Surface Modification Of Magnesium Hydroxide And Its Flame Retardant Application In EP And EVA Materials

Epoxy resin(EP)and ethylene vinyl acetate(EVA)are widely used in various industries as high-performance polymer materials.However,its high flammability has severely restricted its further application in various fields.To solve this problem,flame retardants need to be added to improve its flame retardancy.However,the flame retardancy of polymer products is facing a key challenge because the safety and efficiency of flame retardants(FR)commonly used in this field are questioned.Magnesium hydroxide(MDH)comprises an important segment in the market of halogen-free flame retardants(HFFR),it can decompose endothermically,release water to cool the combustion and form inorganic protective barrier.However,MDH particles has a bad compatibility with polymers,negatively affecting the interfacial interaction,which reduces the flame retardant efficiency and mechanical strength of the product.For this reason,we need to functionalize the surface of MDH particles to improve or overcome the weaknesses of MDH materials.In this article,first,the transition metal ion and dopamine hydrochloride undergo a complex reaction in an alkaline solution.Dopamine hydrochloride self-polymerizes to form polydopamine coated on the surface of magnesium hydroxide(MDH)to obtain a modified magnesium hydroxide flame retardant filler.Then added modified magnesium hydroxide flame retardant filler and MDH to the EP and EVA matrix to study the mechanical properties of the matrix material.The flame retardant properties of matrix material were investigated by the limiting oxygen index(LOI),UL-94 vertical burning test and cone calorimetry(CCT)test.The specific research content of this paper was as follows:In the first part,MDH@Fe-PDA and unmodified MDH were added to EP matrix according to different mass ratios to prepare a series of flame retardant EP composite materials.Study the flame retardant properties of MDH/MDH@Fe-PDA EP composites with different mass ratios.As compared to pure EP,the p HRR,TSP and p SPR of EP/23 wt%MDH/7 wt% MDH@Fe-PDA composites decreased by 57%,21% and 67% respectively.A TG-FTIR test and SEM test further disclosed that the release of combustible volatiles and the microstructure of char residues during the combustion process of EP composites.The results show that the release of combustible volatiles and toxic gases of EP composites is greatly reduced.At the same time,it is found that the carbon residue has a denser carbon layer structure,which can inhibit the transfer of heat and combustible volatiles.In the second part,since the Fe-PDA modified MDH has a better flame retardant effect.Therefore,this article focuses on the flame retardant effect of other transition metal cobalt,copper,nickel(Co,Cu,Ni)ions complexed with PDA to modify MDH flame-retardant EP.For this reason,we adopt the same modification conditions as the preparation of MDH/MDH@Fe-PDA flame retardant fillers to prepare MDH/MDH@Co-PDA,MDH/MDH@Cu-PDA,MDH/MDH@Ni-PDA as flame retardant.The filler is added to the epoxy resin to obtain a flame retardant epoxy resin composite material containing different transition metal ions.We use the same test methods to study the structure and morphology of MDH/MDH@Co-PDA,MDH/MDH@Cu-PDA,MDH/MDH@Ni-PDA,and the flame retardancy and smoke suppression of epoxy resin composites analysis of properties and carbon residue structure.The results show that EP/MDH/MDH@Fe-PDA composites have the highest LOI value of 29.3%,the highest quality of carbon residue,and the highest impact strength,tensile strength and elongation at break,as well as excellent mechanical properties.In the third part,in order to further study the effect of different transition metals on the flame retardant properties of different types of substrates,we added 50 wt%MDH/MDH@Fe-PDA,MDH/MDH@Co-PDA,MDH/MDH@Cu-PDA,MDH/MDH@Ni-PDA as flame-retardant filler,flame-retardant thermoplastic material ethylene-vinyl acetate copolymer(EVA).The results showed that: different from the flame-retardant epoxy resin matrix,the MDH/MDH@Cu-PDA component has excellent flame-retardant performance for the EVA matrix.Peak release rate(p HRR),total flue gas release(TSP),peak flue gas release rate(p SPR)is the lowest,and the burning time lasts the longest.At the same time,through the carbon residue raman analysis,the EVA/MDH/MDH@Cu-PDA composite has the highest carbon residue strength.But we also found that the mechanical properties of EVA/MDH/MDH@Cu-PDA composites are not the most outstanding.But MDH/MDH@Ni-PDA has the best mechanical properties,with the highest impact strength and elongation at break.