Improving the Hydrophobicity and Insulation Properties of Epoxy Resins by the Self-Assembly-Induced Coating of Fluorinated Graphene

Moisture and insulation deterioration are important factors that cause the failure of epoxy packaging materials. Thus, improving the long-term stability of epoxy resins in a hot and humid environment is an important prerequisite for electronic components to adapt to complex working conditions and achieve high power densities. In this study, fluorinated graphene doped with hydroxy-terminated poly(dimethylsiloxane) was prepared and self-assembled into a micro/nanostructure on the surface of an epoxy resin, which effectively improved the surface hydrophobicity of the epoxy resin. In addition, the doping with hydroxy-terminated poly(dimethylsiloxane) modified the fluorinated graphene filler, thereby forming an arch bridge energy band structure inside the epoxy resin and thus regulating carrier migration. The water absorption of the epoxy resin decreased from 1.02 to 0.24%, and the surface water contact angle increased from 93.58 to 133.2°. Moreover, the electrical insulation performance of the modified epoxy resin was greatly improved when the surface resistivity and flashover voltage increased by 50.5 and 36.4%, respectively. Therefore, the proposed method realizes a simultaneous improvement in the hydrophobicity and insulation of epoxy resins.

Strategies for the synthesis of fluorinated polyesters

In this work we synthetized three fluorinated polyesters from dimethyl tetrafluorosuccinate (DMTFS), dimethyl hexafluoroglutarate (DMHFG), and dimethyl octafluoroadipate (DMOFA) and ethylene glycol. The influence of parameters like monomer's size, temperature, vacuum, ultrasound and catalyst, on the polyesters synthesis was evaluated. The conversion rates were assessed considering ¹H NMR data and the results disclose the role of ultrasound (US) as crucial to attain high reaction conversion rates (≈20% of increase relatively to the reactions performed in absence of US). The effect of US was more relevant for the higher molecular weight monomers (DMHFG and DMOFA). The use of Candida antarctica lipase (immobilized CALB) marginally favors the synthesis reactions when fixing the other conditions. The size of the starting monomers influenced greatly the reaction conversion rates, as shorter monomers gave rise to high amount of product recovering. All the produced polyesters were isolated and fully characterized by NMR (¹H and ¹⁹F), FTIR, TGA and MALDI-TOF.

In this work we synthetized three fluorinated polyesters from dimethyl tetrafluorosuccinate (DMTFS), dimethyl hexafluoroglutarate (DMHFG), and dimethyl octafluoroadipate (DMOFA) and ethylene glycol.