Determination of the degradation mechanism from the kinetic parameters of dehydrochlorinated poly(vinyl chloride) decomposition

Kinetic theory in regards to the basic understanding of reaction order as it relates to polymer degradation is discussed. This new theory is then tested by determining the kinetic parameters for dehydrochlorinated poly(vinyl chloride) using thermogravimetric analysis. Four different mechanisms of degradation were deduced from four sets of kinetic parameters. The calculated kinetic parameters were apparent reaction order, apparent activation energy, and apparent frequency factor as determined by the original Freeman and Carroll model. The four regions/mechanisms attained by the theory from the data are in order of appearance: final dehydrochlorination: random chain scission: cyclization; coke degradation. The data indicate transition regions between the individual regions where two mechanisms are competing with one another. Also, a method for obtaining the optimal heating rate from a set of heating rates is discussed.