Polytetrafluoroethylene (PTFE) is a high-performance polymer widely known for its remarkable chemical resistance, nonstick properties, and extreme temperature resistance. Herein, Alfa Chemistry takes you through the intricate details of PTFE manufacturing, from the synthesis of monomers to the production process of different forms of PTFE.
Industrial Synthesis of Tetrafluoroethylene
Tetrafluoroethylene is an important monomer raw material for the preparation of PTFE, and its synthesis process includes four steps as shown in the figure. Due to the presence of large quantities of corrosive acids (HCl and HF), the reactor must be made of highly corrosion-resistant materials such as platinum-lined nickel. Using a certain proportion of superheated steam as diluent can improve process efficiency.
PTFE Manufacturing
Polymerization is a critical step in PTFE manufacturing. TFE gas is introduced into a large autoclave reactor under carefully controlled conditions, such as temperature, pressure, and catalyst concentration. Frequently used catalysts include perfluoropropionic acid or radical initiators. In principle, tetrafluoroethylene can be polymerized in two different ways. Although both are high molecular weight PTFE polymers, the two products are distinctly different.
- PTFE Granular Resins
When little or no dispersant is used and the reaction mixture is vigorously stirred, the resulting precipitated polymer is often referred to as granular resin. - PTFE Fine Powder Resins
If the proper type and amount of dispersant are used and gentle agitation is maintained, the resulting product consists of small negatively charged oval colloidal particles (less than 0.5 μm in length). - PTFE Aqueous Dispersions
Aqueous dispersions can be used to produce fine powders or further concentrated into products for direct impregnation, coating, etc. 
Granular, fine powder, and dispersion PTFE products. [1]
- Filled PTFE Resins
To enhance the properties of the base polymer, such as wear resistance, creep resistance, and thermal and electrical conductivity, various fillers like glass fibers, powdered metals, and graphite can be mixed with above three PTFE polymers. The mixing process is typically done through intimate mixing. Aqueous dispersions can also be modified by introducing certain fillers, pigments, heat resistant dyes, carbon blacks, and powdered metals, particularly when used for film production. - PTFE Micro Powders
PTFE micro powders, also known as fluoroadditives, are PTFE homopolymer grades with a lower molecular weight compared to standard PTFE. They are manufactured through controlled suspension or dispersion polymerization processes, resulting in a lower molecular weight. Alternatively, they can be produced by degrading PTFE waste through thermal cracking (pyrolysis) or irradiation using high-energy electron beams (EB). These micro-powders are mainly used as additives in lubricants to improve their performance. They are also added to plastics and rubber to reduce friction coefficients, as well as printing inks and coatings to reduce their nonstick properties. - Modified PTFE
In order to overcome the limitations of traditional PTFE, namely poor creep resistance, difficult welding and high level of microporosity, some methods are used for modification. These property changes are achieved, for example, by adding small amounts of comonomers. The most common such modifier is perfluoropropyl vinyl ether (PPVE).
Reference
- Jiri George Drobny. Technology of Fluoropolymers, Second Edition.
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