Preparation And Properties Of High UV Transmittance Fiber Coatings

Fiber Bragg Grating(FBG)is the most widely used electronic device in the field of optical fiber sensors.The fabrication process is through phase mask method,using 248 nm KrF molecular device as the light source to write the finished fiber.The prepared fiber coating has a low transmittance of 248 nm ultraviolet light,which leads to the needs to peal off the surface coating when writing the fiber,and re-coating after the writing is completed.This process is easy to causes a certain degree of damage to the optical fiber,and the cost is high and the efficiency is low.Based on the work done by the former workers,combined with the theory of ultraviolet light absorption,through the selection of raw materials and the design and optimization of the synthesis process,polysiloxane polyurethane and large molecular weight hydroxy acrylate were synthesized,respectively.The two are mixed and used to prepare FBG coating with high ultraviolet transmittance and good comprehensive performance.Polysiloxane polyurethane was synthesized by selecting different isocyanate curing agents and different molecular weights of hydroxy silicone oil.The effects of reaction temperature and catalyst dosage on the reaction time of prepolymer were investigated.The effect of curing agent type on 248 nm light transmittance was investigated.The influence of the molecular weight of the hydroxy silicone oil on the light transmittance and curing time of 248 nm,and the thermal stability of the coating film.The best process is as follows: the commercial GI curing agent and medium molecular weight hydroxy silicone oil are used as raw materials,the catalyst dosage is 0.05%,the reaction temperature is 70 °C,the reaction time is 2.5 h,and the prepared film has a light transmittance of 248 nm of 93%;5% decomposition rate is 280 °C,with faster curing rate(260 °C,20 s)and flexibility.Further,hydroxyethyl acrylate and butyl acrylate as raw materials,a dodecanol as is a molecular weight modifier,and AIBN as an initiator,were used prepared a large molecular weight hydroxy acrylate by radical polymerization.The effect of the amount of dodecanethiol and AIBN on the room temperature viscosity of the resin was discussed.The optimal synthesis process was obtained: the amount of dodecanol was 0.03%,the amount of AIBN was 3%,the reaction temperature of the first step was 100 °C,and the reaction time was 30 min,the second reaction temperature is 75 °C,the reaction time is 3 h,the prepared resin has a viscosity of 4000 mPa·s at room temperature;the resin and GI curing agent cured film 248 nm light transmittance is 70%;5% decomposition rate is 300 °C,After the test coating,the coating with the resin as a basic component has a good overall performance.The highly permeable acrylic polyurethane coating was prepared by modifying the polysiloxane polyurethane with hydroxy acrylate.The UV properties of the coating film were investigated by UV-Visible spectrophotometer.The microstructure of the coating film was observed by SEM.The chemical structure of the coating film was characterized by Fourier transform infrared spectrometer.The thermal weight loss analyzer was used.The heat resistance of the coating film was examined.The results show that the prepared resin has a light transmittance of ?87% at 248 nm and good heat resistance(5% weight loss rate corresponds to 325 °C).The surface of the coating film is smooth and has good adhesion(level 0),hardness(4H)and flexibility(1mm).When the high-transmission ultraviolet light coating prepared by using the resin as a basic component is coated with a special optical fiber for grating,the vehicle speed can reach 3 m/s,which is completely matched with the existing equipment and process.In the preparation of grating,the performance is not significantly different from the products prepared by the traditional method,and has good popularization and application value.