Laser welding of carbon fibre filled polytetra fluoroethylene

Herein, a method is described to weld polytetrafluoroethylene (PTFE), a non-melt processable thermoplast, using a thulium laser. Different settings for laser power and speed were used. The resulting mean lap shear strength per setting ranged from 0.081 N/mm(2) to 0.297 N/mm(2). The optimal setting was found to be 12 W irrespective of the welding speed applied. Micro-computed tomography (mu-CT) and optical microscopy was used to show that the welded pattern consisted of tunnel defects. As PTFE is known to be non-melt processable, a physico-chemical characterization was performed to examine the formation of degradation products. Differential scanning calorimetry (DSC) showed a reduction in molecular weight of the PTFE in the weld pattern after welding. Attenuated total reflectance infrared (ATR-IR) and nuclear magnetic resonance (NMR) spectroscopy using hexafluoroisopropanol (HFIP) did not indicate the presence of any new compounds in the respective spectra.