The Preparation Of Schiff-base Metal Complexes And The Study On The Cured Epoxy Resins

Schiff base metal complex is a kind of promising latent curing agent for epoxy resins. The cured products always have excellent mechanical properties and heat resistance.In this paper, a series of Schiff base metal complexes were synthesized and then used as curing agent for epoxy resin. Their effect on the mechanical properties and heat resistance for cured commercial epoxy resin was investigated, mainly including:(1) Eight kinds of Schiff base metal complexes have been synthesized by the reaction between aliphatic amine, metal acetate, salicylaldehyde and its derivatives. The synthetic technology was optimized, and the products were characterized by FT-IR,1H-NMR, elemental analysis, and single crystal X-ray diffraction. The results show that the coordination geometries of ZnVan2trien, ZnSal2trien and NiSal2trien are all distorted octahedron structure. The strength of the central ion-ligand coordination bond was determined by the central metal ion, aliphatic amine ligand and different substituents in the aromatic ring.(2) The TG/DTG curves of epoxy resin cured by Ni(Ⅱ), Zn(Ⅱ)-Schiff base complexes and the reference were investigated, respectivelly. Classical thermal stability parameters of these systems were studied in detail, based on the initial decomposition temperature (IDT, Td), temperature of 50 percent of mass loss (T50), temperature of maximum rate of mass loss (Tmax) and char yield at 600℃(Yc) calculated from the TG curves. The thermal stability of epoxy resin cured by Ni(Ⅱ), Zn(II)-Schiff base complexes was determined by heating the samples in an air oven. Upon heating at 250℃for 48 h, both the weight loss of Ni-and Zn-containing epoxy polymers was less than 4.0%, which is comparable to the known DDM/E-44 system, and much better than dien/E-44 and trien/E-44 system even after high temperature treatment.(3) The thermal stability of metal-containing polymers was determined using isothermal TGA. The tensile shear strength of the epoxy system was measured at room temperature,50℃,100℃,150℃and 200℃, respectivelly. The results show that Ni-and Zn-containing epoxy polymers have good mechanical properties when used below 100℃. The tensile shear strength is 16 MPa at 150℃and 8-10 MPa at 200℃.(4) The weight loss of metal-containing epoxy system was determined using isothermal TGA at different heating rates. Thermal degradation kinetic parameters of these systems were evaluated by Flynn-Wall-Ozawa and Coats-Redfern integral method, respectively. The kinetic parameters have been used to determine the thermal decomposition mechanism and estimate the lifetime of the systems at different temperature. The results are similar to the measured data. Ni-containing epoxy system has better heat resistance than Zn-containing epoxy system. The heat resistance of the epoxy cured by the trien complexes is better than that of the dien complexes. Additionally, substituents on the aromatic ring can also improve the.