The role of sag control agents in optimizing the sag/leveling balance and a new powerful tool to study this

Bosma, M.; Brinkhuis, R.H.G.; Coopmans, Jo; Reuvers, Bart

doi:10.1016/j.porgcoat.2005.08.008

Cited by 34 publications

(7 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Orchard's approach allows one to compute the decay rate of a sinusoidal disturbance on a film, where the disturbance wavelength (k) is large compared to the initial film depth, (h 0 ). 4,8 Thus, the change in height of a disturbance can be computed over time by using…”

Section: Modeling Resultsmentioning

confidence: 99%

“…4 This work was later extended by Overdiep and others who elucidated the role of surface tension gradients during the drying of brush-applied coatings. [5][6][7][8] In this case, it was shown that surface tension gradients arise due to the differential fraction of solvent that is lost in thin versus thicker sections of the wet film. As the solvent typically has a lower surface energy than the binder, the concentration gradients result in surface energy gradients that give rise to a flow of material due to the creation of surface shear stresses.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The evolution of surface texture in automotive coatings

2011

View full text Add to dashboard Cite

The curing behavior and texture development of automotive clearcoats was studied by noncontacting profilometry and dynamic viscosity measurements during solvent evaporation and thermal curing. The changing surface texture was shown to be a strong function of temperature and solvent content. Leveling occurred during the initial heating of the clearcoats, while smaller wavelength roughness was observed to appear during cooling after curing. The dynamic viscosity was shown to be a strong function of catalyst loading. Numerical simulations were conducted to calculate the apparent viscosity during the leveling process. Calculated viscosity profiles matched theoretical predictions for the behavior of these clearcoats.

show abstract

Section: Modeling Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The evolution of surface texture in automotive coatings

2011

View full text Add to dashboard Cite

show abstract

“…where the term on the right represents the area under the experimental fluidity-time curve from simulated application until (effectively) infinite viscosity is reached. Bosma et al 50,51 asserted that equation ( 10), which they term the ''averaged paint fluidity,'' is not adequate for correlating sagging and leveling behavior. They defined a ''total film fluidity'' integral W(¥) [equation (11)] which incorporates the cube of the time-dependent wet-film thickness h(t).…”

Section: Levelingmentioning

confidence: 99%

Applied rheology and architectural coating performance

Eley

2019

J Coat Technol Res

View full text Add to dashboard Cite

Paint rheology is understood to play a vital role in both product performance and customer acceptance. Consequently, the ability to formulate paints having the necessary flow properties is essential for paint technologists. Experienced formulators have said that as much as half the cost of new product development can be consumed in getting the rheology right. In fact, the quality-control viscosity measurement devices in everyday use in the development laboratory are of little help in this endeavor. Among other shortcomings, most such instruments apply shear stresses which are far from those involved in important coating flow processes. The rheological properties required for a successful coating must be defined with due regard to the prevailing conditions of stress involved in application and film formation. This requires that measurements should be taken over a wide range of shear stress and timescales. The task for the applied rheologist is to bridge rheology and technology, but it is often unclear how to connect rheological data with the ''real-world'' performance of paints, due to the complexity of coating flows. This review in part discusses the use of controlled-stress rheometry to characterize coatings, and presents ways of applying the results effectively to the analysis of paint flow. The methodology is fundamental but not unduly time-consuming, since the objective is to provide sound yet timely guidance to formulators. Thirteen commercial semigloss latex paints were analyzed rheologically to develop correlations to paint performance. Using the method of shear stress map-ping, key regions of the non-equilibrium flow curve are identified for the control of paint flow processes. With this approach, simple but strong correlations were obtained of paint flow metrics to viscosity chosen at the relevant stresses. The fact of high correlation means one can expect that an appropriate viscosity adjustment will correspondingly improve performance. It is argued that shear stress, not shear rate, is the correct independent variable both for experimentation and for the graphical presentation and analysis of viscosity data. The yield stress parameter, particle flocculation, and sedimentation are also discussed, and an oscillatory shear method of direct measurement of yield stress is described.

show abstract

“…The change with time of the rheological properties of pharmaceutical formulations may influence the controlled release of loaded drugs, defining their therapeutic efficacy and bioavailability [6]. In colloid science, the decrease of viscosity of gels and suspensions of colloidal particles when shear is applied make them key components in mining, ceramic, and coating industries [7,8,9,10,11]. Moreover, time dependent colloidal gels are an emerging alternative in biotechnology for cell culture [12] and in rocket propulsion systems [13,14,15].…”

Section: Introductionmentioning

confidence: 99%

Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels

Santos

Carignano

Campanella

2017

Gels

View full text Add to dashboard Cite

This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7%) and a hydrophobic solvent (Hydrocarbon fuel, JP-8). Viscosity measurements as a function of time were carried out at different shear rates (10, 50, 100, 500, and 1000 s −1 ), and based on this data, a new structural kinetics model was used to describe the system. Previous work has based the analysis of time dependent fluids on the viscosity of the intact material, i.e., before it is sheared, which is a condition very difficult to achieve when weak gels are tested. The simple action of loading the gel in the rheometer affects its structure and rheology, and the reproducibility of the measurements is thus seriously compromised. Changes in viscosity and viscoelastic properties of the sheared material are indicative of microstructural changes in the gel that need to be accounted for. Therefore, a more realistic method is presented in this work. In addition, microscopical images (Cryo-SEM) were obtained to show how the structure of the gel is affected upon application of shear.

show abstract

The role of sag control agents in optimizing the sag/leveling balance and a new powerful tool to study this

Cited by 34 publications

References 10 publications

The evolution of surface texture in automotive coatings

The evolution of surface texture in automotive coatings

Applied rheology and architectural coating performance

Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels

Contact Info

Product

Resources

About