The impact of rheological modifiers on water-borne coatings

Rheological behavior of aqueous organosilicone resin emulsion stabilized by colloidal nanosilica particles

“…Organosilicone resin with Si-O backbone chains capped with CH 2 =CH-(CH 3 O) 2 Si-endgroup (M w , 6.0 × 10 4 ; viscosity, 31 Pa s at 25 • C) was supplied from Henkle Company (Germany). Three kinds of nanosilica sols (10, 20, and 100 nm, pH 9-10) were the products of Eka Chemicals (Sweden).…”

“…Moreover, the G value decreased more rapidly with the increase in the strain amplitude than G , and was even smaller than G at high strain. This behavior is the characteristic of a flocculated gel-like substance, and larger deformation leads to a partial breakage of the flocculated structure, indicating these systems were consisted of very high interparticulate interactions and behaved strongly elastic [2,20]. The smaller the incorporated colloidal silica particles were, the higher the G of the emulsions was and the longer the linear region where G value was independent of the strain was, resulting stronger interparticulate interaction and higher elasticity.…”

“…The possible stable mechanism could be explained as follows: Since organosilicone macromolecular chains are terminated by CH 2 =CH-(CH 3 O) 2 Si-groups, these groups could react with the silanol groups on the surfaces of colloidal silica particles, or these endgroups were first hydrolyzed to cause silanol groups during emulsification process, then these silanol groups of macromolecules also interacted with the silanol groups on the surfaces of colloidal silica particles via chemical or physical force. As a result, under high shear stirring, the emulsified polymer droplets adsorbed not only emulsifiers but also silica particles on their surfaces.…”

“…For example, emulsion polymerization is empolyed to prepare O/W (oil-in-water) latexes, or emulsification technique of polymers in aqueous phase is used for O/W emulsions. Generally, the emulsification of polymers could be performed via following two ways: One is to introduce some base or acid groups into macromolecular chains first during synthesis process, these groups are then neutralized using acid or base compounds, respectively, followed by high shear dispersing [1,2]. Another is to directly post-emulsify polymers (especially oligomers) in aqueous media under high speed shearing with the aid of emulsifiers [3], which form a protection layer on the surfaces of the dispersing phase by steric hindrance, electrostatic repulsion to stabilize the emulsion.…”

Calorimetric study on interaction of water-soluble copolymers with ionic surfactant

“…The release of VOC during the coating process causes an increase in hazardous chemicals in the environment. Researchers in paint industries have been investing a great deal of effort in the development of the so-called waterborne paints to avoid the VOC-containing paints for environmental concerns [1,2].…”