A novel technique for in situ measurements of stress development within a drying film

Chen, Jianshe; Ettelaie, Rammile; Hong-yuan, Yang; Yao, Lin

doi:10.1016/j.jfoodeng.2008.12.009

Cited by 3 publications

(6 citation statements)

References 14 publications

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“…A diagram of the setup and the details of the procedure can also be found in a previous study in which the development of stress within drying films was studied. 7 The coated beam was then placed on a balance inside the chamber, and the weight loss was monitored in situ at set time intervals for 4 h.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…This pressure imbalance results in the buildup of mechanical stress within the film, which leads to possible shrinkage, collapse, or cracking of the film to release the stress. The increase of stress and its subsequent decrease as a result of structural relaxation within a drying film have been experimentally measured by our group . The dynamics of stress evolution within the film depends significantly on the internal structure of the film.…”

Section: Introductionmentioning

confidence: 99%

“…The increase of stress and its subsequent decrease as a result of structural relaxation within a drying film have been experimentally measured by our group. 7 The dynamics of stress evolution within the film depends significantly on the internal structure of the film. Cracking of the film is most prevalent in the drying of colloidal particulate dispersions or solutions of film-forming polymers below their glass transition temperature, where the structural relaxation times are long.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of Food Biopolymer Film Dehydration: Experimental Studies and Mathematical Modeling

Ettelaie

Tasker

Chen

et al. 2013

Ind. Eng. Chem. Res.

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The dehydration process in thin biopolymer-based films, involving the two main macromolecules in food systems, namely, proteins and polysaccharides, has been investigated. Experimental measurements of the weight loss of polymer films were carried out in an enclosed Perspex chamber under controlled conditions of temperature, relative humidity, and air flow. We found that all of the experimental moisture ratio data for films of pure biopolymers, as well as their mixtures, can be superimposed on a single scaled dehydration curve. According to theoretical calculations, this curve cannot be described by a moisture diffusion-dominated drying process, irrespective of whether film shrinkage is included or ignored. We also derived an analytical expression for evaporation-controlled drying. When film shrinkage is fully taken into account in the calculations, very good agreement between the experiments and the theoretically derived curve is obtained. However, the theoretical results can be improved even further by considering a model that includes both diffusion and evaporation processes, with diffusion being fast but nonetheless finite, so as to only play a minor secondary role in the dehydration of such films. Theoretical models have also been extended to describe systems in which film shrinkage can also arise from changes in the partial molar volume and not just loss of moisture. Using a variable "effective" partial molar volume for water provides a possible method for modeling the entire drying process over different stages of dehydration in which the solid phase adopts significantly contrasting structures.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinetics of Food Biopolymer Film Dehydration: Experimental Studies and Mathematical Modeling

Ettelaie

Tasker

Chen

et al. 2013

Ind. Eng. Chem. Res.

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“…Deflection of such cantilevers has been used to monitor stress development during drying. 24,25 Here we introduce a novel micro-cantilever method for the direct measurement of stresses in spin-cast polymer films. Focused ion-beam (FIB) milling was used to cut cantilevers from polymer-coated silicon nitride (SiN) membranes.…”

Section: Introductionmentioning

confidence: 99%

Direct stress measurements in thin polymer films

Thomas

Steiner

2011

Soft Matter

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Stresses in thin polymer films were quantitatively determined by measuring the deflection of a cantilever cut from a film-covered silicon nitride membrane using a focused ion beam. Spin-cast high molecular weight films showed a surprisingly high residual stress, which by far exceeded the tensile strength of the bulk polymer. Thermal annealing relaxed these stresses suggesting two relaxation mechanisms, both of which are much faster than the reptation time. ExperimentalPolystyrene (PS) M w ¼ 4000 kg mol À1 , M w /M n ¼ 1.15 (Polymer Standards Service) was used as obtained. 100 nm thick films were

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“…Research by Francis et al also illustrates that the cantilever technique has been used for stress measurements with solvent-based polymer coatings. , Other researchers have also employed this beam-bending technique to measure stresses in calcium carbonate−latex coatings, , alumina−latex suspensions, , silica−latex suspensions, and biopolymer fluids . In this article, we investigate the stress evolution in a latex film for a range of conditions below and above the minimum film-formation temperature (MFFT).…”

Section: Introductionmentioning

confidence: 99%

Evolving Stresses in Latex Films as a Function of Temperature

et al. 2010

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Latex films were dried on a flexible substrate, and the substrate deflection was monitored over time to give an averaged film stress-evolution profile. Films were dried at various temperatures below and above the minimum film-formation temperature of the latex dispersion. The effect of polymer rheology, which is a temperature-dependent parameter, on film formation, was investigated. The reliability of the Stoney model in predicting film stress from substrate curvature was also examined and compared to the Euler-Bernoulli model. It was shown that the linearized Stoney model was unsuitable for the larger measured stresses.

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A novel technique for in situ measurements of stress development within a drying film

Cited by 3 publications

References 14 publications

Kinetics of Food Biopolymer Film Dehydration: Experimental Studies and Mathematical Modeling

Kinetics of Food Biopolymer Film Dehydration: Experimental Studies and Mathematical Modeling

Direct stress measurements in thin polymer films

Evolving Stresses in Latex Films as a Function of Temperature

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