Preparation And Properties Of Organosilicon Modified Epoxy Resin As Encapsulating Materials For LED

Compared with the traditional lighting equipment, the advantages of Light-emitting diode (LED) are more evident, such as energy conservation, energy-saving,environmental protection friendly, and long-life and other advantages. As LEDpackaging materials, epoxy resin has excellent mechanical properties, such as goodadhesion, sealing and good corrosion resistance, etc. But the main drawback of thismaterial contains strong curing internal stress, low impact strength, poor heatresistance and aging resistance, leading to reduce the life of the LED devices. How tomodify epoxy resin and match the requirements for LED devices attract great attention.In this paper, two kinds of polyhedral oligomeric silsesquioxane(POSS) withdifferent molecular weight, named P-1and P-2, were synthesized. The influencing factorson reaction were determined by using orthogonal experiment method.The results showedthe sequence of influencing factors as follow: the amount of water> the amount ofhydrochloric acid>reaction time>reaction temperature. Furthermore, another kind ofbranched polysiloxane, named K-D, was synthesized. All the chemical structures of thethree polysiloxanes were confirmed by FT-IR and NMR measurements.The mechanical properties, such as impact strength, flexural strength, and heat resistanceproperties testing of bisphenol A type epoxy resins with or without modification agents of P-1,P-2and K-D were carried out. The results show that all the polysiloxanes can improve theimpact strength and flexural strength of the modified epoxy resins, especially for the epoxyresin modified with P-1.When15wt%of P-1was added to epoxy resin (EP1-15), the impactstrength and the flexural strength of the modified epoxy resin reached32KJ/m2and46MPa,increasing by216%and52%, respectively, as compared to the neat epoxy resin. At the sametime, the glass transition temperature of EP1-15reaches the maximum value of123.9°C whilethe pure epoxy resin was113.8°C. The TG data revealed that5%thermal decompositiontemperature, as well as the carbon residue of EP1-15was much higher than that of pure epoxyresin.UV resistance is also better than pure epoxy resin. In addition, all the refractive indexand light transmittance of epoxy resin with or without the three kinds of polysiloxanesexhibited no more different. All the results come to a conclusion that the epoxy resin modifiedby P-1showed the best comprehensive properties among the three kinds polysiloxanes.On the basis of the above studies, P-1was chose to modify alicyclic epoxy resin toexplore the performance before and after modification. The study founded out that the impact strength was increased by140%when25-wt%P-1was added to the alicyclic epoxyresin. However, the glass transition temperature and the initial thermal decompositiontemperature of the modified alicyclic epoxy resins decreased slightly, but the products stillmeet the requirements of LED devices.