Effect of carbon black on light transmission in laser welding of thermoplastics

It is important to describe the laser energy transmission and absorption in polymers properly when modeling heat transfer in laser transmission welding (LTW) of thermoplastics. This paper uses the Bouguer–Lambert law and an apparent absorption coefficient to describe the total laser energy attenuation in scattering polymers with and without carbon black (CB). The model was validated using the measured transmittances as a function of part thickness for unreinforced polyamide 6 (PA6), glass fibre reinforced polyamide 6 (PA6GF) as well as amorphous polycarbonate (PC). A linear relationship between the (apparent) absorption coefficient and the CB level in polymers was observed experimentally for PA6, PA6GF and PC.