Synergistic Flame Retardancy Of Inorganic Flame Retardant In Polyurethane Materials

Since the 21 st century, inorganic flame retardant have received widely concerned due to they could significantly improve the flame retardancy of polymers and environmentally friendly. The pruposes of this paper is to improve the inorganic flame retardant efficiency and take full advantages of it and avoid its disadvantages to explore and design efficient inorganic flame retardant system. In this paper, expandable graphite?EG? and aluminum phosphate?AHP? were added to the rigid polyurethane foam and studied their synergistic flame retardant effect in polyurethane foam. In addition, based on the molecular design, two kinds of hybrids, molybdenum trioxide-loaded graphene?MoO₃-GNS? and cuprous oxide-loaded graphene?Cu₂O-GNS? were prepared via the hydrothermal method and one-pot co-precipitation method, respectively. And the effect of MoO₃-GNS and Cu₂O-GNS on flame retardancy and smoke suppression of polyurethane elastomer?PUE? were studied, respectively. Moreover, the organic modified zirconium phosphate?OZrP? and EG were added to PUE, and the influences of they on thermal stability and flame retardancy of PUE composites were investigated.?1? A series of flame retarding rigid polyurethane foam?RPUF? composites based on expandable graphite?EG? and aluminum hypophosphite?AHP? were prepared by the one-pot method. The properties were characterized by limiting oxygen index?LOI? test, cone calorimeter test, thermogravimetric analysis?TGA?, real time fourier transform infrared spectra?RT-FTIR?, X-ray photoelectron spectroscopy?XPS?, scanning electron microscopy?SEM?, etc. The results indicate that both EG and AHP could enhance the flame retardency of RPUF composites. Besides, the flame retardant effect of EG was better than that of AHP. The results also show that partial substitution of EG with AHP could improve the flame retardency of RPUF, and EG and AHP presented an excellent synergistic effect on flame retardancy. What is more, compared with RPUF/20 EG and RPUF/20 AHP, the heat release rate?HRR? and total heat release?THR? of RPUF/15EG/5AHP were lower. TGA results indicate that partial substitution of EG with AHP could improve the char residue which provided better flame retardancy for RPUF composites. The thermal degradation process of RPUF composites and the chemical component of the char residue were investigated by RT-FTIR and XPS, respectively. And the results prove that RPUF/15EG/5AHP had higher heat resistance in the later stage. Compared with the RPUF composites filled with EG, a better cell structure and mechanical properties were observed with the substitution of AHP for part of EG.?2? Molybdenum trioxide?MoO₃?-loaded graphene?MoO₃-GNS? hybrids and cuprous oxide?Cu₂O?-loaded graphene?Cu₂O-GNS? hybrids were successfully prepared via the hydrothermal method and one-pot co-precipitation method, respectively. Subsequently, the MoO₃-GNS and Cu₂O-GNS hybrids were incorporated into a polyurethane elastomer?PUE? matrix, respectively, and their effects on thermal stability, flame retardancy and smoke suppression properties of PUE were investigated. Thermogravimetric analysis results showed that the incorporation of 2.0wt% MoO₃-GNS or Cu₂O-GNS hybrids efficiently improved the char yield of the PUE matrix. Moreover, the addition of MoO₃-GNS or Cu₂O-GNS hybrids presented excellent flame retardancy and smoke suppression properties of PUE composites, as evidenced by the obvious reduction in their heat release rate, total heat release and smoke density. The improvement in the flame retardancy and smoke suppression properties were mainly attributed to the synergistic effect between the physical barrier effect of graphene sheets and the catalytic charring effect of MoO₃ or Cu₂O.?3? The organic modified zirconium phosphate?OZrP? was prepared by the ion exchange method, which was used to improve the dispersion of ?-ZrP in the polymer matrix. Then, OZrP and EG were added to the PUE to prepare PUE/OZrP/EG composites. The effects of two kinds of flame retardants on the thermal stability and flame retardancy of PUE composites were studied. XRD, FTIR and TGA test results show that the phosphonium salt was successfully intercalated in the interlayer space of ?-ZrP. Cone calorimeter test results show that both OZrP and EG could improve the flame retardancy of PUE composites, and the flame retardant effect of EG is higher than that of OZrP. When the weight ratio of OZrP and EG is 1:3, PUE/OZrP/3EG composite has the lowest heat release rate peak and total heat release. The char residue test results show that the residue char layer of PUE/OZrP/3EG had higher heat resistance.