| Epoxy resin is a kind of macromolecule,which has two or more epoxy groups,employs organic compounds for molecule skeleton such as aliphatic,alicyclic group or aromatic organic compounds,and can form useful thermosetting products by the reaction of epoxy groups.The curing epoxy resin products has excellent physical performance, mechanical properties,bonding power and heat resistance,as a result,it has been widely used as half-conductor and superconductor packaging materials,coatings,adhesives,molding materials,matrix resin of the fiber-reinforced composite materials et al.In this paper,the types and properties of epoxy resin,curing agents,the research development of epoxy resin are reviewed.The purpose is to prepare a new hydantoin type of epoxy resin and study its curing process and the curing coating performance.First of all, 5,5-dimethylhydantoin(DMH-EP) epoxy resin and hydantoin-bisphenol A epoxy resin(DMH-BPA-EP) were prepared and characterized.The factors which may influence on the epoxy value of the two kinds of epoxy resin prepolymer were discussed such as the ratio of raw materials, the concentration of sodium hydroxide,the reaction temperature,the reaction time and so on.Through the experimentation each of their preparation conditions were determined.The study found that 1) The preparation conditions of DMH-EP were as follows:the reaction temperature was 80℃,n(DMH)/n(ECH) was 1∶8,the mass fraction of NaOH solution was 30%and reacted for 3h.The epoxy value(E) of the new prepared DMH-EP was 0.1899 mol/100 g,the average molecular weight(M_n) was 1053 and the intrinsic viscosity(η) was 1.9383 mL/g;2) The preparation conditions of DMH-BPA-EP were as follows:the reaction temperature was 70℃,(n(DMH)+n(BPA))/n(ECH) was 1∶8, n(DMH)/n(BPA) was 7∶3,the mass fraction of NaOH solution was 30% and reacted for 3h.The epoxy value(E) of the new prepared DMH-BPA-EP was 0.2602 mol/100 g,the average molecular meight(M_n) was 769 and the intrinsic viscosity(η) was 1.5454 mL/g.The structures of the synthetic resins were characterized by Fourier transform infrared spectroscopy(FTIR) and Nuclear magnetic resonance spectroscopy(~1H NMR).The results showed that ring-opening addition reaction was occurred between secondary amino group of DMH and ECH,and ultimately yielded DMH-EP with end-functional epoxy groups. Correspondingly,ring-opening addition reaction was also occurred between the hydroxyl of Bisphenol A and ECH,and generated DMH-BPA-EP with end-functional epoxy groups.Secondly,the curing research was carried out by using the above prepared prepolymers with two curing agents 593 and AⅡ,respectively. The effect of amount of curing agent,curing temperature on curing rate of coatings and hardness,and the film hardness,adhesion,gel fraction and chemical medium resistance capability were studied.The results showed that when the amount of curing agent reached 30wt%and the curing temperature was above 120℃,the curing system can receive rapid curing speed relatively.When the curing time was more than 180 min it can get a kind of colorless or light yellow curing film with higher gel fraction(95%),hardness(2H～4H),adhesion(grade 0～1),excellent chemical resistance capability.The curing process and thermal performance of curing systems were investigated using Differential scanning calorimetry-Thermogravimetry(DSC-TG).The results showed that open-loop curing reaction was occurred between the amino and secondary amino groups of 593 curing agent and the epoxy groups,while the exchange reaction was occurred between AⅡcuring agents and the hydroxyl of epoxy resin,and the hydroxyl and epoxy groups occurred ring-opening reaction with the catalyst tertiary amine,accompanied by self-condensation reaction of AⅡcuring agents;the thermal performance of the curing products of DMH-EP was better than the curing products of DMH-BPA-EP.And the curing films were characterized by FTIR.The results showed that the characteristic absorption peak of epoxy groups disappeared,which further confirm the results of DSC-TG. |
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