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Rhenotherm press info

Fluoroplastic Powder Coatings.

Applications, restrictions and improvements through the Rhenotherm "Jumbo" system.

Basics
The family of fluorine thermoplastics include:

  • PVDF
  • ECTFE
  • ETFE
  • PCTF
  • FEP
  • PFA

main application areas
Fluoroplastic coatings are predominantly used as cost-effective surface protection against chemical corrosion. In particular, where rubbers do not withstand the chemical and temperature-related influences or where linings are technically too difficult and / or too expensive.
Clear technical and economic advantages are offered by fluoroplastic coatings in difficult geometrical shapes. For example, in containers, lids with dished bottom and geometrically complicated nozzles, dip tubes and stirrers. But also in piping systems, bends, tees and valves.

previous limits
A fundamental problem inherent in the product of all plastics is the phenomenon of permeability and gas diffusion, i.e. the molecular penetration of liquids or gases. The quantity of both phenomena depends on the partial pressure of the liquid or gas. The partial pressure is in turn influenced by the temperature of the diffusing medium and the thickness of the coating. But also from the diffusion or permeation coefficient, which is a characteristic of the plastic that can hardly be influenced.
However, one can influence the layer thickness as a characteristic. For example, the layer thickness of PTFE linings from the original 2-3 mm has been increased to 4-6 mm.
In contrast, all conventional powder coatings are limited in their layer thickness, as these materials - as the name suggests - are applied in powder form and fused. In the rarest of cases, this is done in a single application, but usually through multiple applications. The following applies: the thicker the desired layer, the more jobs.
From a layer cover of approx. 1000µ, the physics can no longer be undermined. This means that the material begins to flow off at the edges when it is sintered (fusing). This effect can be avoided by using technical tricks, but it cannot be completely prevented. This leaves the “old weak point” of the limited layer thickness of approx. 1000µ and, as a consequence, the susceptibility to permeation, diffusion and mechanical damage already cited.
The solution to the problem with RHENOGUARD® "Jumbo".
The RHENOGUARD® "Jumbo" system is a patent pending process for fluoroplastic coatings developed by Rhenotherm GmbH, the thickness of which largely eliminates the risk of permeation and vapor diffusion. To be more precise: For the first time, a fluoroplastic coating has the dimensions of a lining.
This process is characterized by a sandwich-like structure of two or more plastic layers with different flow behavior. It is built up in two "layers" at least twice the thickness, which means that at least twice the security is achieved.
During the application you can check the condition of the respective plastic layer (eg layer thickness) so that you can proceed very specifically and - if necessary - corrective when applying the next one.
The greatest risk of runoff is at the edges. They should have a minimum radius of 5mm to build a solid layer. In practice, however, for structural reasons, you will mostly have to be content with only 3 mm. In these cases, applying different "layers" increases the radius and thus supports the formation of a thick layer.
With geometrically difficult objects (e.g. many edges, but above all different base material thicknesses), layer thicknesses of 8 mm can be achieved with RHENOGUARD2 "Jumbo". For parts with a simple geometry and uniform material thickness, it is even 3-5 mm!

RHENOGUARD “Jumbo” is available in two system variants with different base resin combinations.
"Jumbo I": Layer thicknesses up to 5 mm. Experience has shown that use in chemical processes up to 100 ° C is usually problem-free. Temperatures up to 130 ° C must be tested on a case-by-case basis. This system shows its limits at higher temperatures and with strongly oxidizing acids.

"Jumbo II": Layer thicknesses up to approx. 2 mm. This system is based on fully fluorinated plastics such as PFA, PTFE and FEP. Consequently, the use in chemical applications corresponds to that of fully fluorinated plastics. This means that application temperatures in chemical applications of 150 ° C are possible. Temperatures up to 180 ° C must be tested for the respective application. In this context, clarity should be provided with regard to the permanent use temperatures of fluoroplastics: By definition (see DU PONT, Hoechst and Allied Chemical) the raw material manufacturers define the permanent use temperature as the temperature at which the plastic still has 50% of its physical values. These values ​​are meaningless as a reference value for the chemical use of fluoroplastic coatings. All the more so since they only refer to the raw plastic and use tests are only aimed at the specific use as cable insulation.

Thick film - coatings versus linings?
Coatings such as the "Jumbo systems are not to be understood as a fundamental replacement for linings, but as a complementary technique. Because they complement an offer where linings are no longer economically vetretbar.

From this point of view, a thick-film coating of the RHENOGUARD® “Jumbo” caliber is definitely an alternative to competition - especially for lining companies that want to offer their customers the most economical process technologies.

Fig. RHENOGUARD “Jumbo” multi-layer system structure approx. 3 mm