Synthesis And Cure Kinetics Of N,N'-4,4'-Diphenylmethylenebismaleimide Aromatic Diamine Curing Agent For Epoxy Resin

Epoxy resins are widely used in various fields because have the advantages of strong adhesion,chemical resistance and excellent mechanical properties.However,epoxy resins must be used with curing agents to exhibit maximum practical value.Amine curing agents are commonly used,of which aromatic amines are used more widely.It can provide excellent heat resistance,but at the same time there are also shortcomings such as insufficient toughness.Therefore,it is necessary to modify the aromatic amine curing agent.Three new curing agents(BDM-DDM,BDM-MOCA,BDM-DDS)for epoxy resin were synthesized from diaminodiphenylmethane(DDM),3,3'-dichloro-4,4'-diaminodiphenylmethane(MOCA),diamino diphenyl sulfone(DDS)and N,N'-4,4'-Diphenylmethylenebismaleimide(BDM)according to the Michael addition reaction.The addition of BDM reduces the crosslinking density of the epoxy resin curing system and enhances the toughness.Three new curing agents were synthesized,and the structure of the produces was proved by FTIR and LC-MS Characterizations.The curing process of BDM-DDM was investigated by non-isothermal Differential Scanning Calorimeter(DSC)measurement.In order to determine the curing process of epoxy resin,the theoretical initial curing temperature,peak curing temperature,termination curing temperature and curing degree under different curing time were calculated by extrapolation method,determined the appropriate curing process.Curing activation energy E,Linear correlation coefficient R and reaction order n were obtained by Crane equation and Kissinger equation.The epoxy resin E-44 was compounded with the curing agent.The mechanical tests of the E-44/BDM-DDM/DDM,E-44/BDM-MOCA/MOCA and E-44/BDM-DDS/DDS systems were investigated.The thermal stability of the E-44/BDM-MOCA/MOCA curing system was discussed.The dynamic thermodynamic properties of E-44/BDM-DDM/DDM curing system and E-44/BDM-MOCA/MOCA curing system and the flame retardancy of E-44/BDM-MOCA/MOCA were also investigated.The result showed that with the increase of the dosage of modified curing agents,the flexural strength increases first and then begins to show a downward trend,the impact strength and shear strength also have the same trend;with the increase of the dosage of BDM-MOCA,the initial decomposition temperature and T5%decomposition temperature of the curing system were decreased;the storage modulus improved with the increase of the dosage of modified curing agent in the glass state and Tg decreased;with the increase of the dosage of BDM-MOCA,the flame retardancy of the curing system was enhanced.The kinetics of thermal degradation on E-44/MOCA and E-44/BDM-MOCA/MOCA curing system was investigated also.The activation energy of the E-44/MOCA and E-44/BDM-MOCA/MOCA curing system were calculated respectively by two integral methods,Flynn-Wall-Ozawa(FWO)method and Kissinger-Akahira-Sunose(KAS)method.The results showed that activation E-44/BDM-MOCA/MOCA curing system was increased.The activation energy of curing system under different degradation mechanism model was calculated by Coats-Redfern method,and then was determined with the average activation energy which was calculated by FWO and KAS methods.The degradation mechanism of the modified cured epoxy resin had changed,and there were some errors when determining the mechanism of degradation of the curing system.The degradation mechanism of two systems was determined by Malek method.The results showed that both of the two curing systems can be described by the same model.When the conversion rate a is between 0.2 and 0.65,the degradation process of these two curing systems can all be described by the Reaction Order(RO)model.