Fluoropolymers as the basis for high-performance fluoroplastics.

Rely on our expert knowledge about fluoropolymers.

In fluoropolymers, the hydrogen atoms [H] in the ethylene-hydrocarbon chain [C-H2]n are completely or partially replaced by fluorine atoms [F]. Accordingly, all polymers containing an ‘F’ in their structural formula have to be assigned to the fluoroplastic group. Since the fluorine atoms with their larger volume (atomic weight = 19) are considerably larger than the hydrogen atoms (atomic weight = 1), these form a dense and protective shell around the carbon chain and thus provide highly effective protection against chemical attacks. The very stable bonding of the carbon atoms with the fluorine atoms also results in high thermal strength, both in the high plus range and at low temperatures in the minus range.

TFMTM by Dyneon is a well-known trademark for “Modified PTFE” and is also called the second generation of PTFE (Polytetrafluoroethylene). The difference compared to conventional PTFE is that in TFMTM, the chain length compared to PTFE was reduced down to 1/5 th and additionally a side chain was introduced, which is linked by an oxygen atom to the polymer main chain. This modification mainly affects the mechanical properties of the material. In particular, the load-bearing capacity under compressive and tensile stress increases by up to approx. 35 % and thereby causes the so-called “cold flow” to be reduced (this is the deformation of a body under the permanent effect of compressive, tensile or bending stress). This is a highly appreciated improvement in properties, especially in the case of flat gaskets and dimensional stability of parts at elevated operating temperatures. Thus, the addition of fillers, such as glass fibres, can often be dispensed with. This is particularly the case when the requirements for the chemical resistance of the component exclude the addition of fillers. TFMTM and conventional PTFE have the same universal chemical resistance. On the other hand, components with fillers based on TFMTM instead of PTFE can further increase compressive strength and abrasion resistance.

A further improvement in the properties of TFMTM compared to the first generation PTFE is the lower porosity. This makes it possible to use smaller wall thicknesses for seals or insulators in electrical engineering and electronics. Since TFMTM also has a significantly higher weldability than PTFE, considerably more complex designs, e.g. from prefabricated, several individual parts, can also be achieved. An example at Beichler + Grünenwald for this type of design are various carriers (frames for wafers) which are intended for use in semiconductor industry or in the pharmaceutical and food industries. Critical joint gaps can be avoided here by welding components together.

PFA has approximately the same properties as PTFE. Due to the shorter chain length, approximately 1% compared to standard PTFE, a lower melt viscosity is achieved and the material – in contrast to PTFE – is injection mouldable. The disadvantage is the higher susceptibility to stress cracking and the permeation of polar, aqueous media at temperatures higher than appr. 180°C.

PCTFE has a lower chemical resistance than PTFE or PFA. Also the max. service temperature range is lower. Advantages are its injection mouldable property and greater hardness compared to PTFE and PFA and higher resistance to high-energy irradiation. Permeability is the lowest in the group of fluoropolymers.

PVDF is a partially fluorinated plastic, which nevertheless has very good chemical resistance. This material has the best resistance of all fluoropolymers to high-energy irradiation. Hot forming below the melting point by bending or stamping and deep drawing is very well possible. Semi-finished products that have been heat-treated at 130°C have particularly good mechanical strength values. However, the polar structure of the material excludes its use in high-frequency applications.

The main application is the production of pore-tight and corrosion-resistant powder coatings and container linings. Temperature range from -75 to 140°C. Suitable for the production of moulded parts by injection moulding, especially with glass fibre additives.

Due to its special, low-molecular weight polymer composition, the ability for thermal processing compared to PTFE is significantly improved. However, chemical resistance and thermal application possibilities are limited to the range of -190 to +155°C. It is also suitable for the production of injection moulded parts.

PEEK is a high strength plastic with excellent dimensional stability and is suitable for use at higher temperatures up to 250°C in continuous applications. The material has good chemical resistance to food, non-oxidising acids, alkalis, fats and oils. The material is injection mouldable and can also be processed very accurately by milling and turning. By adding graphite and PTFE, very good sliding properties with low wear can be achieved. Further benefits are its high tensile strength and the excellent elasticity modulus.

POM is an all-rounder among the variety of today’s plastics. Heat resistance ranges from -20 to +130°C and it is therefore suitable for general machine elements, fixtures and other structures subject to moderate loads. Material strength values largely correspond to hardwoods of beech or oak. It is injection mouldable and easily processable by turning and milling. Since POM does not absorb water, there is hardly any sign of ageing in a normal environment. For special applications, the resistance list should be observed if necessary.