Effect of carbon black on improving thermal stability, flame retardancy and electrical conductivity of polypropylene/carbon fiber composites

In this work, carbon black (CB) was introduced into polypropylene/carbon fiber (PP/CF) composite to fabricate multifunctional composites with the improved thermal stability, flame retardancy and electrical conductivity. The morphology investigation showed that one-dimensional CF and zero-dimensional were well dispersed in the PP matrix, and the multistage structure was formed in PP matrix. Compared to pristine PP, the maximum weight loss temperature under air atmosphere was enhanced by 79 °C. The peak value of the heat release rate measured by a cone calorimeter was significantly reduced by 70%, and the total heat release decreased from 198 to 166 MJ/m2. The dramatically enhanced flame retardancy of PP composites was attributed to the formation of a strong three-dimensional (3D) network structure in PP matrix where one-dimensional CF acted as bridges connecting individual zero-dimensional CB, and the accelerated oxidation crosslinking reaction of PP radicals by CB and CF. Furthermore, the electrical conductivity of PP composites was significantly enhanced to 7.8 S/m due to the formation of 3D conductive pathways from CB and CF within the matrix.