| Résumé : |
A matrix of coating variables, nonassociative versus associative thickeners, different latex median particle sizes, individual surfactants and colorants [carbon black (CB), red, and yellow pigments], was examined for their influence on variances in coatings rheology and color development. Within the different coating groups, the variable of interest in this study was the surfactant added to the colorant formulation. In all three colorant formulations, sodium dodecyl sulfate (an anionic surfactant) provided poorer color development (CD) than in applied formulations containing an equivalent nonylphenol oxyethylene (EO) surfactant. In CB formulations, nonionic surfactants with higher EO content provide improved color development at low (2 mM) concentrations, but near equality in CD is achieved with low EO surfactants at higher concentrations, in contrast to CB formulations, red and yellow colorants exhibit good color development with high EO content nonionic surfactants only at low nonionic surfactants concentrations. This variance appears to be related to the interactions of surfactants with inorganic pigments (talc and laponite) in the colorant formulation. The coating's rheology is related to latex, thickeners, and surfactant components of the paint, as has been noted in previous studies, but not to the nature of the color pigment. The viscosity of the hydroxyethyl cellulose (nonassociative type) and HEUR (associative type) thickened paint decreased with colorant addition due to dilution effects. There were no unusual deviations with the NP(EO)x surfactants, except when a large hydrophobe nonionic surfactant [e.g., C18H37(EO)100] is added. In HEC thickened coatings, the viscosity decreases when C18H37-(EO)100 is in the colorant due to that surfactant inhibiting depletion flocculation. In the C18H37(EO)100 coatings containing the HEUR thickener, significant increases in viscosity were observed, above the dilution values observed with the colorant addition. This is related to the viscosity maximum in the low concentration of HEUR with the C18H37(EO)100 surfactant. Color development is independent of the viscosity profile of the coating. |
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Waterborne latex coatings of color : II. Surfactant influences on color development and viscosity in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 2, N° 8 (10/2005)
