A STATISTICAL NETWORK MODEL FOR POLYMER DEGRADATION

THE SUBSTITUTION OF POLYMERS FOR METALS AND OTHER MATERIALS IS OCCURRING AT AN INCREASING RATE IN SEVERAL U.S. INDUSTRIES (E.G., AUTOMOTIVE, AEROSPACE, COMPUTER). THE MOTIVATION IS THAT POLYMERS OFTEN HAVE SIGNIFICANT ADVANTAGES IN TERMS OF WEIGHT AND/OR COST. HOWEVER, THE DEGRADATION OF POLYMERS IS A LIMITING FACTOR IN MANY APPLICATIONS. THE THERMAL DEGRADATION OF POLYMERS IS AN IMPORTANT ISSUE IN POLYMER PROCESSING AND IN FIRE SAFETY, WHILE THE BIODEGRADATION BEHAVIOR IS AN IMPORTANT ENVIRONMENTAL CONCERN. TO DESCRIBE THE DEGRADATION OF POLYMERS, ONE NEEDS TO KNOW THE CHEMICAL REACTIONS AND RATESFOR THE BOND BREAKING AND CROSSLINKING REACTIONS. BUT THESEREACTIONS TYPICALLY OCCUR WITHIN A CROSSLINKED MACROMOLECULAR NETWORK, SO THEIR EFFECTS IN FRAGMENTING THE MACROMOLECULE MUST BE TREATED STATISTICALLY. IN ADDITION, EFFECTS OF HEAT AND MASS TRANSPORT WITHIN A MATERIAL UNDERGOING PHASE CHANGES MUST ALSO BE INCLUDED. DURING THE PAST TEN YEARS, ADVANCED FUEL RESEARCH, INC. (AFR) HAS CONDUCTED RESEARCH ON MODELING THE PYROLYSIS OF COAL, A NATURAL POLYMER, WHICH HAS LED TO DEVELOPMENT OF A MACROMOLECULAR NETWORK MODEL (FG-DVC) TO DESCRIBE THE THERMAL DECOMPOSITION OF COAL. THIS PROPOSAL SUGGESTS THE EXPANSION, IMPROVEMENT AND APPLICATION OF THE FG-DVC MODEL AS A GENERAL COMPUTATIONAL TECHNIQUE TO SIMULATE POLYMER DEGRADATION. IN PHASE I WE WILL SELECT THREE POLYMER SYSTEMS WHICH HAVE BEEN WELL STUDIED ELSEWHERE AND WHICH AREREPRESENTATIVE OF IMPORTANT CLASSES OF POLYMERS. THESE POLYMERS WILL BE CHARACTERIZED TO DETERMINE THE REACTIONS, RATES AND COMPOSITION PARAMETERS FOR THE MODEL. WE WILL USETHE PREVIOUS DATA OBTAINED FOR THESE POLYMERS, AND IN ADDITION, WE WILL CHARACTERIZE THEM IN OUR LABORATORY USING TG-FTIR, QUANTITATIVE FT-IR SPECTROSCOPY, SOLVENT EXTRACTION, SOLVENT SWELLING AND FIELD IONIZATION MASS SPECTROMETRY (FIMS) TO DETERMINE THE MODEL INPUT PARAMETERS. THESE WERE THE TECHNIQUES USED TO OBTAIN THE FG-DVC PARAMETERS FOR COAL. THE POLYMERS' CHARACTERISTICS WILL THEN BE USED IN THE FG-DVC MODEL (MODIFIED WHERE NECESSARY) TO SIMULATE THEIR THERMAL DECOMPOSITION. THE SIMULATIONS WILL BE COMPARED TO THE LITERATURE DATA. IN PHASE II, WE WILL EXPAND THE TEST CASES TO INCLUDE A WIDER RANGE OF POLYMERS, SIMULTANEOUS HEAT AND MASS TRANSPORT EFFECTS, AND ADDITIONAL DEGRADATION REACTIONS OF PRACTICAL IMPORTANCE INCLUDING OXIDATION, UV INDUCED DEGRADATION AND BIODEGRADATION.