Synthesis and characterization of cathodic electrodeposition coatings based on octadecyl-modified cationic waterborne polyurethanes

Aimed at increasing the hydrophobicity of cathodic electrodeposition (CED) coatings based on cationic waterborne polyurethanes (WPUs), a series of cationic WPUs with hydrophobic octadecyl side chains were successfully synthesized by introducing 1-monostearoyl-rac-glycerol as a diol chain extender. ATR-FTIR spectra and SEM images showed the degree of phase separation between soft segments and hard segments of cationic WPUs clearly increased by incorporating octadecyl groups. The water contact angle and water absorption studies showed that the water-resistance property of modified CED coatings was obviously enhanced because of the incorporation of a low surface energy unit and the formation of a more sophisticated surface induced by hydrogen bonds. The International Standardization test of paints and varnishes revealed that the CED films possessed excellent hardness, adhesion, flexibility, and impact resistance. Optical transmittance tests showed that the sample films possessed excellent optical transmittance of about 90%, and meanwhile, the thermostability of the film was promoted.