Date of Award
Spring 2005
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Wilkie, Charles A.
Second Advisor
Yi, Chae S.
Third Advisor
Steinmetz, Mark G.
Abstract
In general, fire retardancy is evaluated in terms of either self-extinguishing properties or the reduction in heat release rate. Since there is a close relationship between thermal degradation behavior of polymer and its fire retardancy, this dissertation mainly deals with the degradation behavior of fire retardant formulations. Part I is focused on the thermal degradation behavior of polycarbonate and polycarbonate/aryl-phosphate blends. Polycarbonate is one of commonly used engineering plastics and its fire retardant formulations are continuously expanding in the past few decades due to its excellent mechanical properties. Nonetheless, there is no systematic study explaining how and why effective self-extinguishing fire retardancy is achieved when conventional fire retardants are incorporated with polycarbonate, from the viewpoint of degradation behavior based on the analysis of degraded products. Thus, in Part I, the thermal degradation of polycarbonate is carried out and scrutinized in various environments to simulate a real combustion with/without fire retardant using TGA/FTIR, GC/MS etc. If there is a heat source causing a fire, any polymer systems eventually bums, even self-extinguishing fire retardant compositions. In this aspect, polymer/clay nanocomposites provide another promising property in the area of fire retardancy, because the heat release rate during burning is dramatically reduced during combustion. In other words, less heat emission from polymer nanocomposites in a fire is accomplished as compared with that of virgin polymer. Especially, the clay nanocomposites of polystyrene, polyarnide 6 and poly(ethylene-co-vinylacetate) exhibit a large reduction in peak heat release rate (PHRR) in the cone calorimeter. It is felt that this result must be related to the degradation behavior of the polymers, because some polymer systems do not exhibit a significant reduction in PHRR. Therefore, in Part II, how the degradation pathway of polymer is modified in the presence of clay by forming nanocomposite is discussed using the same technique as in Part I. The polymers used in this study are polystyrene, polyamide 6, poly(styrene-co-acrylonitrile) and acrylonitrilebutadiene- styrene terpolymer. The dominant properties of polymer-clay nanocomposite are achieved when the clay layers are evenly distributed in a polymer matrix at the nanometer-scale, providing a huge interfacial area between polymer matrix and the clay surface. In Part III, the relationship between the solubility parameter of polymer and the clay dispersion in polymer-clay nanocomposites is explored based on a model study and previous results to suggest a criterion for the clay morphology. The concept of solubility parameter is introduced as a tool to explain the clay morphology in a polymer matrix in a simple way.