Teflon film is made of molded sintered cylindrical blanks, which are cut into films by machine tools and then calendered. According to the different treatment methods, it can be divided into three kinds of oriented film, semi-oriented film and non-oriented film. At present, PTFE film products include porous film, microfiltration membrane, color film and so on.

1. PTFE color film

PTFE color film is suitable for electrical instruments or wire insulation marked by color. It is a new type of C- class insulation material with excellent comprehensive performance and is one of the indispensable important materials in the radio industry, aviation industry and cutting-edge science and technology. Polytetrafluoroethylene film generally adopts suspension polymerization polytetrafluoroethylene resin, and the particle diameter is required to be less than 150μm. The pigment must have good heat resistance (>400 ℃), fine particles, strong coloring force, and stable chemical reagents.

Its production process:

PTFE resin, pigment → mixing → compression molding → sintering → cooling → turning unoriented film → calendering semi-oriented film

Main process parameters:

Mixing: At present, there are two main mixing methods for producing color PTFE film: dry mixing and wet mixing. The research shows that the wet mixing method is more uniform than the dry mixing method, but the process is more, the cost is high, and the solvent needs to be added. In order to ensure the uniformity of the product, the wet mixing method is generally used.

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

Molding preforming: reasonable selection of preforming unit pressure is an important process condition for the production of PTFE color film. Mainly according to the fineness of the resin, compression ratio, pigment type fineness and other conditions to choose, generally in 20 ~ 40MPa.

Sintering cooling: Because the color film contains pigments, the thermal conductivity and thermal expansion coefficient are inconsistent with PTFE. Therefore, the temperature rise and fall in the sintering process is slower than that of ordinary PTFE film, the sintering temperature is lower than that of ordinary film, the temperature rise and fall is 20~30 ℃/h, and the sintering temperature is 375 ℃. The ordinary film heating rate at 327 degrees Celsius before 50~60 degrees Celsius/h, at 327 degrees Celsius after 30~40 degrees Celsius/h, sintering temperature of 380 degrees Celsius, cooling rate of 20~50 degrees Celsius/h.

Turning unoriented film: the tip angle of the knife should be 40 ° ~ 45 °, and the speed is slower than that of ordinary PTFE.

Calendered semi-oriented film: the calendering temperature varies with the thickness of the film, generally 5μm thick, 110 ℃ ± 5 ℃;30μm thick, 130 ℃ ± 10 ℃. Calendering multiple is 2.5~3.0.

Main equipment:

(1) Mixer;

(2) Hydraulic press 35 ~ 40MPa;

(3) Sintering furnace DL151;

(4) Precision CNC lathe C620;

(5) Roller of calender Φ100 × 120.

2. Polytetrafluoroethylene porous membrane

The porous PTFE membrane is a new type of air filter material. Air filters using this material are suitable for absorbing aerosols in the air or other gases in clean rooms used in the semiconductor industry with less pressure loss of the air and other gases.

In 1976, R.W.Gore first disclosed a process for producing a porous PTFE membrane of the trade name Groce-TexR. The powdered polytetrafluoroethylene and lubricant are mixed into a paste, extruded into a sheet, and after the lubricant is discharged to an elevated temperature (below the crystalline melting point), uniaxial or biaxial stretching is performed, and the length after stretching is more than 50 times the original length. The membrane has a nominal pore size of 0.02 μm to 10 μm and a thickness of 25 μm to 76 μm. Since 1977, Japanese researchers have published many patents, such as Japanese Patent Laid-Open Publication 16619/1988. Japanese Patent Publication 16019/1988. Japanese Patent Laid-Open No. 17216/1981 has made many studies on porous PTFE membranes for increasing porosity, decreasing pore size, reducing pressure loss, and the like. Recently, a membrane with an average pore diameter of 0.2μm ~ 0.5μm has been prepared by Honda Maru. When air passes through at a flow rate of 5.3 cm/s, the pressure loss is 10mm ~ 100mmH2O column. The porous PTFE membrane has a fibril to contact area ratio of 99 :1 to 75 :25, an average fibril diameter of 0.05μm ~ 0.2μm and a maximum contact area of not more than 2μm2. It is prepared by preparing an unsintered, unstretched PTFE film having a thickness of 100 μm from PTFE fine powder (from DaikinF104) (the film is disclosed in Japanese Patent Laid-Open No. 152825/1984). It was then heated in a furnace and held at 339°C for 50 seconds to obtain a continuous semi-sintered film of 0.50 degree of sintering. The film is then heated at an ambient temperature of 320°C for 15 minutes to simultaneously or continuously extend the film in both directions at a rate of 100 %/sec. The apparatus is manufactured by Iwamoto Corporation and has a draw ratio of 5 to 8 in the longitudinal direction and 15 to 25 in the width direction of the film. The total draw ratio was 75 to 200, and a PTFE porous film was obtained.