Brief introduction of polytetrafluoroethylene (PTFE) material properties
This material is particularly important in cable applications. Most of the wrapping cable insulation materials use PTFE, why always choose this material? The following is known by understanding the performance of this material.
1. PTFE overview
Polytetrafluoroethylene is abbreviated as F-4, which is an engineering material. It has the characteristics of various other engineering plastics, and its excellent performance is unmatched by other engineering plastics; its wide frequency range and high and low temperature use Scope, excellent chemical stability, high electrical insulation, outstanding surface non-stickiness, good lubrication and resistance to atmospheric aging, make PTFE superior to other plastics in the relevant technologies for solving various sectors of the industry.
2. Types and uses of PTFE
(1) According to different polymerization methods, polytetrafluoroethylene is divided into two categories: suspended polytetrafluoroethylene and dispersed polytetrafluoroethylene.
(2) Suspended polytetrafluoroethylene resin is a white powder with large particles. After proper post-treatment, powders with different particle sizes can be obtained. This powdered resin is used for molding, calendering and forming, not directly used in the production of wires and cables. When used for wire and cable insulation, the suspension PTFE should be molded, sintered into a cylindrical blank, and then turned into a PTFE film on a lathe. This kind of film is also called clinker tape, which is used for wrapping and insulating power supply cables.
(3) Dispersed PTFE is divided into two types: powder and concentrated dispersion. Among them: the powder dispersion resin is mixed with a certain amount of additives (such as petroleum ether) and fillers (such as quartz powder), and then is specially used for pressing and molding. It is suitable for pressing and processing of thin-walled products such as wires and cables. There are many applications in wire production: the powdery dispersed resin can also be pressed into a shape, and then rolled into a film (also known as a raw material tape) for thin-diameter wire insulation or wire sheath wrapping. Polytetrafluoroethylene concentrated dispersion is mainly used for impregnating porous materials (such as asbestos, glass, fiber weaving) and surface coating of metal bearings made by powder metallurgy. The glass fiber braid of PTFE insulated magnet wire and high temperature resistant wire is coated with PTFE concentrate.
3. The structural characteristics of PTFE
The above picture shows the molecular structure of PTFE. Polytetrafluoroethylene is polymerized by tetrafluoroethylene. The unbranched linear polymer with completely symmetrical molecular structure, with a density of (2.280～2.295) g/cm³ and a crystallinity of 93%～98%, is almost a completely crystalline polymer.
Among the known polymer bonds, the C-F bond is one of the strongest bonds. The main carbon bond of the macromolecule is tightly guarded by fluorine atoms, so that the C-C bond is not attacked by ordinary active molecules. In addition, the fluorine atoms are relatively bulky and mutually repel each other. The entire macromolecular chain is helical, and there are symmetrical fluorine atoms on the main chain of the macromolecule, so it is electrically neutralized and the entire molecule is non-polar. The particularity of this structure makes PTFE have excellent heat resistance, chemical resistance and solvent resistance stability, high electrical insulation, surface non-stickiness, and lubricity, etc., and has a very high melt viscosity .