Physical properties of plastic joints welded by Diode Laser

The Thermal Laser Welding (TLW) process involves localized heating at the interface of two pieces of plastic that will be joined. Polymeric materials of Ultra High Molecular Weight Polyethylene (UHMWPE, GUR 1020 biomedical type), both pure and containing nanostructures at different concentrations (carbon, titanium and silver nano-particles), were prepared as thin foils in order to produce an interface between a transparent substrate (to the infrared laser wavelength) and an highly absorbent substrate to be welded by the laser irradiation. The used diode laser operates at 970 nm wavelength, in continuum, with a maximum energy of 100 mJ, for times of the order of 1-60 s, and uses a spot of about 1 mm2. The properties of the polymers before and after the laser welding process were measured in terms of optical characteristics, wetting ability of biocompatible solutions, surface roughness, surface morphology and surface composition. Mechanical features of the surface has been also studied in order to check the changes induced in the polymeric joint by the laser welding energy.