Prediction of the radiation term in the thermal conductivity of crosslinked closed cell polyolefin foams

Almanza, Ovidio; Rodríguez‐Pérez, Miguel Ángel; Saja, J.A. de

doi:10.1002/(sici)1099-0488(20000401)38:7<993::aid-polb10>3.0.co;2-j

Cited by 85 publications

(46 citation statements)

References 18 publications

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“…The contribution of radiation to the thermal properties has thus been evaluated for polymer [22][23][24] and carbon [25] foams. Though very useful, these empirical models contain adjustable parameters and are not able to give precise insight into the physics of heat transfer; structure-based or image-based modeling has therefore been undertaken in parallel with these correlations in order to extract more physical information.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of effective heat conductivities of foams by coupled conduction and radiation

Vignoles

Ortona

2016

International Journal of Thermal Sciences

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E↵ective thermal conductivities (ETC) under vacuum were computed numerically on 3D blocks of open-cell foams either obtained by X-ray tomography or generated by Computer-Aided Design (CAD) with ideal geometries.For the first time a Monte-Carlo/Random Walk code accounting for the coupling of conduction in the solid phase and of radiation in the pore space has been used. The whole range of conduction/radiation ratio, parameterized by a Nusselt number, has been scanned; a law relating the ETC to this parameter has been obtained. In all cases the conductive and radiative contributions are additive. The slope of the radiative contribution to the ETC is found to display a distinct behavior, depending on whether radiation or conduction dominates. The low-temperature regime has an emissivity-dependent ETC slope, while the high-temperature regime does not.The critical ratio between both regimes is related to the ratio between cell and strut diameters. In all cases, it is found that the ETC anisotropy decreases with temperature. Closing some windows enhances conduction parallel to the closing walls and reduces radiation perpendicular to them. This e↵ect is shown to influence the ETC eigendirections in actual media.

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Section: Introductionmentioning

confidence: 99%

Numerical study of effective heat conductivities of foams by coupled conduction and radiation

Vignoles

Ortona

2016

International Journal of Thermal Sciences

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“…The mixtures of known composition used are those obtained from freshly made foams for which the cell gas composition is known. In fact, the molar fraction of physical blowing agent and CO 2 (air is approximately absent) can be calculated using Eq 1 (where n g can be evaluated from foam formulation) and the following equation: (30) where x i ,PU is the molar fraction of component i (physical blowing agent or CO 2 ) in polyurethane foam, p 0,i is the initial partial pressure of component i, p 0,CO2 is the initial partial pressure of CO 2 and p 0,pba is the initial partial pressure of the physical blowing agent. A replicate series of mixtures of known composition is injected and the average area/unit amount of substance calculated:…”

Section: Gas Chromatographymentioning

confidence: 99%

New experimental method for determination of effective diffusion coefficient of blowing agents in polyurethane foams

Modesti

Lorenzetti

Dall'Acqua

2004

Polymer Engineering & Sci

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The effective diffusion coefficients of novel, environmentally friendly, hydrofluorocarbon (HFC) blowing agents for polyurethane foam production were measured. The method was based on gas chromatography and infrared spectroscopy measurements. The accuracy and reliability of the procedure developed were confirmed by comparisons of experimental and the predicted thermal aging curves. The slope of the aging curves (i.e., the change in thermal conductivity with time) depended only on the effective diffusion coefficients. The effective diffusion coefficients of the new HFC blowing agents were close to those of conventional hydrochlorofluorocarbon (HCFC) blowing agents, and the aging behavior of foams produced from HFC or HCFC blowing agents were similar

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“…Therefore, it is worthwhile to study the EMI SE of PUF with conductive fillers such as MWCNTs, carbon fiber, and graphite since studies on PUF have been focused mostly on its thermal insulating properties so far. [22][23][24][25][26][27] A low concentration of well-dispersed nanoparticles in the polyurethane matrix may produce a copious number of bubbles by reducing the activation energy required for nucleation. Recent studies have shown that nanoparticles effectively reduced the cell size of the PUF during the foaming process, which may affect the thermal properties of the PUF.…”

Section: Introductionmentioning

confidence: 99%

Electrical conductivity andEMIshielding effectiveness of polyurethane foam–conductive filler composites

Kim

Lee

Jang

et al. 2016

J of Applied Polymer Sci

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The morphological, electrical, and thermal properties of polyurethane foam (PUF)/single conductive filler composites and PUF/hybrid conductive filler composites were investigated. For the PUF/single conductive filler composites, the PUF/nickel‐coated carbon fiber (NCCF) composite showed higher electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) than did the PUF/multiwall carbon nanotube (MWCNT) and PUF/graphite composites; therefore, NCCF is the most effective filler among those tested in this study. For the PUF/hybrid conductive fillers PUF/NCCF (3.0 php)/MWCNT (3.0 php) composites, the values of electrical conductivity and EMI SE were determined to be 0.171 S/cm and 24.7 dB (decibel), respectively, which were the highest among the fillers investigated in this study. NCCF and MWCNT were the most effective primary and secondary fillers, and they had a synergistic effect on the electrical conductivity and EMI SE of the PUF/NCCF/MWCNT composites. From the results of thermal conductivity and cell size of the PUF/conductive filler composites, it is suggested that a reduction in cell size lowers the thermal conductivity of the PUF/conductive filler composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44373.

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Prediction of the radiation term in the thermal conductivity of crosslinked closed cell polyolefin foams

Cited by 85 publications

References 18 publications

Numerical study of effective heat conductivities of foams by coupled conduction and radiation

Numerical study of effective heat conductivities of foams by coupled conduction and radiation

New experimental method for determination of effective diffusion coefficient of blowing agents in polyurethane foams

Electrical conductivity andEMIshielding effectiveness of polyurethane foam–conductive filler composites

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