Highly Efficient Pyrolysis of Waste High-Temperature Vulcanized Silicone Rubber Assisted by Mechanochemical Milling

High-temperature vulcanized silicone rubber (HTV SIR) possesses great chemical resistance and high thermal stability, but these excellent performances also impede its recycling. In this respect, the waste HTV SIR from retired composite insulators with/without the KOH catalyst was ground by solid-state shear milling (S3M). The morphology and structure of silicone rubber powder were analyzed, and the pyrolysis behaviors of the obtained silicone rubber powders were revealed by thermogravimetry (TG) and pyrolysis gas-phase/mass spectrometry (Py-GC/MS). The results show that the mechanochemical milling via S3M could significantly reduce the particle size of silicone rubber and destroy the cross-linking structure of the waste HTV SIR, thus leading to an obvious improvement in the sol fraction. The maximum weight loss rate temperature of waste HTV SIR with the KOH catalyst assisted by mechanochemical milling was 150 °C lower than those without milling. Moreover, a greatly reduced catalytic pyrolysis duration along with more concentrated pyrolysis products at 400 °C was achieved after grinding three times. At last, the pyrolysis mechanism of the waste HTV SIR assisted by mechanochemical milling is proposed. These obtained results provide a great potential for large-scale recycling of waste silicone rubber with stable structure and complex components.