Preparation Of Transition Metal Flame Retardants And Properties In Polyurea Coatings

Polyurea（PUA）is an elastomeric material produced by the reaction of isocyanate component with amino compound component.PUA has excellent physical and chemical properties.It is widely used in national defence and military projects,bridge protection,and building waterproofing.However,PUA is a flammable material,which releases smoke and toxic gases during combustion,threatening human life and producing molten droplets during the combustion process,causing the flames to spread..Transition metals are of interest due to their good catalytic properties.For one thing.The addition of transition metal-based flame retardants to the PUA reduces the toxic gases produced by the PUA by catalyzing the oxidation of the CO released during combustion.For another,it catalyzes the formation of carbon in the PUA to reduce the release of smoke and the production of molten droplets,thus improving the flame retardant properties of the PUA material.In this paper,different transition metal nanohybrids were prepared to investigate their effect on the flame retardant properties of PUA,the details of the paper are as follows.（1）ZnO@MOF@PZS flame retardant was prepared by hydrothermal and polycondensation method to improve the flame retardant performance of PUA materials.Firstly,ZnO nanoflowers played the role as a template for growth of MOF@PZS and zinc source for formation of MOF.PZS was coated on the outside of MOF by polycondensation method.The morphology and structure of composite materials were characterized and analyzed via SEM,XRD,XPS and FTIR.TGA was used to characterize the thermal stability of flame retardants and composite materials.The flame retardant and mechanical properties of the materials were characterized by cone calorimeter and universal testing machine.The cone calorimeter test（CCT）showed that ZnO@MOF@PZS significantly improved the flame retardancy of PUA.The addition of 3%ZnO@MOF@PZS into PUA could result in the peak release rate（PHRR）,total heat release（THR）,total CO production（TCO）and smoke factor（SF）decreased by 28.30%,19.61%,36.65%and 33.28%,respectively.The flame retardant mechanism of the char residue was investigated by SEM and XPS.The mechanical properties test results showed that PUA/ZnO@MOF@PZS had better mechanical properties.（2）Using the cobalt-based nanomaterials with zeolitic imidazolate frameworks（ZIF-67）as a template to prepwere one-dimensional layered hollow nickel-cobalt layered double hydroxide nanocages,the nanocages were assembled on uniformly dwaspersed Ni Mo O₄ nanorods to prepare Ni Mo O₄@Co-Ni LDH,and useγ-aminopropyltriethoxysilane coupling agent for surface modification,and add it to PUA materials to study its flame retardant properties.SEM,XRD,XPS and FTIR were used to characterize and analyze the morphology and structure of composite materials.TGA result showed that the addition of Ni Mo O₄@Co-Ni LDH slightly decreased the initial degradation and the maximum degradation temperature.With the increased loading of Ni Mo O₄@Co-Ni LDH,the char residue increased.The combustion performance investigated by CCT showed that the PHRR,THR and SF of loading with 3.0 wt%Ni Mo O₄@Co-Ni LDH decreased by 34.41%,12.68%and 48.65%,respectively.The mechanical properties test results showed that Ni Mo O₄@Co-Ni LDH/PUA had better mechanical properties.The well-dispersed Ni Mo O₄@Co-Ni LDH not only enhanced the mechanical properties of PUA matrix,but also improved the flame retardant performance of PUA.（3）ZnFe₂O₄@Mg-Al-SDBS LDH（ZF@MASL）flame retardant was prepared by hydrothermal reaction and co-precipitation.Firstly,ZnFe₂O₄ nanoparticles were prepared by hydrothermal reaction.The sludge-like ZnFe₂O₄@Mg-Al LDH was produced at the precipitate through co-precipitation,.It was intercalated and modified with sodium dodecylbenzene sulfonate（SDBS）.SEM,XRD,XPS and FTIR were used to characterize and analyze the morphology and structure of composite materials.TGA was used to characterize the thermal stability of flame retardants and composite materials.The flame retardant and mechanical properties of the materials were characterized by cone calorimeter and universal testing machine.Compared with pure PUA,the CCT results showed that PHRR,THR,and SF were reduced by 20.13%,17.64%and 28.42%,respectively.The flame retardant mechanwasm of the char residue was investigated by SEM and XPS.The mechanical properties test results showed that ZF@MASL/PUA had better mechanical properties.