A phosphorous/nitrogen/silicon containing diphenylphosphoramide silicon oil toward effective flame retardancy for polycarbonate with comparable mechanical properties

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Silicone diphenylsulfonate (SDPSF) was synthesized via nucleophilic substitution reaction between dihydroxyalkyl‐terminated silicone oil and benzene sulfonyl chloride, and its chemical structure was confirmed by Fourier transform infrared (FTIR) and 1H NMR. The effect of SDPSF on the flame retardancy, thermal stability, combustion behavior, and mechanical properties of PC/SDPSF blends were investigated. The PC/2 wt% SDPSF blend achieved the UL‐94 (3 mm) V‐0 rating and limiting oxygen index value of 30.3% together with the lowest values of the total heat release (32.2 MJ/M2), peak heat release rate (239.5 kW/M2), CO production (0.48 kg/kg), and fire growth index (1.09 kW/s·m2). It demonstrated that the SDPSF improved evidently the flame retardancy and fire safety of the polycarbonate (PC) matrix. The blend also gave a slightly reduced tensile strength (60.0 MPa) and notched impact strength (57.0 kJ/m2). The TG‐FTIR spectra of the pyrolysis gases demonstrated that the SDPSF promoted the decomposition of PC matrix on advance to release much more nonflammable gases in the early combustion process, meanwhile, the analysis of the char residues confirmed that the SDPSF facilitated the formation of compact and continuous layers with higher graphitization degree to isolate the transfer of heat and combustible volatiles.

Section: Introductionmentioning

confidence: 99%

A silicone diphenylsulfonate for improving the flame retardancy of polycarbonate

Song

Luo

et al. 2022

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A nitrogen‐rich DOPO‐based phosphoramide for improving the fire resistance of polycarbonate with comparable mechanical property

Cai,

Jiang,

et al. 2023

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A nitrogen‐rich DOPO‐based phosphoramide (DPAPZ) was synthesized using aminopyrazine and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as raw materials, and blended with polycarbonate (PC) through melting method. The chemical structure of DPAPZ was validated by FTIR, 1H NMR and 31P NMR. The presence of DPAPZ endowed PC/DPAPZ composites with better fire safety and smoke suppression. With the incorporation of 6 wt% DPAPZ, PC/DPAPZ‐6 composite reached UL‐94 V‐0 rating and 30.2% of limiting oxygen index value. Simultaneously, the peak of heat release rate and total heat release of PC/DPAPZ‐6 were reduced by 44.8% and 47.0% as compared with the pure PC, respectively. The DPAPZ displayed bi‐phase flame retardant roles. In the gas phase, the decomposition of DPAPZ released phosphorus‐containing free radicals acting as the quencher of reactive H·/OH· and nonflammable NH3 diluting O2/combustible volatiles. In the condensed phase, the phosphorus‐containing components were dehydrated into metaphosphoric acid or polymetaphosphate covering the surface to protect the PC matrix from further combustion, and to promote the formation of a dense carbon layer to interrupt the transmission of O2 and volatiles between the combustion zone and the inner. The tensile strength of the composites displayed almost no change but the elongation at break decreased slightly with the addition of DPAPZ.

Enhancing the flame retardancy of polycarbonate through the synergistic effect of 1,3‐Benzenedisulfonate acid dipotassium salt and phenyl polysiloxanes

Zhang,

Qiao

et al. 2024

As the application of polycarbonate (PC) in various fields continues to expand, the requirements for its flame retardancy are becoming increasingly stringent. To enhance the flame retardancy of PC, employing multi‐element synergistic effects and developing novel flame retardants are considered as vital strategies. This work introduces a blend of 1,3‐Benzenedisulfonic acid dipotassium salt (KSP) and three types of phenyl polysiloxanes, namely Octaphenylcyclotetrasiloxane (P4), Octaphenylsilsesquioxane (OPS), and ladder‐like Polyphenylsesquioxane (L‐PPSQ), into PC to create composites. The thermal stability and combustion properties of these composites were characterized using thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests. Composites with phenyl polysiloxanes achieved a UL‐94 V‐0 flame retardant rating for 1.6 mm thickness sample and reduced the peak heat release rate by 30%–45%. PC composites with 3% OPS and 0.03% KSP achieved optimal performance, howing a LOI of 34.5%, a 45.4% reduction in peak heat release, and a 40.5% reduction in total smoke release. The flame‐retardant mechanism was analyzed using scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and pyrolysis‐gas chromatography‐mass spectrometry (Py‐GC‐MS).