Which wire insulation type is generally considered heat resistant?

Asbestos is known for its remarkable heat resistance properties, which is why it has been used historically in various applications that require protection from high temperatures, such as insulation for electrical wires and fireproofing materials. This characteristic makes it suitable for environments where high heat exposure is a concern, allowing it to maintain its structural integrity and insulative properties under such conditions.

While other materials like thermoplastic, rubber, and varnished cambric may offer some degree of heat resistance, they are not as effective as asbestos in extreme heat scenarios. Thermoplastic insulation can deform or melt at high temperatures, rubber can degrade and lose its flexibility, and varnished cambric, though better than some, doesn't match the extreme heat resistance that asbestos provides.