Study on Flame Retardancy and Interface Performance of Carbon Fiber Reinforced Epoxy Composites Based on a Modified N-P-Si-containing Sizing Agent

A class of N-P-Si-containing synergistic flame retardant T-K, the phosphoric triamide (TEDAP, T) modified with epoxy silane coupling agent KH560 (K) on molecular polarity and structure, was successfully synthesized and utilized as sizing agent of carbon fiber (CF) for surface treatment in carbon fiber reinforced epoxy (CF/EP) composites. Time of flight mass spectrometer (TOF-MS) and Fourier transform infrared spectroscopy (FT-IR) results showed the successful synthesis of T-K and different degrees of oligomerization of T. Scanning electron microscope (SEM) and interlaminar shear strength (ILSS) characterized the surface and interface morphology of CF and relevant composites, indicating that the interface performance was preserved under selected T-K structure. Thermogravimetric (TG) and limiting oxygen index (LOI) testing results reflected the delayed decomposition of CF on T −5% from 450 °C to 700 °C, and increased LOI values of composites from 34% to 44%, illustrating the significant enhancement on flame retardancy in composites by the application of T-K.