Flame retardancy and smoke suppression of silicone foams with microcapsulated aluminum hypophosphite and zinc borate

Abstract

The flame‐retardant microcapsules were successfully fabricated with an aluminum hypophosphite (AHP) core. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) were used to verify that AHP was encapsulated in the microcapsules, and thermogravimetry analysis showed that microencapsulated AHP (MAHP) possessed higher thermal stability than that of AHP. Then, a flame‐retardant and smoke suppression system for silicone foams (SiFs) was obtained through a synergistic effect of MAHP and zinc borate (2ZnO·3B2O3·3.5H2O). The mechanical properties, flame retardance, and smoke suppression of SiFs with MAHP and zinc borate were tested using the tensile test, limiting oxygen index (LOI) test, UL‐94 test, and cone calorimeter test. The mechanical properties indicated that the tensile strength and elongation at break of SiFs could evidently improve with the incorporation of MAHP. Compared with pure SiF, SiF8 with 4.5‐wt% MAHP and 1.5‐wt% zinc borate could achieve an LOI value of 30.7 vol% and an UL‐94 V‐0 rating, the time to ignition amplified almost six times, the peak heat release rate and total heat release were 51.10% and 46.00% less than that of pure SiF, respectively, the fire performance index increased nearly 13 times, and the fire growth index value was only 13.18% of pure SiF. Moreover, the partial substitution of zinc borate imparted a substantial improvement in both flame retardancy and smoke suppression. Especially, the peak smoke production rate and total smoke production of SiF8 were merely 38.46% and 38.84% of pure SiF.

Flame retardant rigid polyurethane foam composites based on iron tailings and aluminum phosphate: A novel strategy for utilizing industrial solid wastes

“…The peak of CO generation in RPUF-1 was about 0.03 g/ s, while the yield of RPUF-6 was significantly increased with the addition of AHP, which may because the oxidation of phosphine generated by AHP resulted in the hypoxic atmosphere and inhibited full oxidation of carbon element in RPUF. 40 When ITs was combined with AHP and added into RPUF, RPUF-4 possessed significantly decreased CO yield compared with RPUF-6, implying excellent toxicity reduction performance of ITs.…”

Effect of two boron compounds on smoke‐suppression and flame‐retardant properties for rigid polyurethane foams

“…A comparison of data from other literature on smoke‐suppression strategies of RPUF is listed in Table S1. Among those strategies, boron compounds such as zinc borate (ZB), 20,21 boron phosphate (BP) 22,23 and so on were often chosen to be utilized in RPUFs. ZB is a multifunctional flame retardant containing different proportions of zinc and boric acid oxides 24 .…”

Preparation, characterization and fire resistance evaluation of a novel ceramizable silicone rubber composite

“…17,18 Hu et al 19 reported the combining effect of ATH, ammonium polyphosphate, and mica to improve the flame retardancy and fire prevention of silicone rubber ceramifying composites. Kang et al 20 studied a synergistic effect between microcapsulated aluminum hypophosphite and zine borate used in silicone foams, and found it exerted excellent smoke suppression and flame retardant properties.…”