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 = 32) 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.
TFM © by Dyneon is the name for “Modified PTFE” and is also called the second generation of PTFE (Polytetrafluoroethylene). The difference compared to conventional PTFE is that with TFM ©, the slight addition of oxygen shortens the chain length of PTFE and also increases the cross-linking of the molecular chains. 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 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. TFM © and conventional PTFE have the same universal chemical resistance. On the other hand, components with fillers based on TFM © instead of PTFE can further increase compressive strength and abrasion resistance.
A further improvement in the properties of TFM © compared to 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 TFM © 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 technology or in the pharmaceutical and food industries. Critical joint gaps can be avoided here by welding components together.
PFA stands for perfluoro-alkoxy
PFA has approximately the same properties as PTFE. Due to the shorter chain length, caused by the embedded oxygen atom (O), 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 low heat resistance in the low-temperature range.
PCTFE stands for polytrifluoroethylene
PCTFE has a lower chemical resistance than PTFE or PFA. The ability to use heat is also 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 stands for polyvinylidene fluoride
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 tempered at 13°C have particularly good mechanical strength values. However, the polar structure of the material excludes its use in high-frequency technology.
ECTFE stands for ethylene-chlorotrifluoroethylene copolymer
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.
ETFE stands for the copolymer of ethylene and tetrafluoroethylene
Thanks to its 25% ethylene content, the thermal processing of PTFE is greatly improved. However, chemical resistance and thermal application possibilities are limited to the range of -190 to +155°C. Suitable for the production of injection moulded parts.
PEEK stands for polyether ether ketone
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. Due to its high tensile strength and its elasticity modulus, it is considerably notch sensitive.
POM stands for polyoxymethylene
POM is an all-rounder among the variety of today’s plastics. Heat resistance ranges from -20 to +130°C and 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 processed 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.