Coemulsion and electrodeposition properties of mixtures of polyoxypropylene‐modified cationic epoxy resin and nonionic trimethylolpropane–toluene diisocyanate–2‐ethylhexanol crosslinker

Abstract

AbstractThe emulsification and electrodeposition properties of mixtures of polyoxypropylene‐(POP) modified cationic epoxy resin (III) and nonionic trimethylolpropane–toluene diisocyanate–2‐ethylhexanol (TMP–TDI–2EH, V) were investigated and the compositions of their electrodeposited films were obtained by Fourier Transform Infrared (FTIR) quantitative analysis to study the effects of “soft segment” (oxypropylene groups) contained in resin III on the coemulsion and electrophoretic behavior. The results indicate that the deposition yield and throwing power of emulsion of resin III are highly dependent on its average molecular weight (Mw). Resin III with higher Mw has higher deposition yield but lower throwing power. Moreover, the deposition yield of V/III coemulsion also increases with increasing the Mw of III. On the other hand, the throwing power of V/III coemulsion is not related to the Mw of III but is influenced by the amount of soft segments in III. Increasing soft segment content in III increases the throwing power of the coemulsion. Furthermore, at the conditions providing stable coemulsion, the composition of the electrodeposited film is almost equal to the resin composition of the coemulsion. © 1993 John Wiley & Sons, Inc.