Improvement of Flame Retardancy and Antidripping Properties of Intumescent Polybutylene Succinate Combining Piperazine Pyrophosphate and Zinc Borate

Abstract

Developing flame-retarded polybutylene succinate (PBS) is a challenging task owing to its high flammability, noncharring, and melt-dripping during burning. In this work, based on the synergistic combination between piperazine pyrophosphate (PAPP) and zinc borate (ZnB), a promising intumescent PBS system was developed as an efficient strategy to impart PBS with improved flame retardancy and antidripping properties. The results showed that PBS/PAPP15%/ZnB5% passed V-0 rating in the UL-94 vertical burning test (3 mm), while only a V-2 rating was achieved for PBS/PAPP20%. Compared to PBS/PAPP20%, the combination of PAPP and zinc borate (ratio of 15:5) led to significant reductions in the peak heat release rate (pHRR, −55%), fire growth rate index (FIGRA, −40%), and maximum average rate of heat emission (MARHE, −47%) evaluated by mass loss cone calorimetry. Meanwhile, the flame retardancy index of PBS/PAPP15%/ZnB5% reached up to 5.18 and the flameout time significantly increased to 1049 s. Fourier transform infrared and solid-state nuclear magnetic resonance analyses were employed to gain insight into the reaction-to-fire mechanism in the condensed phase. The results confirmed the fact that the formation of a crackfree protective intumescent char layer, reinforced by thermally stable inorganic species (boron−zinc phosphates), effectively restricted the heat and fuel transfer between condensed and gas phases, hence resulting in the excellent enhancement in flame retardancy.

Rigid polyurethane foam compounds with excellent fire performance modified by a piperazine pyrophosphate/expandable graphite synergistic system

“…As a Lewis acid, phosphoric acid promoted the decomposition of RPUF to aromatic heterocycles, esters, phenols, and other structures that cyclized or cross‐linked, forming a continuous and dense char 32 . This explains why the residual char of RPUF‐1 was significantly higher than that of pure sample 33 . After adding 20 wt% EG, the T −5wt% and T max values of RPUF‐5 were found to be slightly lower than those of the pure sample because the acidic gas generated by EG decomposition promoted the decomposition of polyurethane molecular chains 12 .…”

“…32 This explains why the residual char of RPUF-1 was significantly higher than that of pure sample. 33 After adding 20 wt% EG, the T À5wt% and T max values of RPUF-5 were found to be slightly lower than those of the pure sample because the acidic gas generated by EG decomposition promoted the decomposition of polyurethane molecular chains. 12 However, the expanded char formed by EG blocked the transfer of heat, thereby increasing the T À50wt% value of RPUF-5.…”

Solid‐state NMR characterization of multi‐component intumescent flame retardant polybutylene succinate formulations

“…Biobased polybutylene succinate (PBS) is a promising polyester that combines strength and biodegradability and shows potential applications in many fields 1 . However, like all other aliphatic polyesters, PBS burns easily, resulting in rapid flame spreading accompanied by the heavy dripping of burning droplets 2 . To address this issue, many solutions have been explored to provide fire protection and flame retardancy toward PBS 3–5 .…”

“…In our previous works, a series of intumescent PBS systems based on IFR (e.g., ethylenediamine phosphate 15,16 and piperazine pyrophosphate 2 ) and zinc borate were studied. It was observed that zinc borate shows synergistic flame retardant effect with IFR in PBS due to the formation of crack‐free and reinforced intumescent char layer with improved cohesion and stability during combustion 17 .…”

“…1 However, like all other aliphatic polyesters, PBS burns easily, resulting in rapid flame spreading accompanied by the heavy dripping of burning droplets. 2 To address this issue, many solutions have been explored to provide fire protection and flame retardancy toward PBS. [3][4][5] According to previous works, intumescent flame retardant (IFR) systems showed great advantages owing to its low smoke and low toxicity, 6,7 and it has become the main strategy to enhance the flame retardancy and anti-dripping performance of PBS.…”