(159ai) Application of Isoconversional Analysis to Understand the Mechanism of Degradation Inhibition in PVC/Coal Composites

Polymer degradation involves a complex array of reactions and is further complicated by the fact that many of these reactions take place in the condensed phase. In practice this means that the overall activation energy is a function of the activation energies for diffusion and for various reactions and so will change as degradation progresses and different reactions limit the degradation. Isoconversional analysis is capable of determining the overall activation energy as a function of conversion, which can give insight into which reactions are prevalent at any point in the reaction, and the effect that additives may have on these reactions. Inhibition of a reaction will be seen as an increase in activation energy, and catalysis will be seen as a decrease. When comparing a composite to virgin polymer, the overall activation energy can be higher at some conversions, but lower in others. These deviations can be correlated to which reactions are limiting at certain conversions to determine how additives interact with the degradation mechanism. The present study utilizes isoconversional analysis in this way to analyze the impact of the filler on thermal degradation in novel PVC/Coal composites. Results indicate that coal has the effect of increasing the overall activation energy, thereby inhibiting degradation.