Laser transmission welding of Clearweld-coated polyethylene glycol terephthalate by incremental scanning technique

• A TWIST mode was adopted to weld PET in comparison with traditional welding mode.
• Influence of laser parameters at TWIST mode on the quality of weld seam was studied.
• Morphology of the weld seams was analyzed to understand the welding mechanism.
• The weld seams obtained by two modes have nearly same shear strength and sealability.
• The weld seams obtained by TWIST have shallow HAZ depth and uniform HAZ distribution.

Transmission laser welding using Incremental Scanning Technique(TWIST) mode and conventional contour welding mode were adopted to investigate laser transmission welding of 0.5 mm thick PET plate. A 1064 nm fiber laser was used to weld PET at the (TWIST) mode, and an 808 nm diode laser was applied to conduct the conventional contour welding. The Clearweld coating was used as laser absorbing material. The influences of laser parameters (i.e. defocusing distance, distance between two circles) on the quality of weld seams were analyzed by optical microscopy. Moreover, geometry and shear strength of the weld zone were tested to optimize laser parameters. Additionally, the water vapor permeability (WVP) of weld seams was measured to test hermetical capacity. Results show that the shear strength and hermetic capacity of weld seam by TWIST mode are at the same level in comparison with that of the conventional contour welding.