Desmopan® and Texin™ components can be joined together by welding. Suitable methods include:
- Hot air and nitrogen welding
- Hot plate welding
- Heated tool and heat impulse welding
- High-frequency welding
- Friction welding
- Vibration welding
In all cases, an efficient extractor must be provided for any carbonization gases.
Hot air and nitrogen welding
When welding with hot air or hot nitrogen, the flow of gas (measured 1 cm in front of the nozzle) should have a temperature of 290 - 330 °C. To increase the weld strength, it is advisable to solidify the plastic weld with a cooled pressure roller.
Hot plate welding
Hot plate welding is particularly useful for the butt-welding of profiles. Both surfaces are melted on plates heated to 290 - 330 °C and joined together under pressure so as to produce a bead. This bead can, if necessary, be machined off after cooling.
Heated tool and heat impulse welding
The heated tool and heat impulse welding methods are suitable primarily for thin-walled articles and fi lm. Care must be taken with these processes that suffi cient pressure is exerted on the two parts being joined until the weld has cooled.
Desmopan® and Texin™ can be joined very well indeed by high-frequency welding.
1 mm thick film can be welded perfectly on a 2 kW unit, and a weld strength of 70 - 95 % of the material’s strength is achieved.
Even with film of 2 mm thickness, the weld strength is still 40 - 60 %. The higher strength applies to soft Desmopan® and Texin™ grades and the lower one to hard grades.
Axially symmetrical parts of Desmopan® or Texin™ can be joined together by friction welding. With suitable apparatus, this process can also be used on the production line. Depending on the nature of the component and the holding device, the mean peripheral velocity of the rotating half of the component should be 300 - 500 m/min. The faces of the parts being welded should be melted so that a bead becomes visible on pressing them together. The resultant loss of length must be established in preliminary trials and taken into account when dimensioning the component.
Vibration welding is useful in cases where friction welding is unsuitable because of the shape of the article. It enables large parts of differing geometries to be welded securely to each other. Vibration welding can be used for parts to be joined either at an angle or straight.
This welding technique is not recommended because of the high inherent damping of TPU. The strength of the welds is lower than with the other welding processes.