Computer Tomography Based Structure Characterization of Expanded Intumescent Coatings for Fire Protection

Kang, Jiyuan; Takahashi, Fumiaki; T’ien, James S.

doi:10.1007/s10694-018-0796-x

Cited by 8 publications

(12 citation statements)

References 24 publications

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“…However, this procedure does not completely eliminate noise and the calculated porosities tend to be lower (typically below 50%) than what might be expected for the reported expansion factors. 20,21,26 Similar procedures were also reported for SEM images, but the performance of such an approach was very limited. 27 Here, the raw data was simply uploaded to the ilastik software package 37 (see the Materials and Methods for details) and binarized by training the machine learning algorithm.…”

Section: ■ Materials and Methodsmentioning

confidence: 86%

“…Difficulties in analyzing intumescent char structures with CT were previously reported and explained by the low atomic number of the carbonaceous material and potential air voids below the CT resolution limit within the solid phase. 20,22,23,26 A common procedure to improve the noisy and low-contrast CT data would be to modify the brightness or apply some kind of contrast enhancement or noise reduction filter. 8,26 Subsequently, image thresholding would lead to the binary image.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…For example, Morys et al ,− compared chars qualitatively by looking at gray-scale values from their CT data to identify relative changes in char density. Kang et al , calculated char porosities from their CT data. However, the calculated values were generally below 50% (similar values were obtained by others , ).…”

Section: Introductionmentioning

confidence: 99%

“…10–20, rendering a porosity below 50% as rather unlikely. A possible reason for this discrepancy might be that pores below the voxel size of about 100 μm were not included in the porosity calculations. , The authors also calculated pore size distributions and pore sphericities, but given the limited CT resolution, small pores were likely missed.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Quantitative Characterization of Highly Porous Structures with Fluorescence Microscopy and Microcomputed Tomography

Dreyer

Gundlach

Weinell

et al. 2021

Ind. Eng. Chem. Res.

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In this study, a rapid and versatile methodology for quantitative pore structure characterization is described taking the example of intumescent char. The char porosity and pore structure tend to be difficult to quantify but are decisive for the material’s thermal conductivity and thus performance. The methodology described here uses a fluorescent dye containing epoxy to impregnate the char. After curing, the sample is cut and polished, followed by imaging with a fluorescence microscope. The recorded images are segmented using an open-source interactive machine learning program, followed by automated pore size and porosity measurements. Volume-based three-dimensional (3D) pore size distributions are calculated via stereography and compared to X-ray microcomputed tomography (μ-CT) results. The pore aspect ratio and tortuosity of the solid char phase are also discussed. It is shown that the fluorescence microscopy methodology produces high-resolution images with excellent contrast, while similar pore metrics (porosity of 81.8%, average volume-based pore size of 70.5 μm) to those for μ-CT are obtained.

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Section: ■ Materials and Methodsmentioning

confidence: 86%

Section: ■ Materials and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Quantitative Characterization of Highly Porous Structures with Fluorescence Microscopy and Microcomputed Tomography

Dreyer

Gundlach

Weinell

et al. 2021

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

show abstract

“…Indeed, the resolution of regular CT was 81 μm/pix (against 2 to 10 μm/pix in optical method), so, CT was not capable of probing the micro porosity even though the micro (fractal) tortuosity was reasonably detected. Thereby, in color contrasted images, the image computed void ratio is far more realistic than the literature values given by computed tomography [8,23]. So, the color contrast method could be improved in the future as a rapid complementary tool to the measurements of apparent density properties on fire tested residues.…”

Section: Resultsmentioning

confidence: 99%

A Facile Technique to Extract the Cross-Sectional Structure of Brittle Porous Chars from Intumescent Coatings

et al. 2019

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Intumescent coatings are part of passive fire protection systems. In case of fire, they expand under thermal stimuli and reduce heat transfer rates. Their expansion mechanisms are more or less recognized, but the fire testing data shall be interpreted as function of coating morphology. Expansion ratios are examined together with the inner structures of specimens submitted to fire. Bare cutting techniques damage the highly porous and fibrous specimens because they become very crumbly due to charring. So far, absorption contrasted X-ray computed microtomography (CT) was used as a non-destructive technique. Nevertheless, access to X-ray platforms can be relatively expensive and scarce for regular use. Also, it has some drawbacks for carbon rich specimens strongly adhering on steel substrates because it leads sometimes to noisy images and lost data due to resolution limits on specimens reaching ten of centimeters. Therefore, we propose an inexpensive and more accessible experimental approach to observe those specimens with minimized structural damage under visible lighting. To that end, charred specimens were casted into pigmented epoxy resin. After surface treatments, color contrasted cross-sections could be observed under optical digital microscopy thanks to high level of interconnectivity of pores. Subsequent image treatments confirmed that the structural integrity was kept when compared to previous CT data. The proposed method is practical, cheaper and more accessible for the quantitative assessment of inner structure of charred brittle specimens.

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The CoaST‐Fire: A novel methodology to rapidly expose materials to various fire curves

et al. 2022

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A new method for testing materials under simulated fire conditions is introduced.The fundamentally new approach relies on the movement of the sample through zones with a spatially increasing temperature. Adjusting the velocity profile with which the sample is moved makes it possible to expose it to practically any temperature-time curve defined in fire safety standards, from extremely rapid hydrocarbon to more gradual cellulosic fire conditions. This manuscript presents a prototype named CoaST-Fire that capitalises on this concept by combining a vertical tube furnace with a vertical motion system. The methodology to calibrate the furnace temperature profile, as well as to calculate the velocity profiles are discussed. The velocity profiles are then used to replicate a range of temperature-time curves with exceptional accuracy and reproducibility. A numerical model is developed in COMSOL Multiphysics to study heat fluxes towards the steel substrate as a function of time and thermal insulation. Finally, proof-of-concept experiments with two commercial intumescent coatings are presented. The experiments are shown to be highly repeatable while images of the coatings during the experiments can provide additional insights into the occurring reaction steps. Furthermore, CoaST-Fire makes it possible to conduct experiments under various O 2 concentrations and could later be extended with a gas outlet analysis system. The study is in line with recent efforts to develop cheaper and more rapid testing methods for early research and development of intumescent coatings and the setup could potentially also be used to test other types of materials.

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Computer Tomography Based Structure Characterization of Expanded Intumescent Coatings for Fire Protection

Cited by 8 publications

References 24 publications

Quantitative Characterization of Highly Porous Structures with Fluorescence Microscopy and Microcomputed Tomography

Quantitative Characterization of Highly Porous Structures with Fluorescence Microscopy and Microcomputed Tomography

A Facile Technique to Extract the Cross-Sectional Structure of Brittle Porous Chars from Intumescent Coatings

The CoaST‐Fire: A novel methodology to rapidly expose materials to various fire curves

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