Selectivity of shear flow on chains for the degradation reaction of melt polyolefin elastomer with dicumyl peroxide.

The degrading behaviors of three kinds of melt polyolefin elastomers (POEs) at presence of dicumyl peroxides (DCPs) in transient shear flow were evaluated at elevated temperature by parallel plate rheometer. The critical shear rates for degradations of all POEs were different from one to another. The rheological and gel permeation chromatograph (GPC) results showed that the degradation was more and more distinct and the duration to achieve one similar level of molecular weight decreased as the shear rate increased. For quantitative information on chain structure, linear viscoelasticity combined with branch-on-branch (BOB) dynamic model was used to predict probable compositions and chain topologies of the modified products, which were reasonably explained by the suggested mechanism of radical reactions and could confirm that there was a kind of selectivity of shear rate on POE chains for degradation. Higher shear rate can enlarge the differences in mobility of the two scission parts and can further increase the possibility of effective degradation on the original chains. [ABSTRACT FROM AUTHOR]