Electrochemical Impedance Spectroscopy Analysis of Waterbrone Polyurethane Crossinking And Modification

• Main Authors: Cheng-Wei Su, 蘇政瑋
• Other Authors: Horng-Jer Tai
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/04796440803961257580

碩士 === 義守大學 === 生物技術與化學工程研究所 === 101 === In this thesis, we study waterborne polyurethane (WPU) formulations which are to be applied as an environmentally friendly anticorrosion coating for Al-Zn alloy coated steel sheets. The additives such as hexamethoxymethyl melamine (HMMM) crosslinking agent, trimethoxysilyl propyl diethylenetriamine coupling agent and nano SiO2 particles were evaluated to see their effects on properties of WPU-based coatings. For the WPU/HMMM system, with increasing HMMM concentration up to 10 phr, gel content, mechanical properties, glass transition temperature, water contact angle, substrate adhesion and copper sulfate permeation time increased while water absorption decreased. Electrochemical tests showed WPU formulations with a higher HMMM content had lower corrosion currents and higher corrosion voltages, indicating better anticorrosion performances. By using electrochemical impedance spectroscopy (EIS) coupling with equivalent circuit modeling, we were able to properly assess the anticorrosion performance of WPU/HMMM coatings. Finally, salt spray tests also confirmed our assessment about the performance of these coatings. The addition of the silane coupling agent and the nano SiO2 particles also promoted anticorrosion performance of the coatings. It was attributed to the increase in hydrophobicity of the coatings with the introducing of inorganic SiO2 and the higher adhesion between polymer and SiO2 and metal substrate when the silane coupling agent was added. It was also found that EIS could be a useful tool for the assessment of anticorrosion performance of a coating.