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Some aspects of autoignition delays and flammability limits of polyurethane based on diphenyl methane diisocyanate (MDI) and propoxylated trimethylol propane
Author(s) -
Gaboriaud F.,
Vantelon J. P.,
Breillat C.
Publication year - 1985
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1985.070300902
Subject(s) - propane , autoignition temperature , polyurethane , ignition system , flammability , induction period , combustion , oxidizing agent , methane , flammability limit , materials science , chemistry , chemical engineering , thermodynamics , polymer chemistry , organic chemistry , catalysis , physics , engineering
The main purpose of this work is a better understanding of the physicochemical phenomena involved during an unpiloted ignition. We intend to characterize the step corresponding to the degradation of the material, the production of combustible gases, and their combustion with the surrounding oxidizing gas, leading to the flame. The degradation gases which are essentially alkanes, alkenes, and aldehydes undergo oxidation by degenerate chain branching mechanism. The initiating chain propagates very quickly and creates intermediate species of increased stability which initiate new active centers leading to secondary chains. Then, ignition can occur after a relatively large induction period. We suggest that this period may be defined as the time to reach a critical rate of production of the intermediate species. A study of the active center distribution near the surface as a function of time and of the distance to the surface allows us to explain the experimental variation of ignition delays vs. oxidant pressure. The ignition limits of this polyurethane, i.e., temperature–pressure curves in air and in oxygen, have also been determined. It has been possible to correlate pressure and temperature and to specify the influence of nitrogen on the ignition process.