Improved thermal behavior of polypropylene polymer loaded with bulk and nanoscale Bi₂O₃/CuO composite

This study investigates the structural, vibrational, morphological, and optical properties of bulk and nanoscale Bi₂O₃ and CuO oxides and their composite, which were prepared via high-speed ball milling at different times (20, 40, 60, and 80 min). According to X-ray diffraction analysis, Bi₂O₃ and CuO preserved their monoclinic crystal structures. However, the increase in milling time resulted in peak broadening, smaller crystallite sizes, and higher microstrain. FTIR revealed consistent Bi-O and Cu-O vibrational modes, with slight shifts to higher wavenumbers as crystallite sizes decreased. PL investigations revealed a significant quenching effect with prolonged milling, which was attributed to an increase in oxygen vacancies and structural defects, leading to enhanced related emissions. The EDX verified the elemental compositions, and SEM micrographs demonstrated how increasing milling time transformed the bulk agglomerates into finer and more uniform nanoparticles. In both bulk and nanocomposites, the 70 wt.% Bi₂O₃ and 30 wt.% CuO combination displayed encouraging optical characteristics, indicating potential for usage in optoelectronic devices. The effect of bulk and nanofillers on the thermal and structural properties of polypropylene (PP) composites is also studied in this research. According to thermogravimetric analysis studies, the resistance to heat degradation significantly improves with an increase in filler content. The highest bulk (B20) and nanofiller (N20) composites had commencing breakdown temperatures (T_5%) of 381 °C and 387 °C, respectively, compared to 324 °C for pure PP. Due to improved filler dispersion and interfacial contact, nanocomposites exhibited advanced thermal barrier performance with higher activation energies and a more consistent and regulated degradation profile. Particularly in nanocomposites, DSC data showed a little change in the melting onset and peak temperatures along with an increase in the degree of crystallinity and enthalpy of fusion. The outcomes demonstrate that although both types of fillers enhance thermal behavior, nanofillers provide better improvements due to their greater surface area and stronger interfacial effects. Incorporating nanoscale fillers into polymer nanocomposites is crucial for improving thermal stability, heat resistance, and crystallinity because they facilitate efficient heat transfer and function as powerful nucleating agents inside the polymer matrix.