Effect of bis-TEMPO Sebacate on Mechanical Properties and Oxidative Resistance of Peroxide-Crosslinked Polyolefin Compositions

TEMPO derivatives are well known as scorch retardants due to their ability to effectively quench free alkyl radicals during peroxide crosslinking of polymer compositions. However, in practice this leads to the loss of crosslinking density due to a irreversible decrease in the number of alkyl radicals involved in the crosslinking process. One approach to solving this problem is the use of TEMPO-based biradical molecules, which, on the one hand, are able to effectively quench alkyl radicals, and on the other hand, can couple macroradicals, partially compensating for the loss of crosslinking density. The aim of this work was to reveal the effect of bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate (bis-TEMPO) in the concentration range of 0.11-0.44 phr on the delay in the onset of dynamic crosslinking of polyolefin composites initiated by peroxide, as well as the oxidative stability of the resulting crosslinked composites. The obtained data show that using bis-TEMPO at a concentration of less than 0.27 phr increases the crosslinking density of the polyolefin composite, with a crosslinking onset delay of up to 36 s achieved. Simultaneously, antioxidant functionality of bis-TEMPO in crosslinked composites is considered moderate and leads to an increase in the OIT values by 1.7-2.8 times. The crosslinking onset delay time under dynamic conditions is well described by a first-order kinetic model at a constant temperature. The obtained data confirm the efficiency and predictability of bis-TEMPO as a scorch retardant for polyolefin composites.