Why is Glass Fiber Cloth Subject to Dewaxing Before Impregnation with PTFE Emulsion? What is the Principle?

As a professional manufacturer of PTFE high-temperature fabrics, Aokai New Materials conducts high-temperature treatment on glass fiber cloth. Before impregnation with PTFE (Polytetrafluoroethylene) emulsion, the glass fiber cloth undergoes dewaxing and degumming to remove sizing agents (textile auxiliaries) on the fiber surface. These auxiliaries serve for bundling, lubrication and protection during fiber drawing and weaving. However, if not removed, they will severely compromise the composite quality of PTFE and glass fiber. The principles are mainly as follows:

1. Remove Low Surface Energy Substances and Improve Wettability

Paraffin, lubricating oil and other components in sizing agents are low surface energy substances. If retained, the PTFE emulsion (with low surface tension but strict requirements) cannot spread evenly on the glass fiber surface, resulting in defects such as craters and fish eyes. Through high-temperature thermal cleaning or solvent cleaning, contaminants are removed and the surface energy of glass fiber is increased, enabling full wetting by PTFE.

2. Prevent Carbonization and Delamination During High-Temperature Sintering

The sintering temperature of PTFE is as high as 360–380°C. Residual paraffin or epoxy adhesives on the glass fiber surface will carbonize at such high temperatures, producing black particles or gas. This not only pollutes the medium (affecting dielectric properties in high-frequency copper-clad laminates) but, more critically, the carbonized layer forms a weak interface, drastically reducing the bonding strength between PTFE and glass fiber and causing delamination of the composite material.

3. Establish a Strong "Mechanical Anchoring" Effect

High-quality dewaxing and degumming (especially high-temperature heat treatment) is more than just "cleaning". As organic matter is removed, the glass fiber surface is slightly etched to form micropores or expose more silanol groups (-OH). This creates conditions for subsequent coupling agent coating (e.g., phenyl silane), allowing PTFE to form chemical bonds or physical anchoring points with glass fiber via coupling agents — transforming simple "coating" into firm "bonding".

4. Avoid Deterioration of Interfacial Dielectric Properties

In high-end applications such as high-frequency and high-speed copper-clad laminates, residual polar organic substances (wax, gum) significantly increase dielectric loss under high temperature and high frequency. Dewaxing and degumming ensures the glass fiber-PTFE composite maintains extremely low dielectric constant and dielectric loss.

In summary, the core purpose of this treatment is to eliminate weak interface layers and ensure that PTFE, a low surface energy material, achieves perfect wetting and high-strength bonding on clean, high-surface-energy glass fiber.

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

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