Ultra-tough, photothermal healing and fire safety polystyrene/hydroxylated black phosphorus-triazine COF composites

Devoting to coping with safety risk spreading with polymers, this work achieves dramatic synergistic im-provements in composite toughness, photothermal healing, and fire safety through a novel targeted modification strategy for black phosphorus (BP). In detail, we herein use the emerging 2D BP as a template for in-situ growth by covalent triazine framework (HBP-CTF). Incorporating gradient increased HBP-CTF (1, 2, 4 wt%) into polystyrene (PS), the elongation at break increased by 61.59%, 74.60% and 62.82% for composites, respectively. This is attributed to the synergistic effects of two components of HBP-CTF as stress conduction unit and interface and dispersion improver, respectively. Furthermore, PS/HBP-CTF composites achieve photothermal healing over 96% in strength and elongation at break induced by outstanding photothermal properties (linearly quantifiable, R-2 > 0.997). Noted, PS/HBP-CTF2.0 and PS/HBP-CTF4.0 achieve record reductions of 61.77% and 69.85% in peak heat release rate, accompanied by dramatically reduced total heat release. Taking the pyrolysis of HBP-CTF as an index, this work proposes the idea of using P-4 as the key product to monitor and distribute gas phase effects for BP-based flame retardants. The hybridization of CTF to HBP promotes the slow and continuous release of P-4 in the gas phase, revealing the structure and composition of char that cross-linking P and N. This work provides strategies for synergistically overcoming composite brittleness, crack failure, and high flammability, paving the way for practical applications.

Automated summary

This work achieves significant improvements in composite toughness, photothermal healing, and fire safety through a novel targeted modification strategy for black phosphorus. The incorporation of HBP-CTF into polystyrene results in increased elongation at break in the composites, attributed to its stress conduction and interface and dispersion improvement properties. The PS/HBP-CTF composites show excellent photothermal healing properties and achieve record reductions in peak heat release rate, indicating their potential for practical applications in overcoming brittleness, crack failure, and high flammability.