Effect of montmorillonite modification on rheological properties
of organic coating systems containing MMT
Polimery 2008, No 7/8, 551
Rheological properties of coating systems and possibility of their modifications especially by montmorillonite were characterized (Table 1) on the basis of literature data. In the own research either hydrophilic or hydrophobic modification of purified montmorillonite (MMT-S) was carried out. Hydrophylic modification with sodium salts of carboxymethyl cellulose (CMC) of various substitution degree was done while hydrophobic one carried out with amines of long hydrocarbon chain [1-hexadecylamine (A-1), ethoxylated amines containing radicals of coconut acid (A-2) or thallic one (A-3) (see Table 2)]. Spectroscopic methods, namely FT-IR (Fig. 4, 5, 8 and 9), X-ray diffraction (XRD, Fig. 1, 2 and 12) and wide-angle X-ray scattering (WAXS, Fig. 13), were used for characterization of an effectiveness of MMT-S modification. In case of hydrophylic modification the largest changes were observed for the samples modified with CMC characterized with substitution degree equal 0.9 and with 50 wt. % of modifier. For hydrophobic modification with amines the part of modifier at least 1.0 CEC (CEC is a measure of cation exchange capacity) was necessary. Mixed modifier A(1+2) appeared to be the best one. Properly modified montmorillonites show improved swelling ability in aqueous and organic media (Fig. 10). It was found, on the basis of viscosity measurements and rheometric investigations, that montmorillonites could govern the rheological properties of waterborne paints and act as thickeners for solventborne paints.
Key words: montmorillonite, modification, waterborne paints, solventborne paints, rheological properties, governor
H. Kuczyńska, E. Kamińska-Tarnawska, P. Majkrzak
Effect of montmorillonite modification on rheological properties of organic coating systems containing MMT