Construction of an efficient ternary flame retardant system for rigid polyurethane foam based on bi‐phase flame retardant effect

Abstract

The flame-retardant rigid polyurethane foams (RPUF) were prepared by using modified ammonium polyphosphate (MAPP) combined with expandable graphite (EG) and dimethyl methylphosphonate (DMMP). The thermal stability, flame retardant property, and mechanical property of flame-retardant RPUF were evaluated based on thermogravimetric analysis (TGA), limiting oxygen index (LOI) test, cone calorimetry tests, scanning electron microscopy (SEM) and compressive strength tests. The results showed that an efficient ternary flame retardant system, DMMP/EG/MAPP, for rigid polyurethane foam was constructed. When the ratio of DMMP/EG/MAPP was 4/12/4, the cell size of RPUF composite was the most homogeneous, and the LOI value of RPUF composite reached 31.9%. The peak heat release and total smoke release value decreased to 97 kW/m 2 and 347 m 2 /m 2 , respectively. The RPUF composites with 4%DMMP/12%EG/4%MAPP exhibited the best flame retardant property because DMMP/EG/MAPP played great free radical quenching effect in the gas phase by releasing the POÁ and PO 2 Á free radicals during the whole combustion process. Meanwhile, the compact char layer with "connected worm-like" structure exerted barrier effect in the condensed phase.

Effect of two‐dimensional zeolitic imidazolate frameworks‐L on flame retardant property of thermoplastic polyurethane elastomers

“…In order to characterize the graphitization degree of the sample, the ratio of peak area of D (1364 cm −1 ) peak and G(1594 cm −1 ) peak of Raman spectrum is usually used to indicate the graphitization degree of the sample. The smaller the I D /I G value is, the higher the graphitization degree of the sample will be 31 . Pure TPU I D / I G is 2.51, after different ZIF‐L were added, they have different degrees of lower ratio, the lowest I D /I G value of TPU2 is 2.19, it showed that the metal oxide produced by the decomposition of three ZIF‐L can promote the formation of graphite carbon in a certain extent and Co have better catalytic effect, which can improve the flame retardant performance of composite materials.…”

Preparation of Flame-Retardant Polyurethane and Its Applications in the Leather Industry

“…Expandable graphite (EG), it should be noted, has been widely applied in polymer as flame retardants, especially in rigid polyurethane foam (RPUF) [ 24 , 25 , 40 , 41 , 42 , 43 ], due to its low toxic, abundance, and high flame-retardant efficiency. The flame-retardant mechanism of EG is that it can immediately expand (150~300 times) at relatively low temperature, and then form a worm-like protective char layer in the condensed phase, which is an effective barrier to prevent heat and mass transfer [ 24 , 42 , 43 ]. However, the loose “graphite worm” residues are easy to collapse, which hinders the further improvement of the flame-retardant efficiency of EG.…”

“…However, the loose “graphite worm” residues are easy to collapse, which hinders the further improvement of the flame-retardant efficiency of EG. Therefore, EG was usually used with other flame retardants, such as inorganic hydrated compounds [ 24 , 25 ], P/N/Si-containing organic compounds [ 40 , 41 , 42 , 43 ].…”

“…The results demonstrated that the addition of 25% DPPM could enhance the oxygen index of flame-retardant PU to 29.5% [39]. Expandable graphite (EG), it should be noted, has been widely applied in polymer as flame retardants, especially in rigid polyurethane foam (RPUF) [24,25,[40][41][42][43], due to its low toxic, abundance, and high flame-retardant efficiency. The flame-retardant mechanism of EG is that it can immediately expand (150~300 times) at relatively low temperature, and then form a worm-like protective char layer in the condensed phase, which is an effective barrier to prevent heat and mass transfer [24,42,43].…”

Effects of Various Types of Expandable Graphite and Blackcurrant Pomace on the Properties of Viscoelastic Polyurethane Foams

“…Therefore, in recent years, researchers have focused on finding synergistic effect of expandable graphite (EG) with other additive flame retardants [ 40 , 41 , 42 ] or nanofillers [ 43 , 44 , 45 ]. The main mechanism to improve the flame resistance is to increase the char yield [ 46 , 47 , 48 ].…”