Comparison between Joining Technologies for Polymeric Films

Abstract

The packaging industry makes extensive use of thermoplastic polymers in film format that can have a thickness of less than 100 microns. Joining such thin films requires a tight control of several process parameters and of material homogeneity. Among the available technologies, heat sealing is widely applied along with solvent based gluing that is the more traditional technique.In this paper, welds of thin polymeric films have been produced by means of a solid-state Laser source and the solvent based technique with the aim to compare their performances. Thin films specimens were cut from commercial rolls used in labelling applications or prepared from purposely-designed polymer blends by compression between the heated plates of a laboratory press. Blends prepared in laboratory using poly(lactic acid) or poly(lactide) blended with different percentage of an impact modifier were designed to test the sealing properties under laser welding irradiation respect to solvent bonding.The solid-state laser source allows a short process time without direct contact between tool and part and thus without contamination of the film. Solvent gluing tests, by dispersing a controlled amount of solvent with a micro syringe by hand, were carried out. The material was characterized by means of differential scanning calorimetry, DSC. Changes along the welded lines by laser radiation and solvent gluing were characterized by micro FTIR and micro Raman techniques. An Instron 5966 testing machine, in the tensile mode, was used for measuring the strengths of the bonded films.