| Epoxy resin is widely used in composite materials,adhesives and coatings due to its low shrinkage,good mechanical properties,chemical stability and dielectric properties.However,the cured epoxy resin is brittle,poor in toughness,and easy to crack,which is difficult to meet the requirements of more fields.Therefore,modifying epoxy resin to improve its performance is the key and hot spot of epoxy resin research.In this paper,bisphenol A epoxy resin E-51 is used as the matrix to carry out research on synergistic modification of nano-silica and polyethersulfone.The optimal ratio of dicyandiamide curing agent and organic urea accelerator was studied through non-isothermal DSC experiment,the optimal dosage of curing agent and accelerator was 7 and 1 parts.The optimal curing process was determined to be90?/3h+110?/1h+130?/1h by extrapolation method combined with gel time.The surface modification of nano-silica was carried out by silane coupling agent KH-570.It was proved by infrared spectrum that-CH3 or-CH2 and-NH were grafted onto the surface of nano-silica.The effects of the dosage and dispersion of nano silica on the properties of epoxy resin were studied.The results show that when the amount of modified nano-silica is 3 parts,the comprehensive performance of the cast is the best.The tensile strength and flexural strength were 25.63MPa and 84.1MPa,respectively,and the glass transition temperature was 142.33°C,which was 11.16°C higher than that of pure epoxy resin.The solubility of polyether sulfone in epoxy resin was studied.The results showed that polyether sulfone was compatible with epoxy resin when heated at 120?for 30min.When the dosage of modified nano-silica and polyethersulfone is 3 parts and 10 parts,the casting body has the best comprehensive performance.The tensile strength and bending strength of epoxy resin are 28.39MPa and 117.5MPa,and the glass transition temperature is 129.94?,which is only 1.23?lower than that of pure epoxy resin.Based on the non-isothermal DSC experiment,the curing kinetics of three epoxy resin systems were studied by n-order kinetic model and self-catalytic model.The results show that self-catalytic model can accurately predict the curing reaction process of the system. |
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