Study On Ultraviolet Resistance Of Modified Epoxy Resin With Nano ZnO

With the development of LED industry, higher requirements have been addressed to encapsulation materials-epoxy resins. Making epoxy resins UV resistant, slowing the aging speed, prolonging LED's life time are very important topics.Epoxy resins used for LED age quickly in the UV light, and the conventional organic UV absorbers have their own shortcomings. Inorganic UV-shielding materials have these advantages: clarity, heat stability and chemical stability, so, they have a broad future. Nano-ZnO shows a good property of visible light-transparency and UV-shielding, it can be used to modify epoxy resins.In this paper, the synthesis of nano-ZnO was studied. First, Zinc oxalate is prepared by the zinc nitrate and oxalic acid through the following procedures of precipitation, washing, separation, drying and then zinc oxalate is calcined to prepare ZnO. Based on DTA-TGA technique, we find zinc oxalate decomposes at the temperature of 500℃. Several factors that influence the particle size are studied. The optimal conditions for producing high performance ZnO are as follows: the microwave power is 700 w, the microwave radiation time is 30 min, the calcination temperature is 500℃and the calcination time is 1 h. In the end, through XRD, the product is proved to be the hexahedral crystal with high purity.The nano-ZnO particles are pre-treated before introduced into epoxy resins. Since the nano-ZnO particles have a large specific surface and then high surface energy, it is easy for nano-ZnO aggregating together if mixed directly into resins. So, the silane coupling agent KH550 is used to make nano-ZnO particles have the affinity to organic materials and then dispersed fully in epoxy resins.Epoxy resin/ZnO nanocomposites are prepared through the solution-mixing method. The structures and properties of the composite are analyzed and discussed through the means of the SEM, IR, DTA. Influences of the amount of nano-ZnO particles filled in epoxy resins on the materials's property of visible light-transparency and UV-shielding are studied through the accelerated aging experiments. It is found that when the weight amount of the particles is 0.06%, the materials have the best property of visible light-transparency and UV-shielding. At the same time, it is also found that such little amount of particles have hardly effect on the mechanical and thermal properties of epoxy resins.