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The material benefits of welded fabrics


Connect, no. 108, September/October 2000, p.8

A technique for welding thermoplastic fabrics, which melts only at the interface between materials rather than through the full thickness has recently been developed in TWI's Advanced Materials and Processes Group. This method results in a joint that has a greater flexibility and softer feel than is made with other joining techniques. Fabrics are most commonly joined using stitching. There are therefore a number of situations where a welding process would be more suitable, for example, leak proof seams in personal protective clothing, containment bags and tents.

Weld between blue and yellow nylon fabrics showing region of fused material in the centre and unmelted fibres on the outer surfaces
Weld between blue and yellow nylon fabrics showing region of fused material in the centre and unmelted fibres on the outer surfaces

Most welding processes for fabrics apply energy to the outer surfaces of the material (heat sealing) or to the bulk material (dielectric welding). These melt most of the thickness of the material to effect a seal, and hence stiffen the seam. A more flexible welding solution uses Clearweld TM to apply a well controlled amount of heat, just to the contacting surfaces of the fabrics. This selective heating is possible by adding a low visibility laser absorbing medium onto one or both fabric surfaces. Benefits of this process include:

  • Seam flexibility, by control of melt volume
  • Seams sealed in one operation, avoiding use of tapes
  • Potential for high speed seaming and automation
  • New design opportunities - curved seams, novel features.

To date the ClearWeld TM process has been applied to pure synthetic fabrics, blends of synthetic and natural fibres and to waterproof laminates. The ClearWeld process was invented, and is the subject of a patent application, by TWI. It is being commercialised by Gentex Corporation. The process uses lasers that are commercially available, and infrared absorbing welding consumables that are currently under development, but the intention is to create a product line of consumables compatible with commercially available delivery systems (e.g. inkjet inks, inks for liquid dispensing systems, thin films etc).

For more information, please contact us.

For more information please email:


contactus@twi.co.uk