Effect Of ZIF-8 Composite Flame Retardant System On Flame Retardancy Of Polymers

Since the 21st century,with the rapid development of social economy,environmental protection and safety issues have gradually attracted people's attention.Therefore,people are paying more and more attention to the research and development of low smoke,low toxicity,halogen-free and environment-friendly flame retardants.In this paper,a new flame retardant ZIF-8@SiO₂?SiO₂ coated ZIF-8?with core-shell structure was prepared by sol-gel method.Then ZIF-8@SiO₂ was added to epoxy resin?EP?to study its effect on flame retardancy,smoke suppression and thermal stability of EP.ZIF-8@MA?melamine coated ZIF-8?was prepared by using coordination principle and adsorption principle.The ternary composite flame retardant ZMD containing N-Si-Zn was successfully prepared by modifying biomass material diatomite with ZIF-8@MA.The effects of ZMD on flame retardancy,smoke suppression,thermal stability and cell morphology of rigid polyurethane foam?RPUF?were investigated.Zeolitic imidazolate framework-8?ZIF-8?synergistic expansible graphite?EG?flame retardant polyurethane elastomer?PUE?system was designed based on synergistic flame retardant mechanism.The optimum synergistic ratio of ZIF-8 and EG was discussed,and the effects of ZIF-8 and EG on flame retardancy,smoke suppression and thermal stability of PUE were investigated.?1?A material?ZIF-8@SiO₂?with a nuclear shell structure was synthesized to improve the flame retardancy and smoke suppression of epoxy resin?EP?through synergetic catalytic effect.Zeolitic imidazolate framework-8?ZIF-8?was synthesized and its surface was coated with SiO₂ by hydrolyzing tetraethyl orthosilicate?TEOS?.Core-shell structured ZIF-8@SiO₂ was obtained.Then ZIF-8@SiO₂ was added to EP to explore its effect of flame retardancy and smoke suppression on EP composite.The results of the cone calorimeter test showed that the peak heat release rate?PHRR?,total heat release?THR?,smoke production rate?SPR?and total smoke production?TSP?of the material were decreased by 75.9%,38.9%,51.1%and 39.8%,respectively,after 2wt%ZIF-8@SiO₂ was added to EP.Besides,through the analysis of char residue,the mechanism of ZIF-8@SiO₂/EP's flame retardancy and smoke suppression was determined to be due to the physical barrier effect of SiO₂ and the co-effect of SiO₂ and ZnO decomposed by ZIF-8.?2?Firstly,melamine?MA?coated ZIF-8 to prepare ZIF-8@MA with core-shell structure.Then,diatomite was modified by ZIF-8@MA,and the ternary composite ZMD containing N-Si-Zn was successfully synthesized.Finally,ZMD was added into rigid polyurethane foam?RPUF?to investigate its effect on fire safety of RPUF.The results of cone calorimeter and limiting oxygen index?LOI?indicated that ZMD effectively reduced fire hazard of PURF.This was because of the physical barrier effect of diatomite,the co-catalyze char formation in the condensed phase of ZnO produced by decomposition of ZIF-8 and silica in diatomite,and the gas phase effect of MA that enabled RPUF to achieve excellent fire safety.The specific mechanism of fire safety of ZMD for RPUF is also discussed.?3?ZIF-8 was synthesized at room temperature,and then added with expandable graphite?EG?to polyurethane elastomer?PUE?to study their flame retardancy and smoke suppression effect on PUE.The results showed that when the total flame retardant was 3wt%,and the ratio of ZIF-8 and EG was 1:3,it had the best effect on the flame retardancy and smoke suppression of PUE.Compared with pure PUE,the PHRR,THR and the maximum smoke density(D_s,max)values of Z1E3 decreased by83.4%,42.6%and 22.4%,respectively.In addition,the LOI value of Z1E3 increased to 30.2%and its UL-94 vertical burning test reached V-1 rating.This was because ZIF-8 synergized with EG to make the intumescent char layer compact,resulting in improved flame retardancy and smoke suppression of PUE.In addition,the specific mechanism of flame retardancy and smoke suppression is discussed in this paper.