Preparation And Properties Of Heat-resistant And Fire-resistant Epoxy Resin And Its Adhesive Film

Epoxy resin is the most widely used type of resin due to its excellent mechanical properties,good adhesion and corrosion resistance,especially the low shrinkage rate and low gas release during the curing process.In recent years,the position occupied by polymer adhesives in today's society is becoming more and more important.In order to solve the increasingly serious energy problem,adhesives used in various lightweight structures have become a research hot spot.Film adhesives have the advantages of convenient transportation and storage,simple operation during use,and high efficiency,and have gradually begun to replace traditional adhesives.Epoxy resin itself does not have any film-forming properties,and has extremely flammable properties,which limits its development in the field of adhesives.In this paper,phenolic epoxy resin(EPN)was used as the matrix and modified with toluene diisocyanate to give the epoxy resin film-forming properties.At the same time,a latent flame-retardant curing agent synthesized from Flame retardant DOPO and imidazole was used to improve the flame-retardant properties of the film.Finally,thermoplastic materials,rigid particles,and fibers were added to improve the toughness of the film.The most experiment contents and results are shown below:(1)Toluene diisocyanate(TDI)was used to react with EPN to introduce a flexible oxazolidinone ring structure into the resin matrix.By increasing the chain length of the main chain of the polymer chain resin and increasing the molecular weight,the synthesized modified phenolic epoxy resin(EPOD)was given film-forming properties.At the same time,the oxazolidinone ring structure with excellent thermal stability could also bring better heat resistance,and the flame retardant performance had been improved to a certain extent.The T₅temperature of EOPD was 337.18°C in air and 364.95°C in nitrogen,which were increased by 70.8%and 133.9%respectively compared to the reference sample;the limiting oxygen index was increased from 20.3 to 21.5,and the dripping during combustion was improved too.At the same time,when the resin burned,the heat release rate of the material was greatly reduced without reducing the total heat release,and the ignition time and residual rate were also improved.(2)DOPO flame retardant was used to modify imidazole curing agent to synthesize a new reactive flame retardant curing agent DMH.The cured samples had excellent flame retardant abilities,especially after curing the modified phenolic epoxy resin matrix,it could not only endow the resin matrix with inherent flame retardant properties,but also synergize with the oxazolidinone structure in the heat-resistant resin matrix.Compared with ordinary epoxy resins,the flame retardant properties of the cured samples were further improved.At the same time,the resin used the flame-retardant curing agent also maintained high heat resistance.The limiting oxygen index(LOI)of the 5%DMH/EP cured sample reached 27.8%,and the 5%DMH/EPOD increased to 31.8%,and passed the UL-94V-1 level;10%DMH/EPOD,15%DMH/EPOD reached the LOI values of 32.2%and 34.6%,and both passed the UL-94V-0 rating.At the same time,the T₅temperature of DMH/EPOD under air and nitrogen atmosphere could reach 366?and 348?,which was 75.1%and 76.6%higher than that of DMH/EP system.(3)The prepared EPOD was used as the resin matrix and DMH was used as the curing agent.At the same time,the viscosity and toughness of the adhesive film during curing were adjusted by adding thermoplastic polyethersulfone(PES)material and rigid particle aluminum powder and Basalt fiber(BF).The influence of each component on the adhesive performance of the film was also explored.The optimal addition amount of DMH,BF,PES and aluminum powder was 10%,20%,8%and15%.The maximum lap shear strength of the adhesive film bonding sample could reach 25.675MPa,and the maximum average roller peel strength could reach 47(N·mm)/mm.PES,aluminum powder,and BF could effectively inhibit the propagation of cracks through their respective toughening mechanisms,and improved the toughness and bonding performance of the material.