Laser-Marking Mechanism of Thermoplastic Polyurethane/Bi2O3 Composites
2015
Zhong, Wei | Cao, Zheng | Qiu, Pengfei | Wu, Dun | Liu, Chunlin | Li, Huili | Zhu, He
Using bismuth oxide (Bi₂O₃) as a laser-marking additive and thermoplastic polyurethane (TPU) as the matrix, TPU/Bi₂O₃ composite materials were prepared by melt blending in a torque rheometer. The sheet samples prepared from the TPU/Bi₂O₃ composites were treated in air by scanning with a neodymium-doped yttrium aluminum garnet (Nd: YAG) pulsed laser beam at a wavelength of 1064 nm. Compared with the pure TPU sample, the laser-marked composite samples exhibited differences in marking contrast as the Bi₂O₃ content increased from 0.1% to 1.0% based on stereomicroscope analysis. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetry analysis, and X-ray diffraction were used to characterize the laser-marked surface material of the composite samples. Furthermore, a mechanism for the laser-effected darkening of the TPU/Bi₂O₃ composites was proposed. The results herein indicated that the addition of the Bi₂O₃ laser-sensitive additive to TPU resulted in laser darkening of the TPU/Bi₂O₃ composites. The marking contrast and visual appearance of the surface of the TPU/Bi₂O₃ composites after laser irradiation was due to a synergistic effect consisting of carbonization via TPU pyrolysis and reduction of Bi₂O₃ to black bismuth metal.
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