Principles of Seam Sealing

When seam tape is heated up, the adhesive on the tape is activated. This activated tape is applied on the water proof coating or lamination of the fabric seam under pressure. When cooled, a strong bond is formed between the tape and the seam. This bond is so strong that it will prevent pressurized water from penetrating the sewn seam. As a result, a water proof seam is produced.

A hot air machine produces hot air with precisely controlled temperature to directly heat up the adhesive of seam tape. The heated tape and the fabric are feeding into two oppositely rotating rollers under pressure called nip rollers. The linear speed of the nip rollers is called sealing speed.

During sealing, hot air is being blown out from the nozzle. The hot air that actually reaches the surface of the tape is a mixture of hot air from the nozzle and surrounding air, hence the actual temperature that appeared on the tape is somewhat lower than the nozzle temperature. The farther the distance between the nozzle and the tape, the higher the percentage of surrounding air becomes. On the other hand, a higher hot air flow rate will reduce the percentage of surrounding air causing the hot air temperature appeared on the tape to be higher. So both the nozzle position and hot air flow rate are very important factors.

So, the major factors that can affect the seam sealing are as follows:

• Hot air temperature
• Sealing speed
• Nozzle air pressure
• Air flow rate
• Nozzle position

When a consistent product is required, the combination of the above factors have to be set precisely as their effects towards a proper sealing are all interconnecting.