Study On Synthesis And Modification Of Addition Silicone Rubber With High Transparency And Refractive Index

As a new lighting devices, light-emitting diode （LED）, because of its’ small working current, low energy consumption, no pollution, long life, energy saving, convenience and other significant advantages, have been widely used in backlight, display screen, traffic signal light and so on. With the development of LED lighting technology, there will be high requirements for LED encapsulation technology. Additioned silicone rubber is a new type of LED encapsulation material, which has some advantages with high transparency, high refractive index and aging resistance, while its mechanical properties, heat resistance and thermal conductivity are not good enough for LED encapsulation.Using the vinyl silicone and vinyl silicone oil as based material, hydro-siloxane and hydrogen poly-siloxane as crosslinking agent, A series of addition-cured silicone rubber were prepared. The material matching and vulcanization processing condition were tested. In addition, the performance of Al₂O₃ nanoparticles in silicone rubber was tested and it found that the Al₂O₃ nanoparticles were good for increasing the thermal properties of silicone rubber. MDQ silicone also was used to reinforce silicon rubber. The full thesis included five chapters, which contained:Chapter 1:Literature review. The background and significance of this topic were firstly introduced. The components, vulcanization mechanism, the performance requirements for LED encapsulation material were briefly outlined. The common modification methods along with their research progress were discussed in detail. Finally, the research objective and content were raised.Chapter 2:The influences of the type, structure, consumption of each component on silicone rubber were roundly discussed. The inhibition and antifoaming effects caused by 1,2-divinyltetramethyldisiloxane on curing system were discovered. Through the DSC curve and infrared spectra, the optimum curing temperature and time were established. The silicone rubber for LED encapsulation, of which transmittance was up to 96% and refractive index was up to 1.54, was successfully synthesized by optimizing the curing process.Chapter 3:The influences caused by the change of parameters on the activation index of modified A1₂O₃ nanoparticles were studied in detail. The experimental results show that A1₂O₃ nanoparticles modified by coupling agent AR had compatibility with silicone rubber though SEM. It was found that the silicone rubber could obtain excellent mechanical properties and good thermal conductivity by adjusting the amount of modified A1₂O₃ nanoparticles. Its weight loss rate was 23.9% and thermal conductivity was 0.31 W/（m · k）.Chapter 4:The structure of MDQ silicone samples was characterized and it was identified as methyl phenyl vinyl MDQ silicone resin. The experimental results show that it was possible to obtain silicone rubber with high transparency, high refractive index, good mechanical properties （hardness of 50A, a tensile strength of 1.528MPa, breaking elongation rate of 69.1%）, when the amount of silicone MDQ was up to 25wt%of vinyl base material.Chapter 5:Conclusion.The research achievements in each part were generalized and the main conclusions were summed up.