PEEK vs PTFE

For decades, valve manufacturers and valve users have suffered from the limited availability of ball valve seat materials. PEEK and PTFE are the two go-to materials of choice. So much so, that the habitual use of these two materials has left a void in performance, both physically and financially. Advances in materials processing techniques and quality processes are now starting to create alternatives that have clear competitive advantages for ball valve performance.

Given the stringent safety and quality requirements for valve seats, the selection of PTFE and PEEK has become an easy option as they have a proven track record and are recognised across the industry. This though does not come without it’s challenges. All too often PEEK is supplied under pricing pressure, which has caused the trusted use of PEEK on specifications to suffer from many quality and poor manufacturing practices;

This is an important subject but for now, let’s consider what is good about PEEK and PTFE and where their place is and isn’t for ball valve seats.

PTFE – what is it good for, where does it struggle

-         Good chemical resistance, low coefficient of friction, low moisture absorption, and high electrical resistance. but its flexibility at low temperatures is a key feature.

-         PTFE mechanical properties are low compared to other polymers and is very soft and cannot be used for higher pressures.

PEEK – what is it good for, where does it struggle

-         Outstanding chemical resistance, very low moisture uptake, good fire performance, excellent mechanical strength across a broad temperature range, and good dimensional stability.

-         Relatively High Cost. It is very hard and difficult for valve companies to seal with.

 So what is the gap?

Typically as pressure increases PTFE can no longer resist deformation well enough to perform long term, so PEEK is employed as the seat material of choice. Stepping from PTFE to PEEK causes a significant leap in price for valve seats. It also creates challenges around seal performance given that PEEK is so much harder and resistant to the slight deformation needed to seal against imperfections on the sealing face. Therefore, in a highly competitive landscape, moving to PEEK and the associated improvements in adjacent components and actuation can be the difference between winning and losing an opportunity. This is coupled with the influx of lower quality PEEK materials flooding the market, which can cause unreliable performance, prolonged testing due to quality issues and ultimately damaged brands and unplanned delays.

Is it about time to consider other materials as a potential solution?

Advanced material processing techniques are utilising physical properties of materials and creating high-performance characteristics without the problems with seal performance and extortionate price tags.

How can we address this challenge which is faced across the valve industry and what new developments are on the horizon?