Abstract
We studied the epoxy polymer surface modification using air plasma treatment in a Gliding Arc (GA) plasma reactor and a pulsed Dielectric Barrier Discharge (DBD). We employed optical emission spectroscopy (OES) measurements to approximate the vibrational and rotational temperatures for both plasma sources, as well as surface temperature measurements with fiber optics and IR thermography to corelate with the corresponding hydrophilization of the epoxy material. Water contact angle measurements revealed a rapid hydrophilization for both plasma sources, with a slightly more pronounced effect for the air DBD treatment. Ageing studies revealed stable hydrophilicity, with water contact angle saturating at values lower than 50°, corresponding to a >50% decrease compared to the untreated epoxy polymer. ATR-FTIR spectroscopy studies showed an additional absorption band assigned to carbonyl group, with its peak intensity being higher for the DBD treated surfaces. The spectra were also correlated with the surface functionalization via the relative peak area ratio of carbonyl to oxirane and benzene related bands. According to SEM imaging, GA plasma treatment led to no apparent morphological change, contrary to DBD treatment, which resulted in nano-roughness formation. The enhanced surface oxidation as well as the nano-roughness formation on epoxy surface with the air DBD treatment were found to be responsible for the stable hydrophilization.
Highlights
The optical emission spectroscopy (OES) experiments for the Dielectric Barrier Discharge (DBD) plasma were performed along the horizontal axis in the 2 mm gap between the high voltage (HV) electrode and the epoxy surface
The time dynamic of hydrophilization maintenance seems similar between the two plasma treatments, even if the air DBD treatment leads to slightly lower stabilized contact angles compared to Gliding Arc
We have studied the epoxy polymer surface modification a Gliding
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Contrary to the vast literature in thermoplastic materials (mostly polyolefins), only a few works have reported on atmospheric pressure plasma treatments of epoxy-based materials. Some of those studies focus on the hydrophobic treatments of epoxy resin to enhance its insulation performance [28,29]. The air DBD plasma treatment has emerged as a promising means of epoxy surface modification, the study of other air-based plasma sources like Gliding Arcs has hardly been explored. We studied the surface modification of epoxy resin using Gliding Arc discharges in dry air and we showed the potential for rapid hydrophilization [35]. We investigate the water contact angle (WCA) evolution and stability, and we apply Fourier transform infrared (FTIR) analysis and scanning electron microscopy (SEM) to record the effect of the different plasma treatments on the epoxy surface chemistry and morphology, respectively
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