| Dual-curing epoxy system can react some other curing behavior as well as the epoxy ring opening reaction which the conventional epoxy resin can do.There is a new method for epoxy resin modification that is introduction of other reactive groups to epoxy resin through the resin design so that curing agents can react with resin in two different curing mechanisms to adjust the performance and characteristics of epoxy resin. Dual-curing technology is an important means of curing, which can change the cross-linking points, the crosslink density, the heat resistance of the epoxy resin.In this paper, furan group containing the conjugated double bonds was introduced to bisphenol which was used in synthesis of epoxy resin with conjugated diene. There exist both the ring opening esterifying reaction of the epoxy ring and anhydride and Diels-Alder reaction of double bond in the resin and furan ring of anhydride, which are called dual-curing technology. The latter reaction creates a multi-ring structure, so that it not only improve the cross-linking density and heat resistance of the materials, but also add a new way of double-curing method to curing research of epoxy resins. The following are the main contents of this paper: Bis(4-hydroxy-3,5-di-methylphenyl)-furylmethane was synthesized by the condensation reaction using 2,6-xylenol and furfural as starting materials, sodium hydroxide as catalyst. The influence of molar ratio 2,6-xylenol/furfural, catalyst dosage, reaction temperature and reaction time on bisphenol yield was studied in experiment. The optimum reaction conditions were determined as follows:2.2:1 of molar ratio 2,6-xylenol/furfural,1:0.11 of molar ratio 2,6-xylenol/sodium hydroxide, the reaction temperature 65℃and the reaction time 5h. Under that conditions, the product yield could reach 61.7%.The structure of the product with melting point of 151.1℃and purity of 99.52% was confirmed by FTIR,1H-NMR and MS.Epoxy with furan group was synthesized by a two-step method, and characterized by NMR and FTIR. The viscosity of epoxy resin was tested by rotational viscometer. The result of viscosity determination draws a conclusion that the flow activation energy of 85.95KJ/mol of epoxy resin with furan group is higher than that of 73.45 KJ/mol of E51 resin, in other words the synthetic resin is more sensitive to temperature. The epoxy value of this epoxy resin is 0.38mol/100g tested by hydrochloric acid-acetone method. Also the epoxy resin could be well soluble in most alcohols.The curing behavior of epoxy resin/maleic anhydride was studied by FTIR, DSC and NMR. The analysis results indicate that epoxy resin participates in both ring-opening and Diels-Alder reaction, namely double curing reaction. The variation of D-A reaction degree in BPFAEP/MAH system with the length of time was studied by 1H-NMR. Also the reaction degree of D-A reaction in the curing system is 35.75% tested by NMR. DMTA analysis indicates that cured epoxy resin with furan group has higher heat resistance than cured E51 epoxy resin with maleic anhydride as same curing agent.Compared the gel-time length of epoxy resin with furan group and E51 epoxy resin with several kinds of curing agents, epoxy resin with furan group/curing agents system has faster curing reaction rate than E51 epoxy resin/curing agents system. |
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