| As a kind of thermosetting resin with excellent overall performance,epoxy resins are widely used in laminates,adhesives,electronic packaging materials,coatings and other fields for its good corrosion resistance,adhesive properties,electrical properties and dimensional stability.With the development of related application industry technologies,the performance requirements for epoxy resins are also increasing.The disadvantages of poor toughness and poor heat resistance of conventional epoxy resins make it increasingly difficult to meet application requirements.Therefore,to modify and prepare high-performance epoxy resin with better mechanical properties and heat resistance has important research significance and practical value.Based on this,bisphenol A type epoxy resin which is the most commonly used was chosen as the matrix in this paper.It was modified with several kinds of organic silicon,and two kinds of organic and inorganic nano fillers were selected for further modification.The mechanical properties,thermal properties,aging resistance and micro-morphology of the modified epoxy resin were systematically studied.Firstly,two new types of silicon modified epoxy resins were successfully synthesized by using Vinylmethyldimethoxysilane?VMDMS?and Dihydroxydiphenylsilane?DHDPS?as modifiers.The effect of silicone modification on the properties of the epoxy resins was systematically studied.The results showed that VMDMS modification can significantly improve the impact and tensile properties of epoxy resins.Impact strength and bending strength increased by 51.2%and 31.9%,respectively.In addition,the glass transition temperature of the material was increased by 16.2°C,and the heat resistance was also improved.T10%,T50%,and Tmax were improved by 2.8°C,21.6°C,and 2.4°C,respectively,compared with those of the pure epoxy resin before modification.The residual mass at 800°C also increased from 13.4%to 21.9%.At the same time,the UV aging resistance of epoxy resin was also significantly improved.On the basis of adding DHDPS for modification,the mechanical properties of the modified epoxy resin were significantly improved,but the addition of DHDPS reduced the heat resistance of the epoxy resin,and the glass transition temperature and initial decomposition temperature of the material showed a small decline.In addition,the modification of both VMDMS and DHDPS increased the water absorption of the epoxy resin.Nano-silica was surface modified by several silane coupling agents,and the treated nano-silica was filled into silicon-epoxy resins for modification.The effect of different dosage and temperature on the modification effect was studied.The results showed that the dispersibility of nano-silica modified by the silane coupling agent was significantly improved;while modified by 3 parts of modified silica at 150°C,the mechanical properties,heat resistance,ultraviolet resistance of the modified epoxy resin have been improved to some extent.At the same time,the addition of nano-silica greatly reduced the water absorption of the epoxy resin.The nanocrystalline cellulose?CNC?was extracted from microcrystalline cellulose by sulfuric acid hydrolysis method,and what's more,a new type of nanocellulose hybrids was prepared on the basis of the method of in situ hydrolysis and condensation of ethyl orthosilicate on the surface of nanocellulose to produce nano-silica.The nanocellulose and its hybrids were then characterized and used to modify the silicone-epoxy resin.The results showed that the prepared cellulose with I-type structure had a crystallinity of 70.7%and had poor heat resistance.After silica hybridization,the thermal stability of cellulose was significantly improved.In addition,the addition of nanocellulosic hybrids can significantly increase the tensile and flexural properties of epoxy resins. |
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