Insulated electrical sleeves will melt at high temperature
As long as the temperature reaches the melting temperature of the casing material, it will melt. Iron can be turned into liquid. Can polymer plastics not melt? It's just how much this "high temperature" means.
Insulated electrical sleeves are divided into several materials, such as fiberglass insulated sleeves, PVC bushings, heat shrinkable sleeves, etc.. The temperature characteristics are different, such as the applicable temperature range of the heat shrinkable sleeve: -55 DEG C to 125 DEG C.
