Effect of urea-containing anti-tracking additive on the tracking and erosion resistance of addition-cure liquid silicone rubber

Three novel urea-containing anti-tracking additives were prepared and used to enhance the tracking and erosion resistance of addition-cure liquid silicone rubber (ALSR). The suppression effect and mechanism of the additives on tracking and erosion were investigated by the inclined plane (IP) test, thermogravimetry (TG) and thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR). It was found that the anti-tracking additives not only significantly improved the tracking and erosion resistance but also enhanced the mechanical properties of the ALSR. When using 2 phr of the anti-tracking additive, all the ALSR samples could pass the 4.5 kV level in the IP test. This might be mainly attributed to the arc-quenching capability of the urea group and the formation of a ceramic barrier to protect the underlying materials from further degradation during the dry band arcing. The TG and TG-FTIR results revealed that the urea-containing anti-tracking additives could prevent the radical decomposition of the ALSR below 400 °C. Hence, it considerably improved the initial thermal degradation stability of the ALSR and prolonged the time to track.