Why use PTFE seals?Polytetrafluoroethylene (PTFE) is a thermoplastic polymer that can be used in a variety of sealing applications; it is particularly suitable where the application conditions exceed the parameters of elastomeric seal use, but are not as highly demanding as applications that require the use of metal seals.
What is PTFE?
Discovered accidentally in the DuPont™ laboratory in Jackson, New Jersey, USA in in 1938. The molecular structure of PTFE is based on a linear chain of carbon atoms which are completely surrounded by fluorine atoms. The carbon-fluorine bonds are among the strongest occurring in organic compounds. As a result PTFE has thermal stability across a wide temperature range. It’s high melting point (342 °C) and morphological characteristics allow seal components made from virgin PTFE to be used continuously at service temperatures of up to 260 °C, and with the addition of fillers – up to 300°C. It has the unique ability to resist material degradation, heat-aging and alteration in its physical properties during temperature cycling. Alongside this rare combination of material characteristics PTFE also has unlimited shelf life.
Why use PTFE seals?
Notably PTFE demonstrates extraordinary chemical resistance: the intrapolymer chain bond strengths preclude reactions with most chemicals, thereby making it chemically inert at elevated temperatures and pressures with virtually all industrial chemicals and solvents. Only a few media (some molten alkalis) are known to react with PTFE seals making them the perfect sealing solution for highly aggressive chemical applications. PTFE also has the lowest friction coefficient of any known solid; it has self-lubricating capabilities which offers continuous dry running ability in dynamic sealing applications and has superb stick/slip capabilities.
Focus on dry coatings
The advantages of using PTFE in sealing applications are; functionality at high and low temperatures, dynamic sealing with high wear capabilities, high pressure sealing (using combinations of PEEK back-up rings) and compatibility with highly aggressive chemical combinations. Our range of PTFE seal products include back-up rings, rod and piston seals, slipper seals and spring energised seals in a wide variety of sizes. Materials depend on application requirements but we offer a wide range from Virgin PTFE or including filler combinations of MoS2, glass, carbon, carbon fibre, graphite, and bronze. These characteristics make PTFE seals perfect for the demanding applications involved in Oil & Gas, Aerospace, Automotive and Chemical Process markets (to name but a few) and Ceetak’s engineering team are experienced in the design of PTFE sealing solutions to meet the complex specifications these types of application demand. Read our overview and more detail about PTFE seals HERE
Why use PTFE seals? 
Perfluoroelastomers in valvesIs it time to re-visit using perfluoroelastomer seals in your valves? First developed by DuPont™ in the late 1960s, perfluoroelastomers (or FFKMs), are now widely known and understood in a variety of markets. But for those that may be less familiar with these high performance materials, here is a quick recap...
What are perfluoroelastomers (FFKMs)?
They are essentially highly or fully fluorinated compounds with a fluorine content above 75%, and they offer outstanding chemical resistance. Generally better than all other elastomer types, FFKMs are often referred to as having the resistance of PTFE but in elastomer form. The term “universal” chemical resistance is commonly used; although it’s not strictly true as we will learn shortly. Unlike PTFE, the molecular make-up of FFKM includes crosslinks (or spring-like elements). This is contrast to just a backbone of carbon-carbon atoms surrounded by protective fluorine atoms. These crosslinks are what give the FFKMs their crucial elastic behaviour (in other words returning quickly to their original shape after being deformed). But the crosslinks are also a drawback as they can be a weak point for a chemical attack. Different crosslinking systems can be used when developing FFKMs and the choice will determine the high and low-temperature capabilities. Compounds developed for extreme high-temperatures (up to around 325oC) generally have a less broad chemical resistance. This is in comparison to the lower temperature grades (up to 225oC). Similarly, FFKMs developed to have excellent resistance to specific fluids (such as amines or high-temperature steam) can have limitations of low-temperature capability or compression set. As a result, there is no universal material that covers all application criteria bases.
A variety of grades
Previously the number of perfluoroelastomer grades was less prolific than other elastomer types such as FKM, EPDM, and NBR. However more than 50 years of technical developments have created a range of FFKM grades for specific and challenging applications. These are particularly in chemical process, oil and gas, semiconductor, and aerospace industries. Additionly, options with a hardness range of 65 to 90 durometer, and versions that meet international standards or specifications for food, medical, CPI, and oil & gas applications means the portfolio of FFKM-based compounds available to engineers is now substantial. In addition to technical developments, manufacturers and compounders have also been addressing the only real drawback of FFKM materials; the cost. They are difficult and time-consuming base polymers to manufacture. With a relatively low volume production base and sometimes lengthy processing times, FFKM seals carry a high financial premium over FKM seals. Even several times greater than FKM itself has over NBR. In recent years, there’s been more focus on making general-purpose grade FFKMs with broader temperature and chemical resistance capabilities more financially attainable. The initial procurement costs remain high compared to less capable elastomer bases. The overall cost of ownership may now be more appealing than it was twenty or even ten years ago. The ability of FFKM seals to survive for much longer in applications where exposure to a variety of fluids (perhaps wider than originally specified) is possible. This considerably reduces unplanned costs associated with maintenance and downtime.
Focus on dry coatings
The cost of unscheduled maintenance and repair in pump and valve equipment can be high in any industry, but exceptionally so in petrochemical, oil & gas, and semiconductor. When these costs are fully considered in the overall lifetime of a product, the initial price of seals in a valve is considered relatively minor, but it can still be a barrier in the material selection process. With both technical and commercial developments in recent times FFKM materials now compare more favourably against other materials for static, or low-duty dynamic applications in valves. In applications where persistent and sporadic issues keep coming back to cause problems, they are now a more financially attainable choice of material to avoid re-work, overhaul, downtime, customer dissatisfaction, and ultimately, more costs. Read more about FFKM as a suitable sealing material HERE
Perfluoroelastomers in valves 
Seals for Semiconductor ApplicationsSemiconductor and electronics manufacturers are facing greater demands for more complex and powerful devices to fulfil applications across all industry segments. High performance seals and ultra high purity elastomer materials are crucial for these critical applications.
Characteristics of Semiconductor sealing
The technology push for more complex devices requires semiconductor companies to research and design new methods of processing within their manufacturing cells. Consequently, there’s an increase in challenging technical conditions. These include complex chemistry, increased temperatures and stringent cleanliness within manufacturing process and the surrounding tools. The need for high performance seals for semiconductor applications is greater than ever. Component and material suppliers are challenged with these complexities. They must adhere to the same rules, ensuring all the criteria for these new processes are met. Including the combined effects of the outlined above conditions. Our world demands modern performance materials for the semiconductor industry. It is therefore apparent materials previously formulated for older generation tools may not be technically capable in new and future applications. Therefore, it’s paramount to investigate and formulate new performance materials that meet each specific application.
Wet Cleaning and ECD
Wet cleaning is a method used in semiconductor manufacturing to remove any contaminants from each layer of the wafer surface, usually by using chemicals and pure water. ECD is a method of laying down the bulk of the copper wiring within a semiconductor device. Compounds for wet cleaning are engineered for static and dynamic applications with minimal metallic ion contamination.
Thermal applications
Compounds for these applications are required to have excellent thermal stability and maintain integrity at elevated temperatures. These are often found in processes such as Oxidation, Diffusion, Annealing, and RTP. These processes are extremely challenging for seal materials. High thermal load at 300°C with temperature cycling can encourage compression set. Additionally, they must be manufactured to limit out-gassing at high temperature to prevent contamination within the process area and offer superior physical properties.
Thin Film and Dry Etch
Thin film deposition is the process of creating and depositing thin film coatings onto a substrate material. These coatings can be made of many different materials, from metals to oxides to compounds. Dry etch is a process for material removal. Thin Film applications such as HDPCVD, PECVD, SACVD, PVD and ALD, along with Dry Etch and Ashing processes present harsh plasma and gas environments, often at elevated temperatures. Whereas traditional seals might deteriorate and fail in these conditions, our next-generation compounds have excellent chemical and thermal resistance. Consequently, they are virtually impervious to extreme fabrication processes, therefore excellent for semiconductor seals. Plasma processes are a very hostile and aggressive environment for seal materials. The corrosive chemistry at temperatures up to 250°C means that compounds must be chemically and thermal stable across the operating range and must include low-outgassing and low particle count features. These applications are varied; from window and door seals, chamber lid seals, valve seals, exhaust flange seals- each requires application knowledge to ensure all technical parameters are met before materials are recommended.
Ultra High Purity (UHP) materials
Perfluoroelastomer materials
FFKM’s contain fully fluorinated polymer chains. Subsequently, offer the ultimate performance from an elastomer for applications where the seals are exposed to high temperatures and aggressive chemicals for plasma, wet and dry, semiconductor process applications. There is an extensive range of FFKM materials available; the challenge is choosing the correct material grade for an individual application as one perfluoroelastomer will not cover the broad spectrum of requirements across all semiconductor process conditions. For example, some materials are better than others at high temperatures, some demonstrate better chemical resistance and some are poor at thermal expansion. Several compounds within our range of PERFREZ® perfluoroelastomer materials offer the best performance characteristics based on high thermal values, excellent low out-gassing and low particle count. We also offer a hybrid material which is an excellent “all-rounder” as it’s chemical formulation falls between FKM and FFKM. This means it performs consistently under slightly less demanding application conditions and with the added benefit of lower cost of purchase versus ultra-high grade FFKM’s. Other compounds within our range are very specific to semiconductor process applications such as CVD, PVD, Plasma Etch (oxide & metal), fluorine and oxygen compatibility with a high temperature threshold material for sub-fab NW /ISO exhaust line environments. As new challenging processes emerge within the semiconductor industry, further progress in high temperature materials above 300° C will be developed; we expect to add a new generation material for plasma applications to our portfolio of materials by the end of 2022.
Cleanroom Manufacturing
When producing seals for semiconductor applications, cleanroom manufacturing is essential. Semiconductor cleanrooms must be designed to control static, out-gassing, and any contamination from external particulates. For example dust, dirt, airborne microbes, and aerosol particles. Just a single particle of dust or debris on a wafer or component is enough to cause a catastrophic defect (that will ultimately lead to failure of a device). It is created and maintained by removing the air, circulating it through a filtering system and distributing (the clean and filtered) air back into the cleanroom environment. This can be achieved at varying levels of cleanliness, depending on specifications for the individual manufacturing environment or the finished product requirements. Different cleanliness levels are classified by the concentration of airborne particles within a measured space. Additional factors to consider are the manufacturing environment for the semiconductor itself. Furthermore, it’s important to ensure any auxiliary products (such as seals) brought into the environment also maintain the same levels of cleanliness. We provide a complete cleanroom production process; from material blank production through to inspection and packaging using controlled materials within state-of-the-art cleanrooms. Our clean room manufacturing facilities are Class 7 (10,000) manufacturing and Class 5 (100) inspection, cleaning, & packaging. Read more about our expertise in the semiconductor industry and how we can help you with your seals for semiconductor applications HERE
Seals for Semiconductor Applications 