Why Does PTFE High-Temperature Cloth Become Hard and Brittle After Long-Term Use at High Temperatures?

Jiangsu Aokai New Materials, a source manufacturer of PTFE high-temperature cloth, explains the hardening and embrittlement of PTFE high-temperature cloth after prolonged high-temperature service from three perspectives: polymer chain relaxation, cross-linking, and degradation. It should be noted that the core material of PTFE high-temperature cloth is polytetrafluoroethylene (PTFE), and the following analysis focuses on the microstructural changes of PTFE high-temperature cloth.

I. Molecular Chain Relaxation (Physical Aging)

At high temperatures, the mobility of molecular chains in the amorphous regions of PTFE high-temperature cloth increases, and they gradually transform into a more ordered crystalline state, resulting in higher crystallinity. This chain relaxation process reduces the mobility of molecular segments in PTFE high-temperature cloth, which macroscopically manifests as the material changing from flexible to hard and brittle.

II. Cross-Linking Reaction

When PTFE high-temperature cloth is exposed to high temperatures for a long time (especially near or exceeding its upper service limit), in the presence of trace oxygen or radiation, PTFE molecules lose fluorine atoms to form free radicals, which then trigger intermolecular cross-linking. The cross-linked network directly restricts the relative sliding of molecular chains in PTFE high-temperature cloth, causing it to lose flexibility. This is one of the key chemical reasons for the hardening and embrittlement of PTFE high-temperature cloth.

III. Degradation Reaction

At higher temperatures or in the presence of oxygen, the main chains of PTFE high-temperature cloth break and degrade, producing low-molecular-weight fragments and releasing fluoride gases. Although the material may soften initially, continuous degradation leads to a sharp drop in molecular weight and damage to the original crystalline structure. Eventually, the surface of PTFE high-temperature cloth powders, cracks, and shows irreversible embrittlement.

Summary: When PTFE high-temperature cloth is heated for a long time, chain relaxation (crystallization) and cross-linking together cause hardening and loss of toughness; under harsh conditions, degradation further destroys structural integrity. The combination of these three factors ultimately makes PTFE high-temperature cloth hard and brittle.

The above information is provided by Jiangsu Aokai New Materials Technology Co., Ltd.

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