Unravelling Polymers

The Definitive Blog on Polymers by Poly Fluoro Ltd.

ePTFE Membranes - The Possibilities are Endless

It doesn’t require a scientist or an engineer to take a basic property of a material and extrapolate the possible areas of application.

We have spent the last one year developing ePTFE membranes, as we saw it as a key growth area within the PTFEspace. As a technology, it remains obscure. Yet the demand for this product is so vast that it is no wonder that the few companies that have perfected it have been able to command the market (and by extension, the price).

To say that we have perfected ePTFE membranes would still be an overstatement. Being an SME, we have had to focus our R&D in those areas where clients have shown interest, rather than take a broader approach and simultaneously develop multiple variants. However, in our pursuit of client satisfaction, there have been consistent findings that have slowly allowed us to start tapping into the broader demand in the market. In addition to this, what we know about the property of the material gives us insights into other, perhaps less explored areas of application.

To start with, let us lay out the most fundamental property of this material:

ePTFE membranes allow gases and vapours to pass, while restricting liquids

This ability is what lays the foundation for the myriad applications (and potential applications) of ePTFE membranes. When coupled with the other properties of PTFE – such as temperature resistance, chemical inertness and dielectric strength – it is easy to see why the product is so much in demand.

  1. ePTFE Membranes in Automotive Vent ApplicationsAuto is a well traversed industry for ePTFE usage. We started our development of ePTFE membranes when we were asked to replicate an automotive vent as manufactured by Gore. The vent is a small disk of ePTFE membrane, with an adhesive backing. We were able to develop it in both virgin form and with a carbon filling.

    The purpose of this vent is to sit on a small opening at the back of the headlamp chamber. Any moisture that could potentially fog the headlights and/or condense within the chamber is released via the vent. However, as the vent is only permeable to gases and not liquids, water is no allowed back into the headlamp chamber, keeping it free from moisture.

    automotive vent

  2. ePTFE Membranes in PCB applicationsThe effect of moisture on PCBs is well known. Apart from rust and corrosion, the presence of excess moisture can cause multiple short circuits, destroying the device within which the PCB is operating.

    ePTFE membranes are ideal in allowing any moisture built up within the PCB assembly to escape. At the same time, in the event of direct exposure to liquids, the ePTFE membrane shields the PCB, keeping it dry.

    The usefulness of this application is seen in nearly every industry where electronics are used. With mobility becoming more important, the chance of exposing a device to moisture becomes nearly unavoidable (think, dropping your smartphone into water). Having the protection of a breathable ePTFE membrane means the device is less likely to fail in such an event.

    eptfe pcb

  3. ePTFE Membranes in Cable WrappingWe have covered this in an earlier post. However, it is useful to reiterate that the high dielectric capabilities of ePTFE drive its use as a cable wrapping medium.

    ePTFE insulator tape can be made with tightly controlled thicknesses of as little as 0.05mm, with a uniform density, and dielectric constant. Wrapping individual conductors in ePTFE can cut interference, noise, cross-talk, and signal attenuation. In some applications, ePTFE tape helps limit phase shift to 4.3° and signal attenuation to 0.05 dB at 110 GHz.

    ePTFE Cable

  4. ePTFE Membranes in FiltrationMultiple applications within filtration exist for the use of ePTFE. Filtration itself requires different levels of porosity and pore size and the membrane needs to be customised accordingly.

    One of the most commonly known filters is used in vacuum pumps. It consists of a single ePTFE layer, moulded into a polypropylene housing (see below).

    eptfe filter

  5. ePTFE Membranes in DesalinationWe believe this may be a huge growth area going forward. Desalination is an expensive process currently. An ePTFE layer could be used to allow for evaporated vapours from a salt water reservoir to pass through it and into an upper chamber. Consequently, it would prevent the condensed liquid from re-entering the salt water reservoir. In this manner, the water is separated from the salt using only solar energy. Spread over a wide enough area, this could effectively trap evaporating sea water to convert to fresh water.

We expect to continue adding to this list as more uses of ePTFE membrane become apparent. One thing we do know is that is a material of the future and that being able to modify and customise its texture and form would be a key proprietary skill going forward.

PTFE Pricing Update - The Impact of Anti-dumping Duties

For anyone connected to the PTFE industry, the last 18 months have been fraught with anxiety. The shutting down of a few PTFE resin manufacturers in China in early 2017 caused a supply crunch that has yet to ease out, driving prices up as much as 60%.

Many believed that the imbalance between demand and supply of PTFE raw materials would spur a capacity expansion from those manufacturers still operational. However – as we earlier saw in 2011 – resin manufacturers opted instead to maintain capacity and allow prices to increase. From the point of view of companies like Gujarat Fluorochemicals (India) and Shangdong Dongyue (China), this appears to be a sensible strategy. Until early 2017, the price of PTFE resins had been steadily declining due to fierce competition between resin suppliers. The shutting down of Chinese plants would have come as a blessing for these companies, who have since seen their realizations increase.

But while a rational observer may argue that an upward price correction was certainly due in early 2017, pinpointing the “fair” price for PTFE has always been tricky. Not only is the PTFE industry minuscule in comparison to more familiar polymers such as PVC, Polypropylene and Polyethylene, but its irreplaceable properties as an engineering plastic allows resin manufacturers a lot of leeway to test the extent to which higher prices would be accommodated by processors such as ourselves. Considering the price increase has been a worldwide phenomenon, it has not been impossible to convince clients regarding the upward revision of rates. What has been taxing, is the instability. A client may be willing to revise rates once or twice, but when it becomes a monthly affair, one can expect some backlash.

Amid all the uncertainty, it appears processors may have found some solace in the protectionist tendencies of the current US government. When the US announced in October 2017 that they would be reviewing the anti-dumping policy in relation to PTFE resin supplies, no one took much notice. This administration has highlighted multiple instances where the competitiveness of the US economy was threatened by low-cost-countries. We never believed that much attention would be paid to a niche industry like PTFE.

Over the past week, however, tariffs of 69% to 208% were announced on Chinese manufacturers, while Gujarat Fluorochemicals (India’s only manufacturer) was slapped with an 18.5% anti-dumping duty. The resulting impact of this measure is something we would like to extrapolate.

  1. Demand realignment

    The first and most obvious effect of a tariff such as this is to curb demand from the US for Indian and Chinese resins. Globally, North America is said to contribute to about 25% of PTFE demand, with the bulk of this coming from the US.

    Our understanding of the price of Chemours resins (the erstwhile DuPont and the company that has lobbied to get the anti-dumping duties imposed) is that they lie between 1.25-1.6 times the price of resins from India. Hence, even with freight and other duties, Indian suppliers may still find some takers in the US market. It should however be noted that given the superior quality of Chemours’ material, processors cannot be expected to choose Indian resins, should the price differential be small.

    With regards to China, the pricing is a little more opaque. There are several manufacturers, and each has their own rate contracts with their respective clients. Whether a 208% tariff is warranted or is merely the result of effective lobbying on the part of Chemours, we cannot really tell.

    In a twist of undeniable irony, Russian manufacturers have been omitted from this tariff. When Gujarat Fluorochemicals successfully lobbied for anti-dumping duties into India, they made it a point to include both China and Russia in their report. The absence of Russia from the US’ anti-dumping measures means that they are well poised to benefit from the demand shift – assuming the US does not penalize them with any other general trade tariffs.

  2. Supply realignment

    Considering what a large share of the world’s demand the US commands, their focus inward will leave a lot of Indian and Chinese resin manufacturers in the cold. The move is likely to cause the capacities of Asian firms to come in line (if not even exceed) local demand. There is still a significant amount of demand within Asia Pacific – which accounts for more than 50% of the global market. However, the price points are lower and the fact that the US has practically shut its doors mean that competition will drive prices down again.

    This may be particularly harsh for Indian resin manufacturers, as Chinese resins – which have been hard to come by locally due to the supply crunch – will undoubtedly flood the market. Interestingly, the anti-dumping duty on Russian resins into India has expired recently, implying that here too, they have a good opportunity to enter the market.

  3. Value realignment

    When India imposed anti-dumping duties on China and Russia back in 2010-2011, the effect was not as beneficial to Indian resin manufacturers as initially assumed. This was because processors shifted their demand from buying raw materials from China to buy semi-finished goods. Traders who were earlier importing resins, now began dealing in rods and sheets.

    It is therefore equally likely that in the US too, the market will shift such that semi-finished and finished components get imported, rather than resins. Ultimately, the US has a significant appetite, and this needs to be met one way or another. One cannot imagine a processor in the US agreeing to pay a 200% duty, when they can just as well import finished products with no such penalty.

    It should also be noted that while Chemours may certainly want to monopolize the North American market as it once did, it simply may not have the capacity to satisfy the local demand. As a result, shortages will push clients to look further up the value chain for their requirements. In protecting the interest of a few large companies, the US may have just killed of a large portion of its processing industry, which was no doubt dependent on Indian and Chinese resins for staying competitive.

PTFE (Teflon ) Tubes as Insulators

The benefits of PTFE as an electrical insulator are well known. The high dielectric strength and breakdown voltage of PTFE allows it to be used in applications where standard insulation materials would fail.

In our experience, we have seen PTFE skived tapes used as wrapping around high-voltage junctions and circuits, PTFE components used as transducer covers and high-voltage casings and PTFE pads used to shield metal bodies from one another in electrical and thermal applications.

PTFE (Teflon®) tubes find similar uses as electrical insulators, although one really needs to dig deep to see where exactly they are used. Ever since we started manufacturing PTFE (Teflon®) Tubes, we have begun exploring its application and approaching various clients currently making insulation assemblies to understand whether there is a possibility to use PTFE in their products.

PTFE (Teflon®) Tubes in Cables

The requirement of cables to have a single outer casing that houses a variety of conductors necessitates the use of an insulating medium. PTFE tubes are used to shield each conductor from the next. In this application, it is essential that the tube is both flexible and free of any cracks/inclusions that would affect the insulating properties.

Additionally, since the requirement may be for a cable that is continuous and without joints, the PTFE tube would itself need to be continuous. It is therefore imperative to be able to manufacture a continuous tube that would be free from any defects for a length of at least 150 to 300 meters.

It has taken extensive research and multiple trials to attain a level of extrusion that guarantees a flawless, continuous length of tube.

PTFE Tube forms the insulating medium around the cable core


PTFE (Teflon) Tubes in Short Neutral Sections

While the tubes used inside cables are usually thin-walled tubes (within 1mm wall thickness), there are applications where thick-walled tubes form the outer casing of insulating assemblies.

The Short Neutral Section (SNS), is an insulating assembly used in overhead lines for the railways. Typically, the pantograph will run along a high-voltage wire above the train, allowing current to be supplied to the train. The current is drawn from a sub-station and when switching from one sub-station to the next, the pantograph will pass over the neutral section. The assembly ensures that the wires from two separate sub-stations do not make contact. Hence, it is important for the insulating medium to be effective. Furthermore, since the pantograph runs over the neutral section at high speed, it requires an insulator that is also capable of high wear resistance.

We were approached by the railways to develop this assembly. The core of the product is the thick-walled PTFE tube, which is combined with additives to improve wear resistance, while maintaining the dielectric properties.

PTFE Tube used as an outer sheath for electrical and wear properties

Conductive or Anti-Static PTFE Tube

Because PTFE has such a high resistance to current, there are areas where this becomes a problem. With no way to pass through PTFE, there is the possibility that excess static discharge simply collects on the surface of the material. Once a critical mass of discharge is reached, there is a high possibility of sparking.

In applications involving flammable vapours, such sparking can be very dangerous. To mitigate this issue, fillers such as carbon are added to PTFE to allow for some static discharge to take place through the material. The addition of carbon reduces the insulating properties of PTFE to some extent, but the end properties of the material are still far above any regular insulators.


There are multiple other uses for PTFE (Teflon®) Tubes across industries. As old designs are upgraded, it is important for product designers to keep in mind that PTFE has properties that make many of the older insulating materials obsolete.


Note: Teflon® in the registered trademark of Chemours™