Unravelling Polymers

The Definitive Blog on Polymers by Poly Fluoro Ltd.

Expanded PTFE (ePTFE) Tapes vs Thread Sealant Tapes - What's the Difference?

When you manufacture a specialised product, one of the biggest challenges lies in ensuring the end-user recognises the technical advantages of the same. This is especially true when there are cheaper substitutes that compare with your product visually, implying the end-user might have doubts on whether you are selling him anything special, or whether you are simply charging a premium over something commoditised.

Expanded PTFE (ePTFE) Tapes are one of the most specialised variants of PTFE. Their uses go from simple gasket applications, all the way to intricate membranes for use in high-end filtration and medical membranes. However, the similarity between ePTFE Tapes and Thread Sealant Tapes (also called: Plumber’s Tape), can sometimes confuse clients, who might question whether they are not one and the same.

Thread Sealant Tape is a highly commoditised PTFE tape that is cheaply available in nearly any hardware store. As its name suggests, it is mainly used in plumbing, where it is wrapped around the threads of a pipe, before a mating pipe is tightened over it. The ability of the tape to easily take the shape of the existing threads means that it creates a tight fit, thereby preventing water leakage. Plumber’s Tape is a highly useful material in its designated application. However, it has grave limitations when compared with expanded PTFE (ePTFE) Tape.

Differences in Production

There exist many key differences in the production process. Thread Sealant Tape is made by extruding a bead of PTFE, which is then passed through various calendaring, slitting and spooling operations. The end result is an unsintered PTFE tape with a thickness of ~0.075mm (75µm).

Expanded PTFE (ePTFE) Tape is also made by first extruding the tape. However, this tape is then put through a drying process, after which it is passed through a stretching machine at elevated temperatures. The stretching process needs to be CNC controlled in order to ensure the stretch rate, speed and temperature are maintained as per strict parameters. The resulting tape would usually have a thickness ranging from 0.25mm to 15mm

The fact that Thread Sealant Tape is calendared, unsintered tape, while ePTFE Tape goes through a stretching and heating process is the reason the tapes exhibit such different properties.

Differences in End Properties

As mentioned above, the key purpose of Plumber’s Tape is to seal leaks in piping. The unsintered PTFE material is soft and easily takes the shape of the threads that it is wrapped around.

In contrast, ePTFE Tapes exhibit a range of properties, in addition to sealing, which make them vital across a number of industries. To start with, as a sealing material, ePTFE is used in areas where you not only require a seal, but where the seal needs to be capable of taking high pressures (up to 100Bar), high temperatures (up to 250°C), and be resistant to a range of corrosive chemicals. Trying to use simple Thread Sealant Tape in such demanding environments will cause the tape to degrade almost instantly, as it lacks the mechanical strength to withstand the same.

Expanded PTFE (ePTFE) also has high dielectric properties. The tape can resist immense levels of voltage and is used in high-end cable wrapping to improve efficiency and insulation. Again, some cable manufacturers do try and use Thread Sealant Tape to wrap around cables, after which the cables are sintered in order to fuse the tape. However, the resulting cable has a much lower insulative capacity and may tend to fail in higher intensity applications.

Finally, expanded PTFE (ePTFE) exhibits micro porosity. The calendaring process used in making Thread Sealant Tapes ensures that there are no pores in the material. However, because ePTFE is stretched under high temperatures, it attains a level of porosity. Most notably, ePTFE exhibits hydrophobic and oleophobic properties, meaning it repels water and oil respectively. At the same time, the material will allow the passage of vapours. This unique characteristic makes it an invaluable material in venting and filtration applications. It also allows ePTFE Membranes to find use as grafts and stents for use in the medical industry.

The combination of these properties ensures that ePTFE is demanded not only in fluid sealing systems, but in filtration, medical, heavy electricals, chemical plants and even aerospace applications.

When you consider the above points, it is easy to see that ePTFE Tape and Thread Sealant tapes are worlds apart in terms of their effectiveness and their breadth of application. Nonetheless, it should be noted that many applications are basic enough that using Thread Sealant Tapes might suffice. Commercially speaking, ePTFE would cost many multiples of what a simple Thread Sealant Tape costs. Hence, the decision to use ePTFE rests on the end application itself and on whether the required properties of the material need to extend to as high as what expanded PTFE offers.

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