Impact of decabromodiphenyl ethane and ammonium polyphosphate on the coloration and thermal stability of polypropylene

The incorporation of flame retardants and pigments into polypropylene (PP) is essential for meeting fire safety and aesthetic requirements in commercial applications. However, their incompatibility often results in color deviations in the final PP products. In this study, the effect of two representative flame retardants, decabromodiphenyl ethane (DBDPE) and ammonium polyphosphate (APP), on the coloration performance of phthalocyanine blue (PiB) and the thermal degradation behavior of PP were systematically investigated. Color performance was evaluated using reflectance spectra and colorimetric parameters (L*, a*, b*), while thermal stability was assessed by thermogravimetric analysis. The results show that PiB enhance the thermal stability of PP by promoting char formation through a catalytic pathway. In contrast to PP, DBDPE-based BrFP flame retardant exhibits a pronounced antagonistic interaction with PiB, resulting in a significant reduction in the initial decomposition temperature (T_5% decreased by approximately 60 ^oC). APP shows a clear synergistic effect with PiB, leading to an increase in the maximum decomposition temperature. In addition, the intrinsic reflectivity and whiteness of flame retardants, as well as their effect on the crystalline form of PP are not the primary factors governing the color performance of PiB-colored samples. Instead, reflectance variations mainly originate from differences in the microscopic dispersion state of flame retardants, which significantly affect the overall light scattering (S) and absorption (K) behavior in accordance with the Kubelka–Munk theory. while additional effects on pigment dispersion and conjugation length resulted in changes in color saturation and hue. The findings provide valuable insights into the industrial application of pigments and flame retardants in polymers.