Thermal Decomposition of Polymers （聚合物的热分解过程）.pdf

SECTION ONE CHAPTER 7 Thermal Decomposition of Polymers Craig L. Beyler and Marcelo M. Hirschler Introduction ical aspects of thermal decomposition of polymers. The chemical processes are responsible for the generation of Solid polymeric materials undergo both physical and flammable volatiles while physical changes, such as melt- chemical changes when heat is applied; this will usually ing and charring, can markedly alter the decomposition result in undesirable changes to the properties of the and burning characteristics of a material. material. A clear distinction needs to be made between The gasification of polymers is generally much more thermal decomposition and thermal degradation. The complicated than that of flammable liquids. For most American Society for Testing and Materials’ (ASTM) def- flammable liquids, the gasification process is simply evap- initions should provide helpful guidelines. Thermal de- oration. The liquid evaporates at a rate required to main- composition is “a process of extensive chemical species tain the equilibrium vapor pressure above the liquid. In change caused by heat.”1 Thermal degradation is “a the case of polymeric materials, the original material itself process whereby the action of heat or elevated tempera- is essentially involatile, and the quite large molecules ture on a material, product, or assembly causes a loss of