Parameters affecting process efficiency of peroxide‐initiated controlled degradation of polypropylene

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Abstract
Parameters affecting the process efficiency of the peroxide‐initiated controlled degradation of polypropylene, such as concentration of peroxide, reaction temperature, and reaction time, are investigated under in situ uniform, microsegregation, and macrosegregation conditions. Reactions were carried out under static (no mixing) and dynamic conditions on model samples and samples processed in batch mixers, respectively. As expected, MW and MWD decrease with increasing peroxide concentration. Low‐ and mid‐MW fractions increase at the expense of the high‐MW fractions. Localization of peroxide occurs under macrosegregation conditions and causes overall loss of peroxide efficiency and side reactions. MW and MWD undergo no further change after three to four times the half‐life of the peroxide. A kinetic model developed using the quasisteady‐state approximation on free radicals successfully simulates the degradation reaction kinetics for peroxide uniformly mixed. The method of moments is used to calculate the molecular weight averages. The results of this work confirm the importance of mixing uniformity as a parameter controlling the product characteristics in reactive processing.