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Recent Advances in Boron-Based Flame Retardants
Published in Yuan Hu, Xin Wang, Flame Retardant Polymeric Materials, 2019
Boron phosphate, an inorganic polymer of empirical formula BPO4, can be prepared by heating phosphoric and boric acids to calcining temperature (Petric et al. 2010). It is a white infusible solid that vaporizes at 1450°C–1462°C without decomposition. As opposed to the tri-valency in boric oxide, most of the boron atoms in boron phosphate are tetra-coordinated (i.e., as a BO4− group, Figure 6.5). Boron phosphate is a low cost, low toxicity flame retardant. An amorphous form of boron phosphate is commercially available from Budenheim and Italmatch. Commercially, it is mostly used as an additive in polyphenylene ether alloy. In a PA-PPE alloy, a combination of boron phosphate (5%) and silicone oil (2%) resulted in a V-0 (1.6 mm) rating (Shaw 1998). The use of boron phosphate in conjunction with zinc borate prevents the UL-94 5VA burn-through in PPE/HIPS/SEBS containing triphenyl phosphate (Yin et al. 2003). A patent by Nexans claimed the use of zinc borate or boron phosphate in electrical insulation which is resistant to high temperature such as 1100°C (Demay et al. 2003). The use of boron phosphate as a flame retardant in proton-conducting polyimide for fuel cell membrane application was reported (Cakmakci and Gungor 2013). Recently, it was reported that crystalline boron phosphate can function as a solid acid. In epoxy, it can catalyze the pyrolysis of epoxy at a lower temperature, reduce the release of flammable gas, and promote char formation (Zhou et al. 2014; Li et al. 2017).
Latest trends for structural steel protection by using intumescent fire protective coatings: a review
Published in Surface Engineering, 2020
Muhammad Yasir, Faiz Ahmad, Puteri Sri Melor Megat Yusoff, Sami Ullah, Maude Jimenez
Ullah and Ahmad [173] investigated the effect of zirconium silicate as a filler in an epoxy-based coating containing expandable graphite (EG), ammonium polyphosphate (APP), melamine, and boric acid. Different formulations were developed to study the effects of zirconium silicate on fire resistance and char expansion, morphology and composition. The coatings were tested at 950°C by using the Bunsen burner test for 1 h. The results showed that zirconium silicate enhanced the fire protection performance of IC. Figure 11 shows the improved insulation of the substrate. The microstructure of the char after combustion in furnace was investigated by using the field emission scanning electron microscope (FESEM). The existence of boron phosphate, graphite, boron oxide, boric acid and zirconium silicate in the residual char was confirmed by XRD and FTIR spectroscopy. TGA showed that zirconium silicate enhanced the residual mass of char. Pyrolysis analysis confirmed that IF5-ZS released less gaseous products concentration compared to IF-control coating.