Comparison of phase structures and surface free energy values for the coatings synthesised from linear polyurethanes and from waterborne polyurethane cationomers

WAXS, DSC and AFM methods were employed to compare phase structures of the coatings obtained from waterborne polyurethane cationomers which had been synthesised in the reaction of some diisocyanates (MDI, IPDI, TDI and HDI) with polyoxyethylene glycols (M = 600 and 2,000) and butane1,4-diol or N-methyl- or N-butyldiethanolamine and 2,2,3,3-tetrafluoro-1,4-butanediol. The structures were also analysed of the coatings derived from linear polyurethanes which had been synthesised on the basis of similar raw materials. Better rigidity was found for generally amorphous cationomer coats. Changes were discussed in the surface free energy (SFE) values and in their components, as calculated independently with the use of the van Oss–Good and Owens–Wendt methods. Polyurethane coats turned out more hydrophobic as compared to cationomer ones. In both coat types, fluorine incorporated into cationomers contributed to lower SFE values: from 50 down to about 30 mJ/m2

A fluorescence approach to investigate repartitioning of coalescing agents in acrylic polymer emulsions

Repartitioning of co-solvents between particles of latex emulsions was investigated by means of a fluorescence method based on the detection of the amount of co-solvent via the solvatochromic shift of the emission maximum of a fluorescent probe, copolymerized at a low concentration. Complete repartitioning of co-solvents between particles of latex materials with a low Tg (ca. 25 °C) occurred within minutes. For a hydrophilic latex with a Tg of 68 °C, equilibration was achieved within an hour. Repartitioning was faster for more hydrophobic co-solvents. For a hydrophobic latex of similar Tg, co-solvent repartitioning took place on the same time scale, but complete equilibration was not reached. Possibly, there is an additional slow component in the repartitioning, or the prolonged presence of co-solvent causes a structural change in the latex particles that affects the outcome of the experiment