FEP, the full name of fluorinated ethylene propylene, translated into ethylene fluorinated propylene copolymer (perfluoroethylene copolymer) English name: Teflon FEP, is a class of chemicals. FEP is a mixture of tetrafluoroethylene and hexafluoropropylene. FEP crystals melt at 304°C and have a density of 2.15g/CC (g/cm3). Compared with many engineering plastics, FEP is suitable for soft plastics and has lower tensile strength, wear resistance and creep resistance.
YOZONETECH as the source manufacturer, their engineers said that FEP has better processing performance. The insulation of wires and cables can be covered by the usual extrusion method. The following are the things that need to be prepared for the FEP tube before extrusion:
1) Feeding: Before FEP extrusion, pre-baking at 120°C for about 3 hours is appropriate.
2) Conductive core wire preheating: In order to ensure the same temperature inside and outside the extruded FEP insulation, the conductive core wire should be preheated to 300-350℃.
3) The temperature distribution of the extruder: The temperature distribution of the extruder is generally consistent with the temperature distribution when the temperature rises linearly from 280°C (feeding port) to 380°C (head);
4) The stretch ratio of the die sleeve: should be selected in the range of 50-200.
5) Screw speed: After the screw speed is adjusted with the temperature, it does not change frequently during the FEP resin extrusion process, and can be adjusted slightly if necessary.
6) Mold heat preservation: The mold heat preservation area should cover the entire stretching area, and the heat preservation temperature should be 350-380℃ to avoid the sudden cold stress on the surface when the FEP cone is formed, which will cause the heat preservation to crack.
7) Cooling of insulated wires: water cooling after the wires are extruded from the extruder. The distance between the mold mouth and the water tank is suitable to be relatively close, and it is recommended that it be no more than 20cm.
FEP resin exists in the form of a product before processing and molding:
1. Granules, used for extrusion molding and injection molding;
2. Disperse, used for dipping and coating;
3. Powder, used for electric deviation correction spraying.
Below we mainly understand several molding processing methods of FEP.
1. Melt extrusion molding
2. Forming: heating, pressurizing and plasticizing;
3. Blow molding
4. Vacuum forming
6. Coating treatment
7. Static spray
The extrusion quality of FEP hose is also related to the following related parameters. One factor may cause the quality of FEP hose extrusion to be different from ideal.
Extrusion molding temperature includes barrel temperature, plastic temperature, screw temperature, generally we measure barrel temperature. Temperature controlled heating and cooling system, due to the spiral structure, unstable heating and cooling system, screw speed changes and other reasons, the radial and axial temperature fluctuations of the extruded material affect the quality of the product, and the product strength is different, resulting in residual Stress, the surface is gray and shiny. In order to ensure the quality of the product, the temperature must be stable.
Due to the structure of the screw and barrel, the filter head, filter, and filter plate have resistance, which makes the plastic internal pressure. As shown in the figure, the pressure changes and the pressure fluctuates.
3. Extrusion speed
The mass or length of plastic extruded per unit time. Factors affecting the extrusion rate: head resistance, screw and barrel structure, screw speed, heating, cooling system, plastic characteristics. However, when the product is set, the extrusion rate is only related to the screw speed. The extrusion rate will also fluctuate, affecting the geometry and size of the product.
Temperature, pressure, and extrusion rate all fluctuate. In order to ensure product quality, YOZONETECH reminds everyone as the source manufacturer: The screw should be designed reasonably, the heating and cooling system and the screw speed should be controlled to stabilize the screw speed to reduce parameter fluctuations.