Schlauch aus PTFE für die industrielle Produktion

1. The material PTFE

The four letters PTFE stand for polytetrafluoroethylene, which was originally also known under the trade name "Teflon" from the DuPont company. PTFE is a partially crystalline polymer of fluorine and carbon. PTFE was discovered in 1938 by chemist Roy Plunkett when he experimented with tetrafluoroethylene (TFE) and converted it to "colorless crumbs" polymerized. In the meantime, PTFE has become indispensable in many applications because of its outstanding properties:

PTFE is very inert and therefore has a very high resistance to almost all bases, alcohols, benzines, oils.
PTFE has a very low coefficient of friction and is therefore an ideal lubricant.
PTFE has an extremely low surface tension, so it is almost impossible to wet. There are almost no materials that stick to PTFE - also known as the non-stick effect of PTFE.
PTFE has a high temperature resistance up to +260 °C.
PTFE has very low electrical conductivity and therefore good insulation properties.

PTFE has clear advantages over almost all other plastics and is the best technical solution for many applications.

PTFE comes in two types:

Non-modified PTFE (non modified)
Modifi ziertes PTFE (modifi ed)

Beim modifi zierten PTFE wird Perfl uoroPropylVinylEther (PPVE) zugesetzt. Hierdurch werden die Eigenschaften wie z. B. geringere Deformation, geringere Porosität, höhere Reißdehnung sowie geringere Permeation verbessert. Markert verwendet in der Herstellung ausschließlich modifi ziertes PTFE.

2. The production of PTFE hoses

Polymerization produces a white PTFE powder. This produces the raw material for the manufacture of PTFE products. Market leaders in the production of PTFE include DuPont (now Chemours), DOW (3M™ Dyneon™) and Daikin.

The PTFE powder is mixed with a binder (e.g. ISOPAR) for further processing and thus becomes processable. In the production of PTFE hoses, the resulting emulsion is thermally heated in an extruder and pressed over a die. If the PTFE is to be conductive, carbon is added to the PTFE in the mixing process (this is the starting material for the so-called "black" PTFE). By means of extrusion, the PTFE emulsion is sintered to the desired shape. In the final cooling and cutting process, the final PTFE hose liner is produced.

The extrusion process is extremely complex, as only balanced tempering phases can ensure complete polymerization of the PTFE powder. Furthermore, the die and the PTFE guide must be matched to each other with high precision; only in this way PTFE liners can be produced reliable. The smallest inclusions or tolerance deviations in the PTFE liner can drastically influence the strength.

Only raw materials of the highest quality may be used for industrial hose lines. Therefore, only the PTFE compound Teflon T-62 (Chemours formerly Dupont) is used for hoses.

3. PTFE coextruded

4. PTFE in comparison

5. Requirement for PTFE

5.1 FDA approval

The FDA is the U.S. Food and Drug Administration, the government agency responsible for monitoring all goods marketed in the United States. This also includes all imports, which is why the guidelines and regulations of the US authority are also important for European manufacturers.

FDA-compliant requirements need materials that have a long shelf life while not releasing ingredients into the food.

The FDA is divided into various substructures. FDA21 stands for Food and Drugs, CFR for Code of Federal Regulations and Part 177 for Indirect Food additives: Polymers. This specific area of the FDA describes the approved polymers.

FDA-approved PTFE is required whenever the hose assembly is used in applications and/or equipment subject to FDA approval.

Our PTFE tubing systems use only PTFE liners with FDA 21 CFR 177.1550 approval.

The hose cover and any intermediate layers are generally not designed in accordance with FDA, since they are not in contact with the medium in the intended use.

5.2 USP Class VI

Plastics used in medical technology and pharmaceuticals are divided into six biocompatibility classes in the United States Pharmacopeia (USP). To assign elastomers and other polymer materials to one of the classes, they are subjected to various tests to determine their biological reactivity in living organisms.

Based on binding guidelines for the manufacture of medicinal products and medical devices, the quality of the substances tested is to be guaranteed. The correct identity of the drug substance, active ingredient strength, quality, purity and composition are evaluated. In order to obtain a USP Class VI classification, the following tests are carried out on the material itself and on various extracts of this material in external testing laboratories. Roughly, three test fields can be distinguished:

– Acute systemic toxicity:
The determination of acute irritant effect by skin contact, inhalation and ingestion is carried out.

– intracutaneous reactivity:
The test material is placed in direct contact with the tissue for which it is intended in normal use.

– Implantation test:
The reaction after implantation into the tissue of a living organism is studied. The duration is usually five days.

These tests are performed at set exposure times and temperatures to ensure comparability of results. Although biocompatibility testing must take place on the finished medical device, it is important for the manufacturer that all starting materials used are also tested and meet the requirements of the final product.

USP Class XI is further subgrouped in detail according to EP 3.1.9. This subcategory specifies specific tests on silicone elastomers, such as the residual peroxide content.

Strictly speaking, USP Class VI approval is only required if the tubing is in continuous contact with human tissue.

Our PTFE hose systems use only PTFE liners with USP Class VI approval.

5.3 Freedom from GMO/BSE/TSE

In the pharmaceutical industry, it may be necessary to confirm freedom from GMO/BSE/ TSE. This is a declaration that the products are free from animal ingredients and materials of animal or cell culture origin:

– BSE (Bovine Spongiform Encephalopathy -' spongy change of the brain substance occurring in cattle)

– TSE (Transmissible Spongiform Encephalopathy -' transmissible spongiform brain disease).

– GMO (Genetically Modified Organism) The ADI-free certificate confirms that raw materials used in the manufacture of the elastomer do not contain any animal derived ingredients (ADI).

Our PTFE hose systems use only PTFE liners that are free of BSE, TSE, GMU and ADI.

5.4 Regenerate-free

Sometimes the property "regenerate-free" appears in connection with the material PTFE. This is completely irrelevant for industrial hose assemblies. Regenerate-free means that no PTFE residues with any toxic substances are reused in the manufacture of the PTFE liner. This may occur with low-quality elastomers (e.g. pond liners).

Our PTFE liners are always extruded from virgin PTFE (i.e. pure PTFE) or PTFE-carbon compounds (a fixed proportion of carbon is added to the virgin PTFE for this purpose).

5.5 Virginity/Conductivity

As described above, a distinction is made between virgin PTFE and PTFE compounds. Virginal PTFE is pure PTFE without further additives. PTFE compounds can usually contain carbon (to increase conductivity) or glass (to increase strength).

6. Technical properties of PTFE

7. Connection of the hose fitting

For the use of a hose assembly in the process industry, the hose is usually integrated with connection fittings.

In this process, a hose nozzle located in the hose is firmly connected from the outside with clamping shells or furrules. The combination of connection fittings and the hose creates a hose line - a pressurized component that is subject to the Pressure Equipment Directive.

When integrating the fitting, there are basically two design options for PTFE liners:

Flanged connections
Crimped connections

In the case of flanged connections, the PTFE liner is passed through the connection fitting and brought onto the sealing surface of the fitting by means of thermal deformation (lining or flaring). This results in a hose line that is 100% lined with PTFE: completely gap-free and with full protection against the medium. This is often used for highly corrosive media or processes with dead space free requirements (pharmaceutical/food applications).

In the case of crimped connections, the hose fitting nozzle inserted into the hose is crimped to the hose from outside with a ferrule by means of a crimping sleeve. This creates a transition inside the hose line between the PTFE liner and the material of the hose fitting nozzle (usually stainless steel).

8. Selection of the hose cover

9. The PTFE liner in detail

The cylindrical liner can be corrugated on one or both sides (inside/outside) by further processing. The corrugated shape increases the flexibility and the bending radius. What sounds simple is a complex process and patented at HygienicPureFlex®. Generally there are four possible surface structures of a PTFE liner.

*1 Corrugated: PTFE corrugated hoses feature a high-flow design, which guarantees a significantly higher throughput cross-section than competitor products (e.g. 35% more line throughput area for 1") due to the combination of corrugated design and wall thickness.

*2 "Flattened" means that the hose liner has a flexible, profiled outer surface, with a smoothed inner surface.

Markert offers the widest range of PTFE hose assemblies on the market: Hose liners in Teflon T62 quality and PTFE with Non-stick effect - perfectly smooth, with highly flexible corrugated structure, with flattened inner surface and profiled flex outer surface. In addition, there are five different hose cover qualities or just the liner - with or without vacuum spiral, with lined connection fitting and in other designs.

―› The PTFE product range guarantees the best solution for your application with over 40 different product base variants.

10. Which hose for which application

11. What can happen

12. Sustainability

13. Why Markert filter and hose technology

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Contacts

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