Spray applications: Part IV. Compositional influences of HEUR thickeners on the spray and velocity profiles of waterborne latex coatings

Abstract

In this study, the focus is on the spray behavior of latex coatings thickened with structurally different surfactant-modified, water-soluble polymers (associative thickeners of the hydrophobically modified, ethoxylated urethane [HEUR] type). Particle image velocimetry (PIV) profiles are considered in the perspective of the dynamic uniaxial extensional viscosity (DUEV) of the coatings and an effort to understand the results in terms of the structural aspects of the thickener molecules is undertaken. A high-M v hydroxyethyl cellulose (HEC) thickened formulation, with a significant DUEV, does not atomize well. Among the HEUR thickeners, the addition of larger hydrophobes in the terminal positions requires less thickener to achieve a 90 KU viscosity and produces lower DUEVs and lower viscosities at high-shear rates. This is necessary to produce formulations with acceptable spray characteristics (i.e., good atomization). The sprayability of these systems is reflected in their velocity profiles and particle size/particle size distributions. Poorer spray characteristics are reflected in ligaments and broad particles size distributions. This study highlights the ability to control the particle size/ size distribution and velocity profiles of coatings formulations through the use of structurally different HEUR associative thickeners. Variations in sprayability among different nozzle geometries are also studied.

Spray applications: Part V. Influence of high solid compositions on coatings sprayability

“…4 The time between frames, Dt, was kept at 100 ls. The interrogation region was a 64 · 64 mm square selected to give approximately 10-15 particles per interrogation region.…”

“…[23][24][25] In the 1:3:3 formulation, thicker ligaments and a greater number of larger drop sizes are evident, similar to the spray patterns seen in latex paints with moderate DUEVs. 4 With increasing deformation rates, extensional viscosities are known to increase and if formulations around the 1:2:4 ratios had been studied, high extensional viscosities may have been measurable, despite its Newtonian shear viscosity behavior. The particle velocity patterns for the four formulations that provided spray patterns are illustrated in Fig.…”

Vegetable oil based fatty amide as hydrophobes in associative thickener

“…1 Associative thickeners employed in waterborne coatings include cellulose derivatives, hydrophobically modified alkali soluble emulsions (HASE), and hydrophobically modified ethoxylated urethanes (HEURs). Hydrophobically modified cellulosics, 1,6 acrylics, 1,7,8 and urethanes 1,7,[9][10][11] constitute the building block materials for such associative thickeners. The associative thickening mechanism is primarily due to interactions between the hydrophobic portions of thickener and latex particles, but is also influenced by surfactants, coalescing solvents, and pigments.…”

“…HEURs consist of polyethylene oxide (PEO) blocks linked via urethane moieties and end-capped with long alkyl chains such that the PEO blocks act as hydrophilic segments and the long alkyl chains function as flexible hydrophobes. [9][10][11][12] Commercial HEUR rheology modifiers are currently based on petroleum derivatives. In this study, vegetable oil derivatives were synthesized to function as hydrophobes in the bio-based HEURs.…”

Na-Bentonite and MgO Mixture as a Thickening Agent for Water-Based Paints

“…Thus close attention must be paid to dispersant, thickener and pigment types to achieve optimum paint properties 9) .Hydrophobically modified ethoxylated urethane [HEUR] and hydroxyethyl cellulose (HEC), which are used in water based paints have considerable effect on paint rheology. In particular different spray angles and nozzle geometries 10) dictate the type and amount of thickeners. The interaction of associative (HEUR type) and non-associative thickeners (HEC) with the rest of additives in paints emphasizes the role of latex particle size, surfactant type, amount and type of the thickener used in the water borne paint systems [11][12][13][14] .…”