Investigation of the Properties of Gap‐Filling Materials Enhanced With Nanofillers

The performance of gap‐filling materials, a key part of valve hall sealing, directly impacted the system’s overall firestopping effect. In this study, nanofillers were used to modify the gap‐filling materials. The effects of nanofiller modification on the performance of the gap‐filling materials were investigated through thermogravimetric analysis (TGA), oxygen index (OI) test, vertical burning test, cone calorimetry, muffle furnace calcination, and tensile strength test. The TGA results showed that using carbon nanotubes (CNTs) as nanofillers increased the initial decomposition temperature of the gap‐filling material to 463.7 °C, with a residual char yield of 77.2% at 800 °C, significantly enhancing its thermal stability. Muffle furnace calcination images demonstrated that the nanofillers effectively improved the ceramic‐forming properties of the gap‐filling material. The OI increased to 37.1%, and the material achieved a V‐0 rating in the vertical burning test. The peak heat release rate (pHRR) and total heat release (THR) were reduced to 65.1 kW/m 2 and 38.2 MJ/m 2 , respectively, representing decreases of 57.8% and 49.2% compared to the unmodified gap‐filling material. Additionally, the fire growth index (FGI) decreased, while the fire performance index (FPI) improved. These results indicated that nanofillers can significantly enhance the flame retardancy and intrinsic safety of gap‐filling materials, thereby ensuring the safe operation of ultrahigh voltage (UHV) transmission lines and supporting the global advancement of UHV technology.