Effect of polyether/polyester polyol ratio on properties of waterborne two-component polyurethane coatings

Abstract

In order to obtain waterborne two-component polyurethane (WB 2K-PUR) with good mechanical properties as well as excellent corrosion resistance, a series of hydroxyl-based polyurethane (HO-WPU) were synthesized using isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA), and different proportions of polyether polyol (PTMEG) and polyester polyol (P1012) in this paper. Then WB 2K-PUR coatings were prepared with water-dispersible isocyanates (WDPI) as curing agent. The influence of the proportion of polyester polyols and polyether polyols in soft segments on coatings properties was studied. The characteristics of the coatings were analyzed by Fourier transform infrared spectroscopy (ATR-IR), contact angle, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and atomic force microscopy (AFM). The results showed that the mechanical properties and corrosion resistance of polyester and polyether polyols with appropriate proportion are improved significantly. The mechanism tended to be that with the addition of polyester, more hydrogen bonds were formed between the molecules, which increased the compactness of the coating as a physical crosslinking point. However, the ester groups have a strong affinity to water molecules, so the hydrophilicity of the coating was increased by excessive polyester polyols, and the shielding effect on the corrosion medium was reduced. With the inclusion of 40 % (g/g) P1012 in polyols, the coating has satisfied comprehensive properties.