Welding of polymers using a 2μm thulium fiber laser

Absorber-free transmission and butt-welding of different polymers were performed using thulium fiber laser radiation at the wavelength 2μm. The relations between the laser process conditions and the dimensions and quality of the seam were investigated by means of optical and phase-contrast microscopy. Mechanical properties of the weld joints were studied in tensile strength tests. Laser-welded polyethylene samples revealed a tensile strength of greater than 80% of the bulk material strength. Transmission welding of different polymer combinations featured the formation of different joint classes depending on the spectral properties. The experiments demonstrate new application areas of mid-IR fiber laser sources for materials processing. ► We performed absorber-free transmission and butt-welding of different polymers using mid-IR fiber laser radiation. ► Laser-welded polyethylene samples revealed a tensile strength of greater than 80% of the bulk material strength. ► Transmission welding of polymer combinations showed the formation of different joint classes. ► Experiments demonstrate new application areas of mid-IR fiber laser sources for materials processing.