TWI’s Advanced Materials and Processes department has recently developed a technique for welding thermoplastic fabrics, which melts only at the interface between materials, rather than through the full thickness. This results in a joint that has a greater flexibility and softer feel than one that is made with other welding methods.
Fabrics are most commonly joined using stitching. There are, however, a number of situations where a welding process would be more suitable. Consider the requirements for leak-proof seams such as in personal protective clothing, containment bags or waterproof jackets and tents. Seam sealing compound or tape is often added to stitched seams to give a seal, which adds cost to the joining operation. The presence of holes also has the potential of weakening the fabric in the region of the seam.
Most welding processes for fabrics apply energy to the outer surface of the material (e.g. heat sealing) or to the bulk material (e.g. dielectric welding). These result in melting of the majority of the thickness of the material to effect a seal, and hence stiffen the seam.
A more flexible welding solution uses transmission laser welding (ClearWeld™ - see www.clearweld.com) to apply a well-controlled amount of heat, just to the contacting surface of the fabrics. This selective heating is achieved by introducing a low visibility laser absorbing coating onto one or both of the fabric surfaces. Resulting beneficial features of the process include: