SPE Foams® 2021

Piyapong Buahom


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Piyapong Buahom, University of Toronto

Piyapong Buahom
Student
University of Toronto

Does A Largely Expanded Nanocellular Foam Really Exhibit Superinsulation By Knudsen Effect

Abstract: It has been believed that a low-density, nanocellular foam will have a superinsulation property through the Knudsen effect. This claim has never been proven to be effective because of the challenges in achieving a large expansion ratio from nanocellular foams. But this paper discusses a possibility that this is a wrong claim because of the increased radiation through the thin cell walls and thin struts. Closed-cell foam consisting of cell walls and struts was used as the base geometry for modeling. The mathematical correlations to calculate the thickness of cell walls and the diameter of struts for a given cell size, the void fraction and the volume fraction of polymer located in struts were investigated. Then, a mathematical model for the conductive thermal conductivity including the dependency on the void fraction, the strut fraction and the Knudsen effect for gas was introduced. The radiative thermal conductivity was determined by analyzing the attenuation of radiative energy by absorption and scattering based on Mie’s theory together with electromagnetic wave interference, as well as interference of propagating waves and tunneling of the radiative energy by evanescent waves in the cells. The thermal conductivity model was validated by experimental data and used to predict the thermal conductivity of polystyrene (PS) and poly(methyl methacrylate) (PMMA) foams at various cell sizes and volume expansion ratios. It was found that the radiative thermal conductivity plays a crucial role in nanocellular foam.

Biography: Piyapong Buahom is a Ph.D. student in Microcellar Plastics Manufacturing Laboratory (MPML) at University of Toronto, Canada. He completed his B.Eng. and M.Eng. in Chemical Engineering from King Mongkut’s Institute of Technology Ladkrabang in Bangkok, Thailand. He has experience in natural fibers reinforced polyurethane composite foams, natural rubber-based polyols, foam morphology characterization, cellular structure modeling, and heat transfer in porous materials. He has published 14 journal papers and 16 international conferences. Currently, his research focus is on modeling the correlation between the cellular structure and the thermal conductivity for thermal insulation materials.


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