Introduction of polytetrafluoroethylene film

PTFE film is made from molded and sintered cylindrical blanks, which are cut into film by machine tools and then calendered. According to the different processing methods, it can be divided into three kinds: directional film, semi-directional film and non-directional film, and the current PTFE film products include porous film, microfilm and color film.

1、Teflon color film

PTFE colored film is used in electrical instruments or wire insulation with color differentiation mark, it is a new type of C-level insulation material with excellent overall performance, and is one of the important materials indispensable in radio industry, aviation industry and cutting-edge science and technology. PTFE film generally uses suspension polymerization PTFE resin, requiring particle diameter of 150μm or less. The pigment must have good heat resistance (>400℃), fine particles, strong coloring power, stable to chemical reagents and other requirements.

The production process:

PTFE resin, pigment → mixing → molding → sintering → cooling → turning undirected film → calendering semi-directed film

Main process parameters:

Mixing: At present, there are two main ways to mix color PTFE films; dry mixing and wet mixing. Research shows that the wet mixing than dry mixing mixing uniform but more processes, high cost, the need to add solvent, in order to ensure the uniformity of the product is generally used wet mixing.

The process is PTFE resin, pigment and solvent → mixing → drying → solvent removal → color material.

Pre-molding: Reasonable choice of pre-molding unit pressure is an important process condition for producing PTFE color film. Mainly based on the resin fineness, compression ratio, pigment type fineness and other conditions to choose, generally in 20 ~ 40MPa.

Sintering and cooling: Because the color film contains pigments, the thermal conductivity and thermal expansion coefficient are not the same as PTFE. Therefore, in the sintering process, the temperature rise and fall is slower than that of ordinary PTFE films, and the sintering temperature is lower than that of ordinary films, with a rise and fall temperature of 20-30℃/h and a sintering temperature of 375 ℃. While the ordinary film temperature rise rate before 327 ℃ 50 ~ 60 ℃ / h, after 327 ℃ 30 ~ 40 ℃ / h, the sintering temperature of 380 ℃, the cooling rate of 20 ~ 50 ℃ / h.

Turning non-directional film: tool tip angle to 40 ° ~ 45 ° is appropriate, the speed is slower than the ordinary PTFE.

Calendering semi-directional film: calendering temperature varies with film thickness, generally 5μm thick, 110℃±5℃; 30μm thick, 130℃±10℃. Calendering multiplier is 2.5~3.0.

Main equipment:

(1) Mixer;

(2) Hydraulic press 35~40MPa;

(3) Sintering furnace DL151 ;

(4) Precision CNC lathe C620;

(5) Calendering machine with rollers Φ100 × 120.

2、Polytetrafluoroethylene porous membrane

PTFE porous membrane is a new type of air filtration material. The air filter with this material is suitable for absorbing suspended particles in the air or other gases in the clean room used in the semiconductor industry and the pressure loss of air and other gases is small.

In 1976, R.W. Gore first disclosed the manufacturing process of PTFE porous membranes under the trade name Groce-TexR. The powdered PTFE and lubricant are mixed into a paste, extruded into sheets, and then stretched uniaxially or biaxially at elevated temperatures (below the melting point of the crystals) after the lubricant is discharged, with the stretched length being more than 50 times the original length. In 1977, Japanese researchers have published many patents, such as Japanese Patent Publication 16619/1988, Japanese Patent Publication 16019/1988, Japanese Patent Publication 17216/1981 on porous PTFE film, increase the porosity, reduce the pore size, reduce the pressure Many researches have been done on porous PTFE membrane, increasing porosity, reducing pore size, reducing pressure loss, etc. Recently, Shinji Tamaru of Japan has produced a membrane with an average pore size of 0.2μm to 0.5μm and a pressure loss of 10mm to 100mm H2O column when air is passed at a flow rate of 5.3cm/s. The porous PTFE film has a filament-to-junction area ratio of 99:1 to 75:25, an average filament diameter of 0.05μm to 0.2μm and a maximum junction area of not more than 2μm2. The PTFE film was prepared by preparing a 100-μm-thick un-sintered, un-ductile PTFE film (disclosed in Japanese Patent Publication 152825/1984) from PTFE fine powder (made from DaikinF104). The film was then heated in a furnace and held at 339°C for 50 seconds to obtain a continuous semi-sintered film with a sintering degree of 0.50. The film is then heated at an ambient temperature of 320°C for 15 minutes to stretch the film simultaneously or continuously at a rate of 100 %/second in both directions. The equipment, manufactured by Iwamoto, has a stretching ratio of 5 to 8 in the longitudinal direction and 15 to 25 in the width direction, with a total stretching ratio of 75 to 200, resulting in porous PTFE films.

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