Production Technology of PTFE Membrane Structural Materials

The concentration of dispersion directly affects the thickness, surface finish, resin content and flatness of the film. The higher the concentration, the greater the amount of each coating, the greater the thickness of the resin, but each impregnation thickness can not be too large, too large is prone to crack after sintering, affecting product quality.

 

Too small can not meet the thickness and content requirements of the resin, and then affect the appearance and mechanical properties of the product. In general, the concentration of PTFE dispersion increases gradually during multiple impregnations.

In the industrial production of PTFE film, the drying temperature, baking temperature and sintering temperature are continuous and gradual, from low temperature to high temperature.

 

 

The purpose of drying is to remove moisture and low boiling point volatiles from the dispersion. The temperature is too low, the water removal is not complete, affecting the next baking effect: the temperature is too high, which is not conducive to the uniform escape of water, and may also produce flow marks or bubbles, affecting the appearance of the product. With reference to relevant data and experiments, the drying temperature is generally selected at 100~150 ℃.

 

 

Baking is to remove residual moisture, surfactants and low molecular substances in the resin. The temperature is too low, which may make the cloth sticky due to incomplete drying of the resin.

 

In high temperature sintering, excessive residual organic matter carbonization and yellowing affect the appearance of the product, and will affect the lower dipping; Excessive temperature may cause local resin plasticization, resulting in uneven coating thickness and insufficient softness of the film.

 

Considering the boiling point of organic matter and the melting point of resin (327 ° C), the baking temperature is generally selected at 280~290 ° C.

 

 

The high temperature in the sintering area melts the resin, eliminates the interface, and makes it better bonded with the glass fiber cloth, thus plasticizing the film material. The sintering quality of the product directly affects the mechanical properties and appearance of the film.

 

The temperature is too low, the plasticization temperature of the resin cannot be reached, the product is difficult to form, and the resin and the substrate cannot be fully combined.

 

If the temperature is too high, the polymerization degree of PTFE will be greatly reduced, and the surface color of the film will be deepened and the texture will be hard.

 

Considering various factors, the general sintering temperature is selected at 360~390 ℃.

 

Generally, in industrial continuous production, the machine running speed is mainly adjusted by controlling the sintering time. Sintering time is too short, will make the front immersion, drying, baking and other processes can not meet the treatment requirements, is not conducive to the base cloth and resin bonding, and then affect the appearance and quality of the product; Sintering time is too long, on the one hand will make the film brittle and hard, the surface color may turn black, performance decline, on the other hand also reduces the production efficiency.

 

Therefore, the sintering time is generally controlled at 30~90s

 

The heat treatment of the glass fiber base cloth is to remove the wetting agent on the glass fiber surface, and the coating of the wetting agent can enhance the wear resistance and workability of the glass fiber.

 

Generally, heat treatment method is used, which is divided into high temperature heat treatment (500~650℃) and medium and low temperature heat treatment (300~450℃).

The higher the heat treatment temperature and time, the higher the removal rate of the wetting agent, but the greater the decrease of the strength of the glass fiber. PTFE film has high strength requirements and requires small strength loss after heat treatment, so medium and low temperature heat treatment is generally used.