A novel CO₂ laser welding of plastics using a transparent solid heat sink without causing thermal damage

The paper introduces a novel concept of CO2 laser welding of thermoplastics which is applicable to manufacturing medical appliances, micro-scale devices and the products requiring the smooth surfaces of welded region. The procedure has a few features: (1) to place a solid heat sink transparent to a infrared radiation beam in contact with an irradiated plastic to cool the surface during welding process, (2) to use no pigmentation or dye for radiation absorption enhancement, (3) to sustain thermal damage on the surface, and (4) to avoid the emission of harmful gas due to decomposition of plastics. The feasibility of the welding procedure for natural transparent plastics such as polyolefin and perfluoroalkoxy resins without any surface damage was examined using a CO2 laser as a radiation source with a solid heat sink. The experiments for overlapped films welding as well as tubes welding were conducted by means of the CO2 laser. The heat transfer analyses in the welding process were also carried out to obtain the temperature profiles in the plastics during the welding process.