Laser Transmission Welding On Medical Plastics:Processing Parameters And Properties

Laser transmission welding of plastic has been researched in recent years, however, considering about the high transmittance of thermoplastics in conventional wavelength range(400-1100nm), a light-to-heat conversion interface layer is required for forming a fusion weld joint at interface. Hence, the laser absorption of material is an important issue in the application in medical industry.In this paper, two welding modes have been used to solve this problem. First, transmission laser welding using Incremental Scanning Technique(TWIST) mode and the Clearweld coating were adopted to investigate laser transmission welding by a laser with 1064 nm wavelength, and then applied in medical industry; second, a new wavelength laser(?=1940nm) was adopted to weld plastic without additive, and then applied in medical industry. Dino-capture was used to observe and analyze the influence of process parameters on macro morphology and heat affect zone of low density polyethylene(LDPE) and polyethylene terephthalate(PET) weld seam. Shear strength of weld seam was tested to analyze the impact of weld mode on the quality of the weld seam. Additionally, the water vapor permeability(WVP) of weld seams was measured to test hermetical capacity.The shape of the heat affect zone(HAZ) at TWIST mode is characterized by bone-like appearance rather than ellipse-like appearance obtained by conventional contour welding, and with narrower HAZ and much more uniform welded zone. The weld seam obtained by new wavelength laser have a full penetration HAZ, and The depth of the weld seam obtained by two new mode increase with the higher power and lower welding velocity. The shear strength of the PET weld seam changes little at conventional contour welding and new wavelength laser welding, while the shear strength of PET weld seam decreases with the increase of the welding speed at TWIST mode. The shear strength of LDPE weld seam decreases with the increase of the weld seam at three modes. Moreover, the shear strength and hermetic capacity of PET weld seam by TWIST mode are at the same level in comparison with that of the conventional contour welding and new wavelength laser welding, while the shear strength of the LDPE weld seam obtained by new wavelength is higher than the other two modes regardless of the bad surface quality.