What Are the Processing Elements of ePTFE?

Since the preparation of EPTFE sealing tape adopts the method of stretching and expansion, the cross section of the finished product will naturally form a shape that tends to be round, ellipse or similar polygonal with arc transition due to the influence of the pull force of the finished product under natural conditions. These shapes are difficult to fit and fill the sealing groove perfectly. In particular, the product's low strength, poor density uniformity, anisotropy and poor pressure resistance directly affect the sealing performance of the product.

 

When installing ePTFE gasket tape, many manufacturers did not expect its unique and complicated manufacturing process at all. It is understood that ePTFE-related products have their own unique characteristics, such products include expanded PTFE sealing tape, expanded PTFE membrane, expanded PTFE cable wrapping tape and so on. This article mainly introduces the main points of the complexity and engineering technology involved in the development and manufacturing of ePTFE-related products.

 

The existing EPTFE sealing tape has poor sealing performance. How to provide a method for preparing high-strength EPTFE sealing tape that can produce EPTFE sealing tape with high strength, uniform density, excellent anisotropy, and the cross-sectional shape and the sealing groove perfectly fit?

 

1. Resin. Resin grade is very important for making high-quality ePTFE cable wrapping tape. The resin must be a fine powder that can withstand a good extrusion load. Certain characteristics of the resin must be within the specified range, otherwise the powder will not work.

 

The solvent oil mixed solution with a mass fraction of 20-30% and the polytetrafluoroethylene dispersed resin powder are uniformly mixed, pre-pressed into a columnar blank, and extruded through a die. The extrusion compression ratio is 50-120. Then, it is rolled on the rolling drum into a PTFE tape with a width of 200-350mm and a thickness of 0.2-0.3mm.

 

2. Mix. Mix the resin with the extrusion aid. After completion, the resin is extruded into the desired contour. The mixing time and the amount of extrusion aid are very important.

 

3. Extrusion. This process needs to be carried out at a steady speed and under a certain pressure. The extrusion pressure must be within an acceptable range. If the pressure is too low, the extrudate is weak and may break during stretching. Conversely, the extrudate is difficult to stretch.

 

4. Dry. The purpose of this process is to remove naphtha from the material. Since the material will be heated to high temperature very quickly, all traces of naphtha must be removed due to safety considerations.

 

5. Stretching. The stretching process involves three sub-parameters, namely temperature, stretching ratio and speed.

 

The colorful PTFE tape is stretched longitudinally and transversely through a stretching oven. Longitudinal stretching is divided into two stages: degreasing and stretching. The stretching ratio is 8-15 times, and the stretching rate is 400-600%/sec. Transverse stretching is divided into three stages: preheating, stretching and shaping. The stretching ratio is 8-12 times, the running speed is 4-10m/min, and the biaxially stretched film is prepared.

 

6. Final curing. Expanded PTFE tape, especially high-speed stretch PTFE tape, will try to pull back on itself. This leads to shortened length and increased density. Therefore, it is necessary to combine special winding technology to ensure that the material maintains its characteristics.