The material of the boot will determine the temperature rating. TE Connectivity's elastomeric polymer -25 is rated to 150°C. Fluoropolymer -12 is rated to 200°C. The Zero-halogen -100 material used is rated to 105°C. The materials  when precoated with adhesive seal to IPE 67 levels and insulate to 600V. All materials are non-corrosive to copper.