Synthesis And Properties Of Carborane-containing Epoxy Polymers

Epoxy polymers have excellent mechanical properties,adhesive properties,and chemical stability,low curing shrinkage,etc,which widely used in engineering plastics,adhesives,coatings,and composites.However,epoxy polymers have the characteristics of low glass transition temperatures and low-temperature resistance,which limited its application in high-end composite material.To improve the above high-temperature resistance performance,a carborane structure with extremely high rigidity and super aromaticity is introduced into the epoxy polymer,and it is expected to improve heat resistance and thermal stability.In this paper,a variety of carborane-containing epoxy polymers were designed and synthesized by o-carborane bisphenol diglycidyl ether and carborane bisphenol,and the relationship between its structure and high-temperature resistance was studied:Using o-carborane bisphenol diglycidyl ether?succinic acid and 4,4-dicarboxydiphenyl ether as raw materials,tetraphenylphosphonium bromide as a catalyst,propylene glycol methyl ether acetate as a solvent,designed and synthesized Two different main chain structures of carborane poly(hydroxy ester ethers)(P1 and P2).The effect of reaction time and reaction temperature on molecular weight and molecular weight distribution were investigated.P1 and P2 were characterized by infrared spectroscopy and nuclear magnetic resonance,the results showed that P1 and P2 were successfully synthesized.The heat resistance,thermal stability,and thermal oxygen stability of P1 and P2 were evaluated by DSC and TGA.DSC results show that carborane cage structure merges into polyhydroxy ester ethers increases the glass transition temperature(Tg):TGA results show that the char yield of P1 and P2(54.1%and 69.7%)under nitrogen atmosphere has been greatly improved compared with P0,and the carborane can react with oxidize to gain weight under oxygen,lead to char yield(65.7%and 75.6%)of P1 and P2 was further improved in the air atmosphere,which shows that the introduction of carborane can significantly improve the high-temperature resistance of poly(hydroxy ester ethers).2,2-Bis(4-(4-aminophenoxy)phenyl)carborane(BAPPC)and N,N,N',N'-tetraglycidyl-2,2-Bis(4-(4-aminophenoxy)phenyl)carborane(TAPPC)was prepared from o-carborane bisphenol,p-chloronitrobenzene and epichlorohydrin by nitration,amination and epoxidation.The structures of BAPPC and TAPPC were characterized by infrared spectroscopy and nuclear magnetic resonance,the results show that BAPPC and TAPPC were successfully synthesized.TAPPC and AG-80 epoxy resins use BAPPC and DDM as curing agents and BF3 as the catalyst,respectively,to prepare AG-80/DDM/BF3,AG-80/BAPPC/BF3,TAPPC/DDM/BF3 and TAPPC/BAPPC/BF3 four curing systems.DSC and TGA were used to characterize the heat resistance and thermal stability of the four curing systems.The DSC results show that the large volume of carborane restricted the movement of the segments so that no obvious glass transition occurred.TGA results show that,compared with the char yield of AG-80/DDM/BF3 curing system(25.27%),the char yield rate of AG-80/BAPPC/BF3,TAPPC/DDM/BF3 and TAPPC/BAPPC/BF3 curing systems(67.6%,73.5%,and 78.7%)improved significantly at high temperatures.The curing kinetics of TAPPC/DDM/BF3 and TAPPC/BAPPC/BF3 systems were studied by non-isothermal DSC method.Using Kissinger method and FWO method to calculate the average apparent activation energy of TAPPC/DDM/BF3 and TAPPC/BAPPC/BF3 system is 163.83 KJ/mol and 156.66 KJ/mol,which is much higher than that of AG-80/dicyandiamide system.The apparent activation energy is 88.7 KJ/mol.The reaction series calculated by the Crane method are 0.95 and 0.94,respectively.The T-?extrapolation method was used to calculate and combine the characteristics of the system.The curing process of the two systems was 180?/1 h?210?/1 h?250?/2 h.