Effect of silane as surface modifier and coupling agent on rheological and protective performance of epoxy/nano-glassflake coating systems

Abstract

Epoxy resin nanocomposites suspended with nano-glassflakes (NGFs) are studied in the present work. A bi-functional silane, i.e., epoxy propoxy propyl tri-methoxy silane, was used as coupling agent and NGFs’ surface modifier. Fourier transformed infrared spectroscopy and thermogravimetry techniques confirmed the successful surface treatment of the NGFs. Rheological studies of the polymer composites were carried out by measuring complex viscosity and storage and loss modulus values. The rheological results revealed that the presence of silane either as coupling agent or as surface modifier could decrease the nanocomposite viscosity. It is indicated that reduced filler–filler interaction resulted in better dispersion of NGFs. It can be due to soft layer formation on nano-glassflakes by silane groups which prevents the agglomeration of NGFs and subsequently improves their dispersion quality. Storage and loss modulus investigations showed that an inter-connected network structure in the solution might be formed in the presence of silane, probably due to the interaction between the NGFs and the polymer resin phase. Electrochemical impedance spectroscopies were carried out to study the protective performance of epoxy/nano-glassflakes coatings. Although the electrochemical impedance results revealed that the incorporation of silane as coupling agent and surface modifier in the epoxy/NGF coating systems applied on carbon steel substrates could improve the protective performance, the superiority of the epoxy coating formulated with 0.5 wt% of modified NGF was obviously visible during immersion period.