Effect of Curing Temperature on Morphology and Properties of Polyureas Based on Polyaspartic Esters

In this paper the effect of curing temperature on the morphology and properties of PAE based polyureas were evaluated using FTIR, AFM and electrochemical impedance spectroscopy (EIS). The PAE based polyureas were prepared from synthesized PAE chain extenders and hexamethylene diisocyanate（HDI）trimer/polytetramethylene ether glycol (PTMG) prepolymer. The morphology and properties were investigated through FTIR, EIS and atomic force microscope(AFM). The results indicated that curing temperature has a great influence on morphology and properties of the polyureas. FTIR studies showed that hydrogen-bonded urea carbonyl are increased from 74.3% to 82.1%, and the length of hydrogen bonding were decreased from 0.307 nm to 0.303 nm while curing temperature were increased from 20°C to 80°C. FTIR experimental studies indicated that the degree of hydrogen-bonded –NH groups and urea carbonyl groups increased while curing temperature increased, as a consequence, intermolecular force enhanced. The AFM was applied to study the topography of PAE based polyureas for the first time,and the microphase separation phenomenon of the PAE based polyureas were observed directly through AFM topography studies. AFM studies confirmed that the compatibility of soft and hard segment decreased and microphase separation degree increased while the curing temperature increased. The EIS studies indicated that during 90 days immersion, the resistance of 20°C cured samples changed obviously higher than 80°C cured ones. The results showed that much corrosion medium permeated into the coatings, and the corrosion resistance of 80°C cured PAE based polyureas exhibited a higher EIS features and a better corrosion resistance than the 20°C cured ones. The effect of curing temperature on EIS properties of PAE based polyureas could be confirmed by FTIR and AFM morphology studies.