- Author
- Anderson, C. E., Jr. | Wauters, D. K.
- Title
- Intumescent Reaction Mechanisms: An Analytical Model. Final Report. July 1981-March 1983.
- Coporate
- Southwest Research Inst., San Antonio, TX
- Sponsor
- Naval Air Development Center, Warminster, PA
- Report
- NADC-82211-60; SWRI 6648/1; Work Unit CC110, May 1983, 130 p.
- Distribution
- Available from National Technical Information Service
- Contract
- N62269-81-C-0246
- Keywords
- intumescence | intumescent coatings | cook off | chemistry | paints | formulations | thermogravimetric analysis | mass loss | differential scanning | calorimeters | algorithms | equations | reaction kinetics | thermal conductivity
- Identifiers
- physical process; analytical modeling differential scanning calorimeter (DSC); model calculations; computational algorithms
- Abstract
- Intumescent coatings are used to protect a substrate, such as warheads, from heat sources, e.g., fires. When subjected to heat, various mechanisms are activated to dissipate the incident heat. Characteristic of intumescent systems is the evolution of gases in a pyrolysis zone which causes the coating to expand or inflate, i.e., intumescence. A char is formed which is generally graphitic and resistant to burning, and which also acts as a further thermal barrier because of its low thermal conductivity. A mathematical model has been devloped which describes the various physical process by considering mass and energy control volumes. Expansion is explicitly accounted for by assuming it to be a function of mass loss. Thermodynamic data from thermogravimetric analysis and differential scanning calorimeter has been written to solve the system of equations, with appropriate boundary conditions, as a function of time. Experimentally determined parameters such as mass loss as a function of temperature requires a Lagrangian formulation, but the computational grid is rezoned after each time step to re-establish an Eulerian grid for numerical accuracy in the difference equations. Mass loss, temperature, expansion velocities, etc., are computed. The model is exercised to determine the influence of various physical/chemical processes/constituents on the heat transfer to a substrate, and the model's predictions are compared against experimental data. Strengths and weaknesses of the model are delineated.