Study On TTT-η Diagram And Curing Molding Of High-refractive Polyurethane Optical Resin

With the development of economy,the optical resin lens is gradually replacing the optical glass lens.High-refractive resin,which can make the optical resin lens thinner and lighter,has become the favor of many researchers.At present,the development of high-refractive optical resin lenses represented by polyurethane has become a hotspot in the market.However,the development of China’s lens industry is severely restricted due to the lack of raw materials and immature curing process,and the market is almost monopolized by foreign countries.In this dissertation,two reaction systems,m-xylylene diisocyanate（XDI）/2,3-dithio（2-mercapto）-1-propanethiol（BES）and the cyclohexyl dimethylene diisocyanate（H₆XDI）/2,3-dithio（2-mercapto）-1-propanethiol（BES）were selected.The temperature-time-transition-viscosity（TTT-η）curve of two kinds of high refractive optical polyurethane resins was established by studying the curing kinetics,gel transition and chemorheology of the two systems.The curing procedures of XDI/BES and H₆XDI/BES systems were designed by the TTT-ηdiagram and curing dynamics,and the feasibility of the two curing procedures in the processing of optical polyurethane lens substrate were investigated.（1）Based on the phenomenological model,the relationships among curing degree,temperature and time in XDI/BES and H₆XDI/BES systems were obtained by combining the autocatalytic reaction model and n-order reaction model with dynamic DSC scanning test and constant temperature DSC scanning test.By combining the relationship between curing degree,temperature and time with Dibenedetto equation,the relationship among the vitrification temperature,temperature and time in the two systems was obtained.The gelation time of the two systems at different temperatures was measured by rotary rheometer,and the gelation model curves of the two systems were obtained.The temperature-time-transition（TTT）curves of XDI/BES and H₆XDI/BES systems were further obtained,which demonstrated the relationship between the gelation and vitrification of the resin under different curing processes and pointed out the curing degree at different（T,t）points.（2）The viscosity of the two systems during curing were monitored by rotary rheometer,Viscosity model curves of the two systems were established by double Arrhenius equation and plotted on the corresponding TTT diagram to obtain the TTT-ηdiagram of the two systems.The diagram provides more reference for the selection of process parameters,and comprehensive information about the resin during curing,thus becoming a platform for process optimization and design.（3）The TTT-ηdiagram and the results of curing kinetics were combined to design the curing procedures of the two systems.The XDI/BES system curing procedure was determined as:289.5 K～303 K 2 h,303 K～320 K 1.5 h,320 K 1h,320 K～393 k 4 h,393 k 2.5 h,393 k～346.5 k 2 h.The H₆XDI/BES system curing procedure was determined as:295.8 K～323 K 1 h,323 K～352 K1 h,352 K 3.5 h,352 K～393 K 2.5 h,393 K 6.5 h,393 K～350.9 K 2 h.The above curing procedures were applied to the curing and forming of the optical polyurethane lens,and the properties of the two kinds of lens substrates were tested and characterized by the transmittance,the refractive index,the abbe number,the optical profile,thermogravimetic,scanning electron microscope and impact resistance experiments.The refractive indexes of the XDI/BES system and the H₆XDI/BES system lens substrates are 1.665 and 1.617,and the light transmittances are 92%and 94%,respectively.The results showed that the optical properties of two substrates both reach the national standards and the eyewear industry standards,which proves that the TTT-ηdiagram obtained in this paper has guiding significance for the curing of optical polyurethane.