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Three-Dimensional Kinetic Model for the Swelling of Intumescent Materials (NISTIR 5499)



Kathryn M. Butler, Howard R. Baum, Takashi Kashiwagi


An intumescent coating protects the underlying surface from fire by swelling into a thick insulating char. Design of intumescent materials has proceeded largely by systematic testing of a variety of formulations, since the mechanisms of physical, thermal and chemical behavior are not as yet well understood. Previous models of intumescent behavior have treated the system as a one-dimensional heat transfer problem through a coating consisting of a char layer and a layer of virgin material separated by a thin pyrolysis zone. In this work, a fully three-dimensional, time-dependent numerical model combining the dynamics of the swelling process, the heat transfer through the coating, and the chemistry of gasification is described.
NIST Interagency/Internal Report (NISTIR) - 5499
Report Number


fire research, intumescent coatings, kinetics, swelling, heat transfer, gasification, fire models


Butler, K. , Baum, H. and Kashiwagi, T. (1994), Three-Dimensional Kinetic Model for the Swelling of Intumescent Materials (NISTIR 5499), NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed July 20, 2024)


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Created September 1, 1994, Updated November 10, 2018