Jiangsu Aokai New Materials, a professional manufacturer of PTFE high-temperature cloth, provides a full introduction. The process of impregnating fiberglass fabric with PTFE dispersion is the core technology to evenly coat and sinter polytetrafluoroethylene onto fiberglass substrate, forming composite materials featuring high temperature resistance, electrical insulation and non-stick performance. Such products are widely applied in high-frequency copper-clad laminates, high-temperature non-stick conveyor belts, architectural membrane materials and other fields.
The complete basic process consists of seven key steps as follows:
This is the most critical pre-treatment step. A textile sizing agent (mainly paraffin wax, starch derivatives) is coated on fiberglass filaments during weaving; incomplete removal will severely impair interfacial bonding between PTFE and glass fibers.
· Main treatment method: The fabric continuously passes through a high-temperature furnace for thermal dewaxing at 350~400°C, fully oxidizing and decomposing all organic sizing agents.
· Follow-up handling: Dewaxed fabric is cooled down, sometimes rinsed with clean water or chemical solvents to eliminate residual ash, then dried to obtain clean blank white fabric ready for impregnation.
2. PTFE Emulsion Formulation
· Raw material: Concentrated PTFE dispersion with a standard solid content of approximately 60%.
· Mixing procedure: Dilute the stock dispersion with deionized water to a target concentration (40%–55%) based on required resin loading and impregnation viscosity. Appropriate surfactant is added to boost wetting performance on fiberglass; thickener may be incorporated to adjust viscosity when necessary.
3. Impregnation
The core target is full penetration of PTFE emulsion into fiber bundles and interstices of the woven fabric.
1. Dip-Squeeze Method (Most widely adopted): The fabric is guided through immersion rollers to fully soak in the emulsion tank, then passes through a pair of squeeze rollers. Coating weight is controlled by adjusting roller nip pressure to extrude excess emulsion and distribute resin uniformly.
2. Doctor Blade Coating: Emulsion is spread over the fabric surface via metal blades, suitable for high-viscosity dispersions.
4. Drying
Impregnated fabric enters a low-temperature drying oven operating at 100~150°C.
· Purpose: Gently evaporate water and partial surfactants, forming an even non-tacky dry film of PTFE particles on fiber surfaces.
· Temperature control note: Excessively high temperature will rapidly form a dense surface film, trapping internal moisture which vaporizes to create pinholes and blisters.
5. Sintering (Thermal Curing)
Dried fabric is immediately fed into a high-temperature sintering furnace for heat treatment at 360~390°C (up to 400°C for some grades).
· Mechanism: PTFE is a thermoplastic polymer. At temperatures far above its melting point (327°C), PTFE particles melt, flow and level out to form a continuous film, achieving mechanical interlocking and adhesion with fiberglass surfaces.
· Stage division: The sintering zone is divided into heating ramp, constant-temperature sintering and cooling segments to guarantee complete particle fusion without thermal degradation.
6. Multi-Cycle Impregnation & Sintering
A single impregnation-sintering cycle only generates an ultra-thin coating prone to pinhole defects. To reach target coating thickness and resin content (e.g., 45%–65% resin loading for high-frequency copper-clad laminate substrates), the full sequence of impregnation → drying → sintering is repeated 2 to 4 times or more. Each cycle further fills fiber gaps and increases coating thickness, eventually forming a pinhole-free dense composite sheet.
7. Post-Treatment & Winding
1. Surface modification: After the final sintering pass, corona treatment or chemical sodium-naphthalene etching can be applied to improve surface adhesion without damaging the substrate, facilitating subsequent copper cladding or secondary coating.
2. Edge trimming & winding: Fabric edges are trimmed straight, then the finished cloth is neatly wound by a take-up machine.
3. Quality inspection: Comprehensive testing of finished products including basis weight, thickness, tensile strength, peel strength, dielectric constant and visual surface defects.
Core Process Control Points
The critical parameters governing finished product quality are: complete desizing/dewaxing, full emulsion wetting, gradual low-temperature drying, precise sintering temperature setting, and consistent coating density after multiple impregnation cycles.
If you want to obtain detailed specifications, application scenarios and customized solutions for our full product portfolio including PTFE high-temperature cloth, PTFE high-temperature adhesive tape, PTFE high-temperature mesh belt, seamless heat press belt, single-sided PTFE fabric, high-temperature resistant conveyor belt and heat-resistant fiberglass cloth, please contact us via the information below:
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