The properties of PTFE as a food grade material that can be machined to close tolerances is often exploited in applications where any kind of chemical contamination needs to be avoided at all costs. 

Recently, we were asked to develop a set of chevron v-seals made earlier with PTFE infused fabric, specifically to be used in the dairy industry. Our study into the existing seals being used by the client told us that the PTFE infused fabric was no longer the best option for what the client required. Fabric based components were first developed over thirty years ago and were a mainstay for many OEMs. Over time, as PTFE compounding techniques improved and the uniformity of the blend became consistent, these seals were replaced by either virgin PTFE seals or PTFE with fillers of glass, Ekonol (aromatic polyester), or even PEEK.

One of the primary reasons PTFE seals are used in the food industry is because of their resistance to chemical and biological contamination. PTFE is non-reactive to most chemicals and food ingredients, making it an ideal material for seals that come into contact with food products. Additionally, PTFE is naturally hydrophobic, which means that it repels water and other liquids, making it resistant to mould, bacteria, and other biological contaminants. This is especially important in the food industry, where contamination can lead to serious health risks for consumers.

Another important characteristic of PTFE seals is their durability and longevity. PTFE is a highly stable material that is resistant to most forms of physical and chemical degradation, including high temperatures, corrosive chemicals, and UV radiation. This makes PTFE seals ideal for use in food processing equipment that is subjected to harsh conditions, such as high-pressure washdowns, heat, or exposure to corrosive substances.

In addition to their resistance to contamination and durability, PTFE seals are also an ideal choice for the food industry because of their low friction coefficient. This means that they can easily slide against other materials without sticking or causing wear, which is important in applications where high-speed movement is required, such as in conveyor systems or packaging equipment. PTFE seals can also operate at a wide range of temperatures, from -200°C to 260°C, which makes them suitable for use in both cold storage and high-temperature cooking applications.

There are several applications in the food industry where PTFE seals are commonly used. One of the most common applications is in the sealing of rotary valves, which are used in the transfer of bulk materials such as powders, grains, and liquids. PTFE rotary seals are ideal for this application because they can withstand the abrasive and corrosive nature of these materials, while also maintaining their sealing properties over time.

PTFE seals are also used in other food processing equipment such as pumps, mixers, and blenders. These seals help to prevent the leakage of fluids or the ingress of contaminants into the equipment, which can compromise the quality and safety of the food products being processed. In addition, PTFE seals are often used in high-speed conveyor systems, where their low friction coefficient helps to minimize wear and ensure smooth movement of the food products. As a soft polymer, PTFE is unique in that it can take a tremendous amount of load (both mechanical and environmental), but that it will ultimately succumb to any major misalignment of mating metal parts. This means that in the event of failure, the seal will allow itself to be destroyed rather than damage the otherwise expensive equipment that it functions within.

The effectiveness of PTFE seals in ensuring the quality and safety of food products is unmatched. With their excellent performance characteristics and versatility, PTFE seals will continue to play an important role in the food industry for years to come.

---

Read More

1. Polymers in Food Processing

2. Expanded PTFE (ePTFE) Gasket Tapes - Applications in Electrolysers

3. Polymer Scraper Blades - An effective, non-damaging solution to automation systems

The onset of the green energy revolution has led to a burst of technologies around the generation and storage of clean electricity. A key advantage of erstwhile coal and gas-powered plants over their renewable energy counterparts is that power generation could be started and stopped with a flip of the switch. This also ensured that storage was not a key concern since electricity is available ‘on tap’ as it were.

With both solar and wind power, in contrast, power generation depends on the elements and the intensity with which they choose to act. While wind energy can vary erratically depending on the force and direction of the winds, solar power is available mainly during certain peak hours of the day, although devices like solar trackers allow us to maximise the energy we harvest during these hours.

The other issue, of course, is storage. With renewable energy, the ability to store becomes critical to ensuring that the supply to the grid does not suffer the same vagaries as the energies received. 

One of the main methods to store energy uses green hydrogen.

Green hydrogen involves using the harvested energy to power an electrolyser, which in turn converts fresh water into hydrogen and oxygen. This hydrogen is then stored in tanks and later burned (the by product being water) to create power for the grid. Across the world, companies are scrambling to set up green hydrogen plants, as they form a critical link to allow renewable energy to become the mainstay for future power needs.

In this endeavour, the efficiency of the electrolyser becomes paramount in ensuring that minimal energy is lost in the overall process. 

An electrolyser is a device capable of splitting water molecules into their constituent oxygen and hydrogen atoms. It consists of a conductive electrode stack separated by a membrane to which a high voltage and current is applied. This causes an electric current in the water which causes it to break down into hydrogen and oxygen. 

At present, there are different types of electrolysers depending on their size and function. The most commonly used are:

Alkaline electrolysers

They use a liquid electrolyte solution, such as potassium hydroxide or sodium hydroxide, and water. Hydrogen is produced in a cell consisting of an anode, a cathode and a membrane. The cells are usually assembled in series to produce more hydrogen and oxygen at the same time. When current is applied to the electrolysis cell stack, hydroxide ions move through the electrolyte from the cathode to the anode of each cell, generating bubbles of hydrogen gas on the cathode side of the electrolyser and oxygen gas at the anode. 

Proton exchange membrane (PEM) electrolyser

PEM electrolysers use a proton exchange membrane and a solid polymer electrolyte. When current is applied to the battery, water splits into hydrogen and oxygen and the hydrogen protons pass through the membrane to form hydrogen gas on the cathode side. They are the most popular because they produce high-purity hydrogen and are easy to cool. They are best suited to match the variability of renewable energies, are compact and produce high-purity hydrogen. On the other hand, they are somewhat more expensive because they use precious metals as catalysts.

Expanded PTFE (ePTFE) in electrolysers

Given the presence of liquids and chemicals, it is imperative that proper sealing exists between the stacks of the electrolysers. In this regard ePTFE tapes are used between the stacks to provide superior sealing. Expanded PTFE not only has a compressibility of up to 60% - allowing it to make a very robust seal even at low torques – but is also weatherable, resistant to chemicals, and highly effective even in extreme pressures. The exact dimensions of the ePTFE tape can vary from project to project, depending on the construction of the electrolyser. However, a thickness of 1.5-2.5mm is typically used with a width of 25-50mm. The tape is easily applied and can even be layered on to itself, eliminating the use of a standard cut gasket. This is relevant because the diameters of the electrolysers can be as high as 2 meters, meaning that a standard cut gasket would be very wasteful. Considering that a 5 MW alkaline electrolyser requires around 500 seals, this saving is particularly vital.

Over the past few years, a number of green hydrogen projects have shifted to ePTFE for the sealing of the electrolysers. While other materials such as EPDM, Low-hardness FKM, and butyl have all been tested and found reasonably effective, the efficacy and ease of use of ePTFE has proven unparalleled. It is likely that in the coming years, ePTFE gasket tapes will be a mainstay of any electrolyser plant.

---

Read More

1. Polymer Scraper Blades - An effective, non-damaging solution to automation systems

2. PEEK Manifolds - High Precision Components for Fluid Control Systems

3. High-Performance Polymers in Oil & Gas Applications

 

The advent of mechanisation, automation, and the use of robotics in manufacturing shows no signs of slowing down. One of the critical requirements of such systems is continuity. Any automated system only works when each segment of the process functions smoothly and without any interruption. Considering the speed at which some of these systems move the smallest glitch can often push the entire manufacturing line to shut down.

Polymer scraper blades are primarily used to remove obstructions, clear surfaces, and remove sticky materials – such as glue or residual polymers from running systems. Their purpose ensures that debris and other materials are taken out of the process so that they may not cause jamming or scratch surfaces.

There are many advantages of polymer scraper blades in such applications. While metal blades were used earlier on, there is a lot of potential damage that can be caused by these. Polymers, in contrast are hard enough to be effective scrapers, but not so hard that they will damage other elements. Further, with polymers, a designer can choose the level of hardness needed, depending on the other materials the scraper will interact with. There are numerous polymers that can be thus employed.

PTFE (Teflon)

PTFE has multiple advantages as a scraper blade. The low coefficient of friction means that it can smoothly run over a system – such as a conveyor belt or glass surface – without putting any load on the other material. PTFE is also soft – so even delicate systems can benefit from PTFE scraper blades. However, the same softness places a limit on how sharp the blade edge can be made with PTFE. Although fillings of glass, carbon, and even stainless steel (see picture) can improve the stiffness of PTFE, its use is mainly beneficial where aggressive scraping is not needed.

UHMWPE

Like PTFE, UHMWPE has a low coefficient of friction. It is also lightweight and exhibits superior wear resistance. UHMWPE is also soft, so again, its use is limited in non-aggressive applications. Unlike PTFE, UHMWPE does not perform well in high temperatures. However, it is very cost effective, highly machinable, and does exceedingly well against rough materials, that would necessarily place a lot of wear load on the scraper blades.

Nylons

Both PA6 and PA6.6 perform well as scraper blades. The addition of Molybdenum di Sulphide further improves wear resistance while the inherent hardness of the material exceeds that of PTFE and UHMWPE. Nylons are light weight, but are also prone to moisture absorption, making them better suited to dry environments.

POM

One of the most versatile polymers, POM (Polyacetal, acetal, or Delrin) is an exceptional choice for scraper blades. Unlike PTFE, UHMWPE, or Nylons, POM is a harder and can be machined to a far finer and shaper blade edge, making it excellent for fine and even aggressive scraping. The addition of PTFE fillers to POM can help reduce the coefficient of friction further. Unlike PTFE, however, POM cannot work in temperatures above 150°C.

PEEK

PEEK combines all the best characteristics of the other polymers. It is very hard, making it possible to machine to a very sharp edge. The toughness of PEEK means that it can be used in very harsh environments – mechanically, chemically, and at temperatures in excess of 250°C. The blade will not dull easily and the addition of PTFE can help to make the material more smooth. However, such a swell of properties does come at a price. PEEK is at least 6-8 times more expensive than PTFE and about 20 time more expensive than POM. Hence, it’s use is limited in applications where nothing else can be used.

At Poly Fluoro, we have the capability to design, blend, mould, and machine the scraper blade that best suits the client’s application. The use of special blends can be incorporated, if the end-use calls for it, while the dimensions of the blade itself can be fine-tuned before bulk production commences.

---

Read More

1. PEEK Manifolds - High Precision Components for Fluid Control Systems

2. High-Performance Polymers in Oil & Gas Applications

3. PTFE Pricing Update - The Post-COVID Scenario