1. Chemistry Department, State University of New York, Stony Brook, New York 11794-3400; Chemical Engineering Department, West Virginia University, Morgantown, West Virginia 26506; Materials Science and Engineering Department, State University of New York, Stony Brook, New York 11794; Central Research and Development, DuPont Company, Wilmington, Delaware 19880; and Fire Research Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665