Tunable thermal, flame retardant and toxic effluent suppression properties of polystyrene based on alternating graphitic carbon nitride and multi-walled carbon nanotubes

Significant improvements in thermal and flame retardant properties of polymeric materials at low loadings hold tremendous promise for fire safety materials. In the present work, a highly effective graphitic carbon nitride/acidized multi-walled carbon nanotube (g-C₃N₄/aMWCNT) bilayer was deposited on a PS sphere for reducing its fire hazards. The PS sphere allowed the intimate assembly of the g-C₃N₄/aMWCNT bilayer on its surface through electrostatic interactions. Structural and morphological characterization revealed the successful assembly of PS/g-C₃N₄/aMWCNT systems. Enhanced thermal stability and flame retardancy (e.g. a decrease of ca. 45% and 47% in HRR and THR, respectively) were obtained for the ternary assembled systems instead of the binary materials. The phenomena were caused by two reasons: g-C₃N₄/aMWCNT bilayers induced the construction of the "tortuous path" which impeded the permeation of heat and the escape of pyrolysis volatile products; on the other hand, stacked g-C₃N₄ nanosheets or thermolabile aMWCNTs with an uncompact network structure led to poor thermal stability and fire resistance. Thus, this work paves a potential pathway to design efficient assembled fire-retardant systems for fire safety.