Synthesis Of DOPO-PHBA Reactive Flame Retardant And Its Effect On Properties Of Epoxy Resin With TGIC

Epoxy resins have been known to possess good mechanical properties and excellent adhesive properties,thus have been widely used in industries such as adhesive,coating,laminating,electronic encapsulating materials and composite applications.However,conventional epoxy resins are flammable,making them hard to satisfy some flame retardant requirement,therefore the flame retardancy of epoxy resins is becoming an urgent problem and has attracted more and more attentions from all over the world.The reactive flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide?DOPO?has drawn much attention in recent years.The active P-H bond in its molecule makes it possible to interact with electron-deficient compounds such as Imine group,Phosphazene,Silsesquioxane,Unsaturated bond,Carbonyl to form a variety of DOPO derivatives which can participate in the reaction embedded polymer molecular structure.Unlike other additive flame retardants,reactive DOPO-based flame retardants can form a strong covalent bond with epoxy matrix,avoiding the migration of flame retardants in the whole system,Thus having long-term flame retardancy.However,since the decomposition temperature of DOPO is relatively low,the thermal stability of the DOPO derivative-modified epoxy resin requires to be improved to satisfy the conditions in high temperature.Triglycidyl Isocyanurate?TGIC?as a kind of trifunctional epoxy resin containing triazine ring structure has got excellent heat resistance and thermal stability.However,its processing performance is poor and is expensive.In this paper,a novel reactive flame retardant?DOPO-PHBA?was synthesized by the reaction Between 9,10-dihydro-9-oxa-10-phosphine-10-oxide?DOPO?and p-hydroxybenzaldehyde?PHBA?.Its structure and composition were characterized by FTIR,nuclear magnetic resonance spectroscopy ¹H-NMR and ³¹P-NMR.DOPO-PHBA was compounded with triglycidyl isocyanurate?TGIC?applied to prepare DOPO-PHBA-TGIC/EP composites.The reaction condition was determined by isothermal DSC method,flame retardancy and thermal properties of DOPO-PHBA-TGIC/EP composites were respectively investigated by limiting oxygen index?LOI?,dynamic mechanical analysis?DMA?and thermogravimetric analysis.The mechanism of flame-retardant DOPO-PHBA-TGIC/EP was investigated by SEM and TG-IR.Finally,7628—E-glass fiber was used as the reinforcing material;modified-epoxy resin prepreg was prepared by wet forming method and then the modified epoxy resin copper clad laminate was been made by vacuum hot pressed.The influence of DOPO-PHBA flame retardant on the dielectric properties of epoxy resin was discussed in this paper.The main research contents and conclusions are as follows:?1?DOPO-PHBA is successfully synthesized and the addition of DOPO-PHBA-TGIC can significantly enhance the flame retardancy of EP resin,while the Mass fraction of phosphorus is 0.6wt%,LOI value increases from 24%to32.5%.Additionally,glass transition temperature?T_g?of DOPO-PHBA-TGIC/EP composites with different phosphorus mass fractions are maintained at 200?or higher and the residues at 800?under nitrogen atmosphere are increased.But the initial degradation temperatures and maximum decomposition rates of DOPO-PHBA-TGIC/EP composites are decreased.TG-IR and SEM analysis of char residues reveal that this flame retardant system both satisfy condensed phase flame retardant mechanism and Gas phase flame retardant mechanism,and the incorporation of DOPO-PHBA-TGIC does not impair the physical property of EP resin,while the Mass fraction of phosphorus is 0.42wt%,The flexural strength of DOPO-PHBA-TGIC/EP composite is 125.7MPa,which is 38.7%higher than pure epoxy resin system.?2?Utilizing the non-isothermal Differential Scanning Calorimeter curve,the cure kinetic of this curing system was researched through Málek method,during the analysis of this thermal treatment,kinetic parameters were determined,kinetic model was built and curing behavior under dynamic conditions was predicted.Results indicate that the curing reaction conforms to the?est?k-Berggren model;the reactive activation energy Ea is78.40 KJ/mol and reaction order m and n are 0.30 and 1.30respectively;moreover,the model-predictive curve coincides well with the experimental data,which verifies the accuracy of the model.?3?DOPO-PHBA-2-TGIC/EP with good Comprehensive performance was selected as the resin matrix and 4,4-diaminodiphenylsulfone?DDS?as the curing agent.The gel time of the system is 365s at 180?,145s shorter than pure epoxy resins.While the ratio of resin to acetone was 2:1 and 1:1 respectively,the resin content of prepared prepreg are 53wt%and 46wt%,which are almost the same with pure epoxy resins.?4?DOPO-PHBA-2-TGIC/EP CCL has more excellent dielectric properties,while the resin content are 46wt%and 53wt%respectively,dielectric constant are maintained at 4.78 and 4.65 under the frequency of 1GHz-5GHz,which are decreased compared with the pure EP matrix copper clad laminates?CCL?at the same resin contents,meanwhile,the modified resin CCL has lower dielectric loss.When the content of resin content is 53wt%,the dielectric loss of modified copper clad laminates achieve middle loss level?0.0115?,Which is obviously lower than that of the pure epoxy resin CCL?0.017?.