having more vinyl groups which could be favorable to form
a concentrated crosslinking network by the reaction with
PHMS. This network structure in ALSR can disperse the
stress to more molecular chains, thus improving the mechanical
properties [28,29].
3.2. Inclined plane testing
The tracking and erosion performance of the ALSR
samples in the IP test at 4.5 kV is shown in Fig. 3. As can be
seen, the ALSR without the anti-tracking additive failed the
IP test as three out of five samples failed due to excess
current, whereas the ALSR samples containing UPAS, IPUPAS
and DIPUPAS showed excellent tracking and erosion
performance with all the samples passing the IP test at
4.5 kV. These results showed that a small amount (2 phr) of
the urea-containing anti-tracking additives could effectively
improve the tracking and erosion resistance of the
ALSR, which could be ascribed to the ability of urea group to
quench electrical arcs during dry band arcing [18]. Due to
the heat generated from the dry band arcing, the ALSR
containing the anti-tracking additives could rapidly evolve