Ultraviolet and Infrared Femtosecond Laser Irradiation of Thermoplastics PET and PA66Wednesday (24.06.2020) 13:40 - 13:43 Room 1
Polyethylene terephthalate (PET) and Polyamide66 (PA66, or Nylon) are important thermoplastic polymers ubiquitous in all walks of life. Depending on their applications, various surface functionalities are desired to enhance their performance, such as reduced friction coefficient, self-cleaning, anti-fouling etc. One of the possible ways to render a surface with above mentioned functionalities is through ultrafast laser surface patterning [1-2]. In order to assess the viability of surface patterning by ultrafast laser, a comparative study was carried out to investigate the nature of the interactions between the polymers of interest and femtosecond laser pulses, in Infrared (IR) wavelength and Ultraviolet wavelength regimes. Two laser sources were deployed, one at 800 nm wavelength with a pulse duration of 60 femtosecond (fs), and the other at 257 nm with a pulse duration of 190 fs, with the former prone to non-linear surface interaction, and the later for direct bond-breaking reactions. The ablation thresholds for two polymers were extrapolated for 800 nm and 257 nm conditions. The ablation morphologies were evaluated. And surface chemical states were characterized.
It turns out that the interaction depends strongly on laser wavelengths, as well as laser beam intensity profile on the sample, and irradiation conditions (laser energy, the number of pulses, etc). Different surface morphologies and topographies were observed, closely related to UV and IR irradiation conditions. Surface chemical decomposition was observed in both UV and IR regimes, under certain irradiation conditions.
Ultrafast laser ablation of both PET and PA66 produces clean, smooth, and well-defined crater profiles (see figure 1a the upper SEM micrographs). Nonetheless, a marked surface decomposition was identified at irradiated PA66 surface (figure 1b), which is supposedly undesirable for polymer processing and surface functionalization applications. With the exception of high fluence operation conditions, ultrafast laser processing in IR does not degrade surface chemistry significantly (not shown here), but the craters are somehow rougher with splashes presented in the vicinity.
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