How Do PTFE and Glass Fiber Bond Without Delamination Without Chemical Bonds?

Jiangsu Aokai New Materials, a leading manufacturer of PTFE high-temperature fabrics, explains:

Polytetrafluoroethylene (PTFE) and glass fiber (mainly composed of silica) cannot form chemical bonds. PTFE has an extremely low surface energy (approximately 18 mN/m), known as a "non-stick coating", while glass fiber is a hydrophilic polar inorganic material. The two are inherently incompatible.

At Aokai, we impregnate glass fiber cloth with PTFE emulsion, mainly through the following methods:Although PTFE itself is difficult to bond, a coupling agent (such as silane) can be used to build a bridge on the glass fiber surface. The principle is:Glass fiber surface is coated with a silane coupling agent. One end of the silane (alkoxy group) undergoes a condensation reaction with silanol groups (Si-OH) on the glass fiber to form chemical bonds; the other end (such as amino group, epoxy group) is reactive.

If PTFE itself is untreated, the reactive end of the coupling agent cannot bond with PTFE, so surface treatment is required. A common practice is to add coupling agents and polymer binders (such as PFA, FEP — perfluoroalkoxy resin or tetrafluoroethylene-hexafluoropropylene copolymer, which are melt-processable fluoroplastics) into the PTFE emulsion.

Transition layer: Perfluoroalkoxy resin or tetrafluoroethylene-hexafluoropropylene copolymer is used as an intermediate layer. These fluoroplastics have good chemical compatibility with PTFE, can melt and flow at a lower temperature, bond the silane-treated glass fiber with the bulk PTFE, form a gradient interface, and eliminate stress mutation.

The bonding between PTFE and glass fiber is essentially a physical combination of mechanical interlocking + stress compression + gradient transition layer.

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

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