray diffraction (XRD) and scanning electron mi-croscopy (SEM). These analyses confirmed the presence of NiO within the PMMA ma-trix and indicated that prolonged mixing promoted particle agglomeration. Thermal behavior was assessed by thermogravimetric analysis (TGA) at heating rates of 5, 10, 15, and 20 °C·min⁻¹, and activation energies of decomposition were calculated using the Kissinger, Tachor, and Augis–Bennett methods. The results showed that extended mixing reduced composite homogeneity and adversely affected thermal stability. In-corporation of NiO nanoparticles decreased both the onset decomposition temperature and the activation energy compared to pure PMMA, facilitating earlier degradation. At 620 K, pure PMMA exhibited an 8% mass loss, whereas the 12-minute blend displayed a 12% loss. These findings highlight the importance of nanoparticle dispersion and processing parameters in governing the degradation behavior of PMMA/NiO nano-composites.