Synthesis and properties of transparent cycloaliphatic epoxy-silicone resins for opto-electronic devices packaging

Cycloaliphatic epoxy-silicone resins were successfully synthesized through a two-step reaction route: (i) hydrosilylation of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) and 1,2-epoxy-4-vinyl-cyclohexane (VCMX), (ii) blocking of unreacted Si-H in (i) with n-butanol. The molecular structures of the cycloaliphatic epoxy-silicone resins were characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (H-1 NMR and Si-29 NMR). High grafting efficiencies of epoxy groups were confirmed by H-1 NMR combined with weighting results, indicating over 90 mol% of cycloaliphatic epoxy were grafted on the silicone resins. Subsequently, Si-H groups from TMCTS were almost totally consumed after the blocking reactions. In comparison with commercial available cycloaliphatic epoxy resin 3,4-epoxycyclohexylmethy1-3,4-epoxycyclohexanecarboxylate (ERL-4221) cured by MHHPA, the cured cycloaliphatic epoxy-silicone resins exhibited better thermal stability, lower water absorption and higher UV/thermal resistance. Moreover, the characteristics of transmittance (>90%, 800 nm), 5 wt.% mass loss temperature (>330 degrees C) and no yellowing during thermal aging at 120 degrees C or UV aging for 288 h of the cured cycloaliphatic epoxy-silicone resins, made them possible for power light-emitting diode (LED) encapsulants, or other packaging materials, like optical lenses, and electronic sealings. (c) 2012 Elsevier B.V. All rights reserved.