Gas-tight thermally joined metal-thermoplastic connections by pulsed laser surface pre-treatment

Thermal joining of laser-structured metals and thermoplastics has been proven to deliver a high joint strength. A novel idea is to apply this process onto metal-thermoplastic joints in order to produce gas-tight hybrid connections which can be used in several technical applications. The surface pre-treatment of aluminum by infrared pulsed laser radiation was focused in this study. Depending on different cumulative energies two main surface topologies, stochastic and deterministic groove structures, were manufactured. Consequently, heat conduction joining by infrared laser radiation was used to join the metal with polypropylene. The influence of laser structuring on surface roughness and groove geometry was analyzed by scanning electron and laser scanning microscopy. The wetting of the thermoplastic was investigated by optical microscopy. The gas-tightness was identified by a helium leak test and climate testing was performed to analyze the long-term durability. The results indicate that depending on the surface morphology of the metal, durable gas-tight connections can be created by thermal joining.