CPUF - a chemical-structure-based polyurethane foam decomposition and foam response model.

Fletcher, Thomas H. (Brigham Young University, Provo, UT) ; Thompson, Kyle Richard ; Erickson, Kenneth L. ; Dowding, Kevin J. ; Clayton, Daniel (Brigham Young University, Provo, UT) ; Chu, Tze Yao ; Hobbs, Michael L. ; Borek, Theodore Thaddeus III

Sandia National Laboratories

关键词: Equilibrium;    Polyurethanes;    Foam.;    Polyurethanes.;    Validation Foam.;   

DOI  :  10.2172/917122
RP-ID  :  SAND2003-2282
RP-ID  :  AC04-94AL85000
RP-ID  :  917122

美国|英语

来源: UNT Digital Library

【 摘 要 】

A Chemical-structure-based PolyUrethane Foam (CPUF) decomposition model has been developed to predict the fire-induced response of rigid, closed-cell polyurethane foam-filled systems. The model, developed for the B-61 and W-80 fireset foam, is based on a cascade of bondbreaking reactions that produce CO2. Percolation theory is used to dynamically quantify polymer fragment populations of the thermally degrading foam. The partition between condensed-phase polymer fragments and gas-phase polymer fragments (i.e. vapor-liquid split) was determined using a vapor-liquid equilibrium model. The CPUF decomposition model was implemented into the finite element (FE) heat conduction codes COYOTE and CALORE, which support chemical kinetics and enclosure radiation. Elements were removed from the computational domain when the calculated solid mass fractions within the individual finite element decrease below a set criterion. Element removal, referred to as ?element death,? creates a radiation enclosure (assumed to be non-participating) as well as a decomposition front, which separates the condensed-phase encapsulant from the gas-filled enclosure. All of the chemistry parameters as well as thermophysical properties for the CPUF model were obtained from small-scale laboratory experiments. The CPUF model was evaluated by comparing predictions to measurements. The validation experiments included several thermogravimetric experiments at pressures ranging from ambient pressure to 30 bars. Larger, component-scale experiments were also used to validate the foam response model. The effects of heat flux, bulk density, orientation, embedded components, confinement and pressure were measured and compared to model predictions. Uncertainties in the model results were evaluated using a mean value approach. The measured mass loss in the TGA experiments and the measured location of the decomposition front were within the 95% prediction limit determined using the CPUF model for all of the experiments where the decomposition gases were vented sufficiently. The CPUF model results were not as good for the partially confined radiant heat experiments where the vent area was regulated to maintain pressure. Liquefaction and flow effects, which are not considered in the CPUF model, become important when the decomposition gases are confined.