Dryflex WS

With our Dryflex WS range we have turned the usual water-resistant properties of TPEs on their head to engineer materials that swell when immersed in water.

Hydrophilic TPE

Dryflex WS are a range of thermoplastic elastomers (TPE), which contain hydrophilic particles. They swell at a controlled rate and percentage when immersed in water. When there is no longer water present the compound shrinks back to its original size, a process of expansion and contraction that can be repeated. The materials have solid structural integrity; unlike many of the equivalent clay based products which can erode over time.

Dryflex WS - TPEs that Swell in Water

How would you use it?

Dryflex WS TPE - How would you use it?
Play Video

Dryflex WS+

We’ve further expanded the possibilities with the development of the Dryflex WS+ grades. These materials are designed for applications in high saline environments, such as sea walls, defences and water-stop construction. For example, in 8% saline solution at 23ºC Dryflex WS+ 51446 achieved double the volume swell of Dryflex WS 25E950 after 21 days. Dryflex WS+ 51446 had a volume swell around 300% compared to 150% for Dryflex WS 25E950.

Dryflex WS+ - Hydrophilic TPEs for Waterstops

Key Properties

Dryflex WS and WS+ materials are used in applications to form a positive seal and prevent the ingress or exit of water. We have also developed softer grades which offer excellent drapability. They are an ideal choice for water stop applications where the profiles may be coiled or need to be fitted around complex structures.

Compounded in any colour, the water swellable TPE is recyclable in closed loop systems and can be processed using conventional plastic fabricating methods, including extrusion and injection moulding.


Applications include

  • Waterstops
  • Water treatment plants
  • Tunnels, drains & sewers
  • Water tanks
  • Seals
Hydrophilic TPEs for Water-Stops

Hydrophilic TPE - How does it work?

Fig 1 : The hydrophilic ingredient is compounded into the Dryflex WS TPE at the time of manufacture.

Hydrophilic TPE - How it works - during

Fig 2 : After immersion in water the Dryflex WS TPE will expand uniformly, at a controlled rate and percentage.

Hydrophilic TPE - How it works - after

Fig 3 : When there is no longer water present the Dryflex WS TPE shrinks back to its original size.


From 350% to 1000% depending on the grade. Other swell rates can be formulated to meet specific application requirements.

It isn’t an ‘instant’ swell, it can take a number of days. Different grades swell at different rates. This is determined by :

  • the grade hardness
  • the formulated level of swell
  • environmental conditions
  • profile geometry
  • surface finish

Yes, higher temperatures will give a faster swell.

Both acid and alkaline conditions can affect the level of swell.

Increased levels of salinity reduce the level of swell.

Injection moulding & extrusion.

Between 25 to 40 Shore A for our standard grades

The optimal range is 25 to 40 Shore A. It can be possible to go to higher hardnesses but this will affect the swell and processing properties.

No, the material needs to be immersed in the water.

In general the compound is supplied in natural. We can colour compound to a basic palette. Natural compound can be masterbatched, we suggest a masterbatch with a LDPE carrier. Customers often use colour as a function rather than for aesthetics – it can be used to identity different swell rates of the different gradesPLEASE NOTE : The colour changes as the material swells!

Yes, this is one of the strengths of Dryflex WS.

Our Dryflex WS expert

Martin Bradbury

Martin Bradbury

Senior Key Account Manager for HEXPOL TPE Ltd

+44 161 654 2332


You can also visit our Downloads page for more brochures and information.

Dryflex WS Product Guide

Our product brands

More Dryflex TPE Ranges...