Heat Sealing Teflonbelts

There are different types of Teflon belts, but there is no ”one procedure”  for joining their ends together that applies for all types. Different types of Teflon belts come in different thicknesses, commonly raging from 0.200 to 0.300 mm. As a general rule, the greater the thickness is of the belt and its bonding material, the greater the time and temperature must be.  

Two types of bonding materials are commonly used for sealing Teflon belts, PFA and PTFE materials. Bonding materials are, like belts, available in different widths and thicknesses.
PTFE bonding materials, like thread sealing tape, requires a much greater amount (time, temperature) of heat.

Heat Sealing Unit

Use a digital thermometer with surface probe to measure the real temperature of the heated base and compare it to the Set Point and displayed on the Heat Sealing Unit. Do these values agree? If not, correct the displayed temperature, or take note of the difference. A real temperature of the base which is 10°C lower than displayed, will produce a significantly weaker seal. A lower than expected temperature on the heated base, is a common cause when belts split at the seal.  

Finding Parameters

Arrange 2 smaller pieces of Teflon belts for trail purpose in the fixture which is used to hold the ends in place. The pieces shall be wide enough to house 3 separate seals with ca 30 mm space between them. The pieces and the bonding material used for the trail shall be of same type, material, width and thickness as used on the cooking system.

 Align the pieces in the fixture. The overlap shall be the same as the width of the bonding material. Use latex gloves or be careful not to contaminate the surfaces. Clean surfaces with alcohol or degrease if they become contaminated with fingerprints or filth. Apply the bonding material between the two pieces and use tape to fix their ends. Make 3 separate seals ca 30 mm apart. 

When using PFA-tape as bonding material, apply the first seal at 380°C for 1 minute, second at 390°C for 2 minutes and third at 400°C for 3 minutes. With a cloth or paper, press and rub the hot seal to remove air and smoothen the seal right after the heated base is removed. Repeat the procedure for all seals. Allow the seals to cool for 3 to 5 minutes before proceeding. 

When PTFE is used as bonding material, apply the first seal at 390°C for 3 minutes, the second at 390°C for 5 minutes and the third at 400°C for 5 minutes. Allow the seals to cool for 3 to 5 minutes before proceeding. 

Split Test

Once cooled, pull the seals apart using tongs or nippers. Look for a seal where the belts Teflon coating and the bonding material are married and pulled the Teflon coating off the glass fibre core, exposing its white fibres. That is the result you are looking for!