| Epoxy resin is an important thermosetting resin.The cured epoxy resin has good electrical properties,bonding properties and mechanical properties.Therefore,epoxy resin is widely used in the fields of machining,aerospace and many other fields.However,the epoxy resin has a high crosslink density after curing,resulting in a large internal stress,low toughness,and poor impact resistance,which limits its practical application.Therefore,it is important to modify the epoxy resin.In this paper,epoxy resin is modified by epoxy-terminated silicone.The epoxy-terminated silicone can be directly blended with the epoxy resin without complicated process.During the curing process,the epoxy-terminated silicone can be crosslinked with the epoxy resin into the coating system by epoxy ring opening.This modification reduces process complexity and effectively introduces the silicone modifier into the coating system by chemical reaction.In this paper,the bisphenol A epoxy resin was modified by self-made epoxy phenylmethylpolysiloxane(EPMS).We have successfully prepared a series of epoxy-silicone composite coatings with smooth surface,good hydrophobicity,strong adhesion,high temperature resistance and corrosion resistance.According to the results,we found that the performance of the coating was improved as the increasement of modifier content.Coating with the best quality contained 30wt%modifier.Compared to the unmodified coating,the initial decomposition temperature was increased by 23.68℃.Besides,the electrochemical impedance modulus increased about 20 times,and the static contact angles raised from 86.2° to 108.9°against water.Bisphenol A epoxy resin got excellent adhesion after modification,meanwhile the coating integrity increased to 100%.The epoxy value of self-made epoxy phenyl methyl polysiloxane is too low and the amount of modifier needed in curing process is quite large.However,adding a large number of modifiers will lead to phase separation of the coating,poor curing effect,and great increasement of economic cost,which is not suitable for industrial production and application.Therefore,we choose commercially available glycidyl ether oxypropyl dimethyl polyphenylsiloxane(PPES)with epoxy value of 0.15 mol/100g as modifier.By adding PPES to bisphenol A epoxy resin,we have successfully prepared a series of epoxy resin-silicone composite coatings with smooth surface morphology,high tensile strength,good impact strength,strong waterproof penetration ability,high adhesion and wet adhesion,high temperature resistance and corrosion resistance.When the proportion of PPES added is 15%,the initial decomposition temperature,Tmax and glass transition temperature of the composite coatings were increased by 30℃,58℃ and 20.14℃,respectively.Besides,the solid residue was increased by 7.53%at 800℃.The tensile strength and elongation at break of PPES-15 increased by 26.21%and 86.93%,respectively.The modified coatings were evaluated by FESEM,and the results showed that the addition of PPES not only improved the surface morphology,but also improved the corrosion resistance of the coatings.After aging and penetration of PPES-15 coating in 3.5wt%NaCl solution,the coating integrity was improved to 93.6%.Through the contact angle test and the water absorption test,it was found that the waterproof permeability of the coating increased greatly when the addition of PPES was controlled between 15%and 20%.EIS study found that the Rct of PPES-15 coating increased by about 26 times,while the double-layer capacitance of the system decreased by about 29.5 times.The impedance modulus of PPES-15 coating was more than 60 times higher than that of the initial coating.These data showed that the corrosion resistance of epoxy resin coatings has been greatly improved by the modification of PPES. |
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