A Novel High-Gradient Permanent Magnet for the Profiling of Planar Films and Coatings

Glover, PM; Aptaker, P.S.; Bowler, John R.; Ciampi, Elisabetta; McDonald, P.J.

doi:10.1006/jmre.1999.1772

Cited by 129 publications

(109 citation statements)

References 9 publications

(13 reference statements)

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“…The design of the GARField magnet has been described elsewhere. 39,40 The latex sample in a laminated basin was placed horizontally between the curved pole pieces above the radio-frequency (RF) coil used to excite and detect the NMR signal, as is shown in Figure 1. There is a static magnetic field strength, B 0 of 0.7 T in the horizontal direction parallel to the sample plane and a magnetic field gradient strength of 17.5 T m -1 in the direction perpendicular to the sample plane.…”

Section: Atomic Force Microscopy (Afm)mentioning

confidence: 99%

Correlating Particle Deformation with Water Concentration Profiles during Latex Film Formation: Reasons That Softer Latex Films Take Longer to Dry

et al. 2014

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During the past two decades, an improved understanding of the operative particle deformation mechanisms during latex film formation has been gained. For a particular colloidal dispersion, the Routh-Russel deformation maps predict the dominant mechanism for particle deformation under a particular set of conditions (evaporation rate, temperature, and initial film thickness). Although qualitative tests of the Routh-Russel model have been reported previously, a systematic study of the relationship between the film formation conditions and the resulting water concentration profiles is lacking. Here, the water Published in Langmuir (2014), vol, 30, pp 9672-9681 2 distributions during the film formation of a series of acrylic copolymer latexes with varying glass transition temperature, T g (values of 22, 11, 4 and 19 ºC) have been obtained using GARField nuclear magnetic resonance profiling. A significant reduction in the rate of water loss from the latex copolymer with the lowest T g was found, which is explained by its relatively low polymer viscosity enabling the growth of a coalesced skin layer. The set of processing parameters where the drying first becomes impeded occurs at the boundary between the capillary deformation and the wet sintering regimes of the Routh-Russel model, which provides strong confirmation of the model's validity. An inverse correlation between the model's dimensionless control parameter and the dimensionless drying time is discovered, which is useful for the design of fast-drying waterborne films.

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Section: Atomic Force Microscopy (Afm)mentioning

confidence: 99%

Correlating Particle Deformation with Water Concentration Profiles during Latex Film Formation: Reasons That Softer Latex Films Take Longer to Dry

et al. 2014

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“…The magnet's design has been described elsewhere [16]. Blends of PIDA latex and an acrylic latex with a larger particle size were cast and dried with known Peclet values.…”

Section: Garfield Nmrmentioning

confidence: 99%

Autostratification in Drying Colloidal Dispersions: Experimental Investigations

et al. 2012

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In films cast from a colloidal dispersion comprised of two particle sizes, we experimentally examine the distribution of particles normal to the substrate. The particle concentrations at various positions in the film are determined through atomic force microscopy and NMR profiling. The results are compared to a previously derived diffusional model. Evidence for diffusional driven stratification is found, but the importance of other flows is also highlighted. The conditions that enhance particle stratification are found to be a colloidally stable dispersion, low initial volume fractions, a low concentration of the stratifying particle and for the Peclet numbers of the two components to straddle unity.

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“…7,18 Briefly, the drying film is situated in a magnetic field gradient that is normal to plane of the substrate (Fig. 2).…”

Section: Magnetic Resonance Profilingmentioning

confidence: 99%

“…In order to explore skin formation in colloidal dispersions, we have simultaneously applied magnetic resonance profiling (MRP) 18,19 and diffusion wave spectroscopy (DWS) 20 to drying polymer films. There have been limited previous applications of light scattering techniques to studies of film formation, 21,22 and there are no previous reports of MRP and DWS being used together in such a study.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Drying of Colloidal Polymer Films: Dependence on Added Salt

et al. 2008

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Using magnetic resonance profiling coupled with dynamic light scattering, we have investigated the mechanisms leading to the formation of a partly coalesced surface layer, or "open skin", during film formation from waterborne polymer dispersions. We present the first use of the skewness of the distribution of free water as a model-free indicator of the spatial non-uniformity of drying. The skewness reaches a maximum at the same time at which a strong, static component -presumably originating from a skin at the film/air interface − appears in the light scattering data. The average solids content at this time is around 53 vol.%. Addition of salt to the dispersion increases both the skewness of the distribution of free water and the propensity for skin formation. Surprisingly, the drying is influenced not only by the concentration and valency of the ions in the salt but also by the particular ion. At intermediate particle densities, added salt strongly lowers the cooperative diffusion coefficient, D coop . When the particles reach close packing, D coop sharply increases. If the particles readily coalesce, the effects of the increased diffusivity will be counteracted, thereby inducing the formation of a skin. A modified Peclet number, Pe, using D coop , is proposed, so that the presence of salt is explicitly considered. This modified Pe is able to predict the non-uniformity in

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A Novel High-Gradient Permanent Magnet for the Profiling of Planar Films and Coatings

Cited by 129 publications

References 9 publications

Correlating Particle Deformation with Water Concentration Profiles during Latex Film Formation: Reasons That Softer Latex Films Take Longer to Dry

Correlating Particle Deformation with Water Concentration Profiles during Latex Film Formation: Reasons That Softer Latex Films Take Longer to Dry

Autostratification in Drying Colloidal Dispersions: Experimental Investigations

Heterogeneous Drying of Colloidal Polymer Films: Dependence on Added Salt

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