Characterization of the laser bonding of a linear low density polyethylene film to a polypropylene substrate

This work investigates the effectiveness of using a 10.6 μm CO₂ marking laser to activate a thermally sensitive adhesive coating on linear low density polyethylene film for the purpose of bonding the film to polypropylene substrate. A potential technical hurdle in the form bubbling has been witnessed and described. Bubbling prevented contact between the two laminates and impinged upon the viability of the bonds produced; film handling improvement is recommended as a solution. The Gaussian profile of the laser in concert with the circular laser spot shape and the traverse strategy of the scans used caused the centre of the bond to be over irradiated whilst the edge was under-irradiated. This had several affects: it limited the area over which an effective bond was achieved; caused delamination of the film at the track edges and locally modified the polypropylene structure. A highly consistent and repeatable mean peel resistance force of 1.09 N was achieved using the laser activated adhesive bonding technique described. Little bond strength dependency upon laser irradiance was observed, which allied with the results of other work, leads to the proposal that the adhesive has a very broad laser irradiance operating range.