Welding PFA

PFA tubes and pipe liners can be butt-welded in a similar procedure to that used for PTFE (Sec. 7.4.2). PFA does not require adhesive to form a bond. PFA is easily welded by a heated platen technique in which the liner ends contact the heated plate until a bead is formed. A heater plate temperature of 399°C, a contact time of 15-30 secs, and a soak time of 90-105 secs are required for liners with a diameter of 2.5- 

P l Soak time is the time period allowed after the bead has been formed. No pressure is applied 

Amorphous plastics, such as acrylics, are transparent to infrared rays. Some semiciystalline polymers, such as PFA, have surprisingly high levels of infrared transmission. PFA can be welded by infrared under certain circumstances. For example, a transparent tube of PFA was welded to a black sheet of PFA that absorbed the infrared light generated by aNd YAG laser (1,064 nm).P8] a tube composed of natural PFA (6.4 mm outer diameter and 3.2 mm inner diameter) was pressed into a 6.4 mm diameter hole in an aluminum sheet. The aluminum sheet was used to shield the black PFA sheet from stray radiation. The IR light was defocused to a diameter of 6.4 mm and aimed at the end of the tube in the aluminum. A laser power of 30 W with a tube length of 50 mm produced a strong weld in a few seconds. 

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