PTFE, PFA, FEP, PVDF Fluoroplastic products industry experts
The basic characteristics and processing methods of PTFE
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2024-06-18
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Origin of 1. PTFE
The first PTFE sample in history was not consciously synthesized, but was inadvertently discovered and valued during the development of new fluorine-containing refrigerants using TFE as raw materials.
On April 6, 1938, Plunkett's assistant JackRebok found that there was no expected TFE outflow from the cylinder during the synthesis test with the stored TFE. What followed was a famous story and great discovery. When the valve is opened, the cylinder is inverted, and the metal wire is inserted into the inner wall of the cylinder, some white solid powder can be obtained, but its quality is less than the amount of TFE stored. The cylinder was cut open from the middle and more powder was found filling the bottom of the cylinder and the adjacent inner wall. This white powder was later confirmed to be PTFE.
Basic characteristics of 2. PTFE
Since all the hydrogen atoms connected to the main chain carbon atoms are replaced by fluorine atoms, polytetrafluoroethylene has many unique properties, and because of its high crystallinity and high viscosity even at the melting point, PTFE has unique physical and mechanical properties and processing properties, and because of its completely symmetrical molecular structure, PTFE has excellent electrical properties and good radiation resistance. In summary, the main features are as follows:
It has the lowest surface energy among all polymers, self-lubricating and non-sticky, and the surface of the product is not wetted;
It has the best chemical inertness, except for molten alkali metals and a few halogen fluorides, can resist almost all chemical substances;
It has excellent thermal stability, can be used for a long time at a high temperature of 260 ℃, and can adapt to low temperature environment;
④ It has good mechanical strength and low friction coefficient, but the product is prone to relaxation under stress;
⑤ has excellent dielectric properties, can be used as high-end electrical insulation materials;
It has good radiation resistance;
Not suitable for general plastics widely used thermoplastic processing methods, need to use special special processing methods;
The resulting unsintered film can be subjected to high-magnification stretching to produce a unique network structure microfiber porous material.
Processing method of 3. PTFE
PTFE is a non-melt processing fluororesin. Polytetrafluoroethylene (PTFE) is a homopolymer of TFE. According to different manufacturing methods, different product properties and different processing methods, it can be divided into the following main varieties.
(1) Suspension method PTFE resin PTFE
Suspension polytetrafluoroethylene resin is a granular resin obtained by suspension polymerization of TFE monomer in aqueous phase, which is made into multiple grades with different particle size and surface morphology after post-treatment (crushing, grinding, airflow crushing, granulation, pre-sintering, etc.). According to the different particle size, particle outer surface morphology and processing methods, it can be divided into several different grades: medium particle size resin, fine particle size resin, good fluidity resin (granulation resin, pre-sintered resin) and capacitor film special resin (made by low temperature polymerization).
(2) Dispersion method PTFE resin PTFE
The dispersion method polytetrafluoroethylene resin is a fine powder resin obtained by coagulating, washing and drying a PTFE emulsion obtained by emulsion polymerization of TFE monomer in an aqueous phase and in the presence of a surfactant (emulsifier).
According to the difference of processing methods applicable to the product, it is mainly divided into: medium and low compression ratio resin, high compression ratio resin, ultra-high molecular weight dispersed PTFE (suitable for processing fibers), compression ratio refers to the ratio of the cross-sectional area (or diameter) of the material cavity to the cross-sectional area (or diameter) of the die during paste extrusion.
(3)PTFEE concentrated dispersion
PTFE concentrated dispersion refers to the emulsion product with a concentration of 20% ~ 30% obtained by the same as TFE emulsion polymerization. After adding hydrocarbon emulsifier, the temperature is raised to a certain range, and then part of the water is removed or concentrated by other methods (such as raising the temperature under vacuum to remove part of the water), the emulsion product with a concentration of 50% ~ 60% is obtained. According to the purpose (through different polymerization process conditions to control the primary particle size is different, the average molecular weight is different, the amount of emulsifier added is different and adjust the concentrated emulsion viscosity is different) can be divided into coating grade, spinning grade, immersion grade.
This article is originally created by Teflon's little sister. Welcome to pay attention and take you to grow knowledge together!
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