| Optical epoxy resin has been widly used in optical device packaging materials,optical lenses,anti-reflection layers,optical waveguide materials,exquisite crafts and other fields due to its excellent wear resistance,easy processing,low cost and excellent optical performance.However,the optical epoxy resin is extremely easy to burn.Once it is ignited,the fire spreads rapidly and releases a lot of heat and toxic and harmful smoke,so it needs to be flame-retardant modification.Unfortunately,the optical properties of epoxy resins are significantly reduced after flame retardant modification,which greatly limits the scope of application of optical epoxy resins.Therefore,how to achieve a balance between the flame retardant performance and optical performance of the optical epoxy resin so as to be able to meet the use requirements in related fields has attracted immense interest.In this paper,a phenol epoxy resin（PF）was prepared from phenol,formaldehyde and epichlorohydrin.The transparent epoxy cured product PTDP-PF was obtained by crosslinking and curing with the intrinsic and transparent flame retardant curing agent PTDP containing phosphorus and sulfur prepared in the early stage of the laboratory.The chemical structure of phenolic epoxy resin was characterized by 1H-NMR and FTIR,and the optical properties and flame retardant properties of epoxy cured product PTDP-PF were tested.The optical performance test results show that:the transmittance of 32PTDP-PF can reach 85.9%in the visible light range,refractive index of 32PTDP-PF can reach 1.594.Meanwhile,the limit oxygen index value（LOI）value of 32PTDP-PF can be increased from 20%to 27%,and the vertical burning test（UL-94）reachs V-0 level;and the results of the cone calorimetry show that the THR value of PTDP-PF is reduced by 44.72%and the p HRR value decreased by 24.6%,compared to PEI-PF.The above results show that PTDP-PF not only has excellent flame retardant properties,but also has excellent transparent refractive properties.In order to further improve the flame-retardant efficiency and optical properties of epoxy resin,a cured epoxy resin PTDP-EA by crosslinking and curing a sulfur-containing epoxy resin（EA）and PTDP is prepared,and then the chemical structure of sulfur-containing epoxy resin is characterized by 1H-NMR,13C-NMR and FTIR.Subsequently,the flame retardancy of PTDP-EA performance and optical performance are discussed.The flame retardant and optical performance results of PTDP-EA show that the flame retardant performance of PTDP-EA is significantly improved comparing with PEI-EA.When the addition of PTDP is 30wt%,the LOI of PTDP-EA can be increased from 19%to 25.5%,and the UL-94 can be increased from no rating to V-0 level;the results of the cone calorimeter test show that the p HRR value of PTDP-EA is reduced by 63.0%,and the THR value is reduced by 29.7%;optical performance test results show that PTDP-EA show that the transmittance can reach 85.6%in the visible range and the refractive index of PTDP-EA can reach 1.619.Therefore,the above results show that PTDP-EA not only display excellent flame retardant properties,but also exhibit excellent transparent refractive properties. |
