Restricted accessResearch articleFirst published online 2026
Synergistic intumescent flame retardant system based on zinc hydroxystannate and piperazine pyrophosphate for high-impact polystyrene composites with improved fire safety
High-impact polystyrene (HIPS) is widely used in household appliances, electronic equipment casings, packaging materials, and automotive parts due to its excellent dimensional stability, fluidity, electrical insulation, and rigidity. However, its high flammability and significant smoke emission during combustion limit its application in fire-sensitive environments. In this study, a synergistic intumescent flame retardant system composed of hollow cubic zinc hydroxystannate (H-ZHS), piperazine pyrophosphate (PAPP), and melamine polyphosphate (MPP) was developed to improve the fire safety of HIPS composites. Thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 vertical combustion, and cone calorimetry (CCT) were employed to evaluate the thermal stability, flame retardancy, and smoke suppression properties. The optimised composite (30 wt% total flame retardant loading with a PAPP/MPP mass ratio of 7:3 and 2 wt% H-ZHS) achieved a UL94-V0 rating (1.6 mm thickness) and an LOI of 34.3%. Compared to pure HIPS, the peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) decreased by 74.1 ± 3.2%, 20.6 ± 1.8%, and 65.3%, respectively. The synergistic mechanism involved condensed-phase char formation catalysed by H-ZHS and gas-phase flame inhibition by non-flammable gases (e.g. NH3) from PAPP/MPP decomposition. This work provides a practical strategy for developing halogen-free flame-retardant HIPS composites with balanced fire safety and mechanical properties.
WangJBaoLZhaoH, et al.Preparation and characterization of permanently anti-static packaging composites composed of high impact polystyrene and ion-conductive polyamide elastomer. Compos Sci Technol2012; 72: 976–981.
2.
ZhangJWangXLuL, et al.Preparation and performance of high-impact polystyrene (HIPS)/nano-TiO2 nanocomposites. J Appl Polym Sci2003; 87: 381–385.
3.
JuanL. Effect of multiwalled carbon nanotubes (MWNT) on the properties of high impact polystyrene (HIPS). J Nanomater2018; 2018: 1–5.
4.
DingLJiaZSunH, et al.Estimation of mechanical performance, thermal stability and flame retardancy of high-impact polystyrene/surface-modified APP/carboxylic-functionalized MWCNTs nanocomposites. Polymers (Basel)2019; 11: 615–615.
5.
LiuJZhangYPengS, et al.Fire property and charring behavior of high impact polystyrene containing expandable graphite and microencapsulated red phosphorus. Polym Degrad Stab2015; 121: 261–270.
6.
YangDHuYLiH, et al.Flammability and carbonization of high-impact polystyrene/α-zirconium phosphate nanocomposites. Iran Polym J2015; 24: 1069–1075.
7.
BraunUSchartelB. Flame retardant mechanisms of red phosphorus and magnesium hydroxide in high impact polystyrene. Macromol Chem Phys2004; 205(16): 2185–2196.
8.
GenoveseAShanksAR. Structural and thermal interpretation of the synergy and interactions between the fire retardants magnesium hydroxide and zinc borate. Polym Degrad Stab2006; 92: 2–13.
9.
LiuJGuoYChangH, et al.Interaction between magnesium hydroxide and microencapsulated red phosphorus in flame-retarded high-impact polystyrene composite. Fire Mater2018; 42: 958–966.
10.
LiuJGuoYZhangY, et al.Thermal conduction and fire property of glass fiber-reinforced high impact polystyrene/magnesium hydroxide/microencapsulated red phosphorus composite. Polym Degrad Stab2016; 129: 180–191.
11.
HoffendahlCDuquesneSFontaineG, et al.Decomposition mechanism of fire retarded ethylene vinyl acetate elastomer (EVA) containing aluminum trihydroxide and melamine. Polym Degrad Stab2015; 113: 168–179.
12.
GuoJXuFGuoY, et al.Synergistic flame-retardant effect of nano al(OH)3 phosphorus hybrid polymer/polystyrene composite. Mater Rev2018; 32: 2497–2502. 2512.
13.
LiuJLiHChangH, et al.Structure and thermal property of intumescent char produced by flame-retardant high-impact polystyrene/expandable graphite/microencapsulated red phosphorus composite. Fire Mater2019; 43: 971–980.
14.
LiuJYuZShiY, et al.A preliminary study on the thermal degradation behavior and flame retardancy of high impact polystyrene/magnesium hydroxide/microencapsulated red phosphorus composite with a gradient structure. Polym Degrad Stab2014; 105: 21–30.
15.
LuHWilkieAC. Study on intumescent flame retarded polystyrene composites with improved flame retardancy. Polym Degrad Stab2010; 95(12): 2388–2395.
16.
LiuJZhangYGuoY, et al.Effect of carbon black on the thermal degradation and flammability properties of flame-retarded high impact polystyrene/magnesium hydroxide/microencapsulated red phosphorus composite. Polym Compos2018; 39: 770–782.
17.
ShenRHatanakaCLAhmedL, et al.Cone calorimeter analysis of flame retardant poly (methyl methacrylate)-silica nanocomposites. J Therm Anal Calorim2017; 128: 1443–1451.
18.
CaoLDengSHeZ, et al.Effects of carbon nanotube on mechanical, crystallization, and electrical properties of binary blends of poly(phenylene sulfide) and polyphthalamide. J Therm Anal Calorim2016; 125: 927–934.
19.
YanLXuZZhangJ. Flame retardant and smoke suppression mechanism of multi-walled carbon nanotubes on high-impact polystyrene nanocomposites. Iran Polym J2016; 25: 623–633.
20.
DingLJiaZSunH, et al.Estimation of mechanical performance, thermal stability and flame retardancy of high-impact polystyrene/surface-modified APP/carboxylic-functionalized MWCNTs nanocomposites. Polymers (Basel)2019; 11: 615–615.
AttiaFNAfifiAHHassanAM. Synergistic study of carbon nanotubes, rice husk ash and flame retardant materials on the flammability of polystyrene nanocomposites. Mater Today Proc2015; 2: 3998–4005.
23.
JunMXYuSXChuanL, et al.Preparation of poly(phosphoric acid piperazine) and its application as an effective flame retardant for epoxy resin. Chin J Polym Sci2018; 36: 655–664.
24.
XiaoXHuSZhaiJ, et al.Thermal properties and combustion behaviors of flame-retarded glass fiber-reinforced polyamide 6 with piperazine pyrophosphate and aluminum hypophosphite. J Therm Anal Calorim2016; 125: 175–185.
25.
LiLLHuangYTTangW, et al.Synergistic effect between piperazine pyrophosphate and melamine polyphosphate in flame retardant coatings for structural steel. Polymers (Basel)2022; 14: 3722.
26.
BraunUSchartelBFicheraMA, et al.Flame retardancy mechanisms of aluminium phosphinate in combination with melamine polyphosphate and zinc borate in glass fibre reinforced polyamide 6,6. Polym Degrad Stab2007; 92: 1528–1545.
27.
ZhaYHuiWYuanL, et al.Synergistic effect between piperazine pyrophosphate and melamine polyphosphate in flame retarded glass fiber reinforced polypropylene. Polym Degrad Stab2021; 184: 109477.
28.
HuZZhongZQGongXD. Flame retardancy, thermal properies, and combustion behaviors of intumescent flame-retardant polypropylene containing (poly) piperazine pyrophosphate and melamine polyphosphate. Polym Adv Technol2020; 31: 701–710.
29.
ChenTXiaoXWangJ, et al.Fire, thermal and mechanical properties of TPE composites with systems containing piperazine pyrophosphate (PAPP), melamine phosphate (MPP) and titanium dioxide (TiO2). Plast, Rubber Compos2019; 48: 149–159.
30.
ZhongYHLiMLZhangLC. Adding the combination of CNTs and MoS into halogen-free flame retarding TPEE with enhanced the anti-dripping behavior and char forming properties. Thermoch Acta2015; 613: 87–93.
31.
LyuXZhangHYanY. Effect of expandable graphite and molybdenum trioxide in nitrogen/phosphorus synergistic system on acoustic performance and fire safety in rigid polyurethane foam. J Appl Polym Sci2022; 139: 52488.
32.
KimJSSongJELimD, et al.Flame-Retardant mechanism and mechanical properties of wet-spun poly (acrylonitrile-co-vinylidene chloride) fibers with antimony trioxide and zinc hydroxystannate. Polymers (Basel)2020; 12: 2442.
33.
SuXYiYTaoJ, et al.Synergistic effect of zinc hydroxystannate with intumescent flame-retardants on fire retardancy and thermal behavior of polypropylene. Polym Degrad Stab2012; 97: 2128–2135.
34.
ChenSLLiJYuanYJ, et al.Zinc hydroxystannate coated by polyphosphazene to improve the fire safety and suppress the smoke of epoxy resin. Prog Org Coat2024; 186: 108041.
35.
MaDPZhangLHuJT, et al.Preparation and gas-sensitive properties of hollow Zn2SnO4/SnO2 nano-cubes. Inorg Chem Commun2022; 141: 109507.
36.
LiuLZhuMShiYQ, et al.Functionalizing MXene towards highly stretchable, ultra tough, fatigue and fire-resistant polymer nanocomposites. Chem Eng J2021; 424: 130338.
37.
LiuJHZhangXQLiuSH, et al.Char structure and charring mechanism of phosphazene-based epoxy resin during combustion. Polym Degrad Stab2022; 200: 109927.
38.
SunXMLiZWOisikD, et al.Superior flame retardancy and smoke suppression of epoxy resins with zinc ferrite@polyphosphazene nanocomposites. Composites Part A2023; 167: 107417.
39.
LingMYYinNNChenYF, et al.Construction of polylactic acid-based flame retardant composites by zinc oxide and bamboo carbon. Carbon Lett2024; 34: 665–675.
