Some basic aspects of flame resistance of polymeric materials

For a better insight into flame resistance and flame extinction it is useful to split the combustion process into its constituent elements. It then appears that the thermal decomposition is the first link in a series of reactions and therefore a better understanding of this decomposition is a prerequisite. Further, it is found that the amount of char and the amount of incombustible gases that may be formed in thermal decomposition are very important quantitative measures of flame resistance. For a large number of model substances the char residue upon pyrolysis has been determined. The residue is found to be very clearly related to the chemical structure of the polymer, so much so that the amount of char can be predicted from the structure. Finally, it has been demonstrated that there is a very significant relation between the pyrolysis residue (%) and the (limiting) oxygen index.