Elastic 'breather' paints, permeable to moisture vapor, have been formulated with low Tg latex polymers, utilizing microgels produced via an emulsion polymerization process. These microgels were designed to have a hydrophilic sheath surrounding a crosslinked acrylic core. The moisture vapor transmission rates of the films were measured and showed a 10-fold increase when the microgel was included in the formulation, with no sacrifice of either the water-resistance property or the carbon dioxide gas barrier performance. Low molecular weight surfactants were tried as an alternative to the microgels, but failed to attain the improved permeation performance. TEM observation demonstrates that the microgels segregate within the interfacial space between the coalescing latex particles, forming a fine percolating texture. The mechanism for moisture vapor permeation through the films which contain microgels is discussed in more detail. © 1992.
Yagi, T., Saito, K., & Ishikura, S. (1992). Coatings containing microgels. II. Moisture vapor permeable coatings. Progress in Organic Coatings, 21(1), 25–35. https://doi.org/10.1016/0033-0655(92)80009-L