Corona-Treated Polyethylene Films Are Macroscopic Charge Bilayers

Abstract

Top and bottom surfaces of polyethylene (PE) films exposed to corona discharge display large and opposite electrostatic potentials, forming an electric bilayer in agreement with recent and unexpected findings from Zhiqiang et al. Water wetting, chemical composition and roughness of the two surfaces are different. Surprisingly, the bottom surface, opposite to the corona electrode is charged but it is not oxidized, neither is it wetted with water. Moreover, its morphology is unaltered by charging, while the hydrophilic top surface is much rougher with protruding islands that are the result of oxidation followed by phase separation and polymer−polymer dewetting. Common liquids extract the oxidized, hydrophilic material formed at the upper surface, a result that explains the well-known sensitivity of adhesive joints made using corona-treated thermoplastics to liquids, especially water. These results show that poling the surface closer to the corona electrode triggers another but different charge build-up process at the opposite surface. The outcome is another poled PE surface showing high potential but with unchanged chemical composition, morphology and wetting behavior as the pristine surface, thus opening new possibilities for surface engineering.

Inscribing wettability gradients onto polymer substrates with different stiffness using corona discharge in point-to-plane geometry

“…During the discharge the ion flux is highest at the center of the corona-treated spot (Warburg's law). Owing to the insulating character of polymer materials the ions are trapped at the surface for a certain time [16,[37][38][39][40][41][42][43], which leads to charge accumulation in the center of the corona-treated spot. Because of charge accumulation the electric-field distribution gets modified, yielding a current density distribution that is no longer described by Warburg's law.…”

“…Among these techniques, one of the most frequently applied to reduce the hydrophobicity of polymer surfaces is based on plasma or UV-treatment [2][3][4][5][6][7][8][9][10][11][12][13]. Plasma treatment has become an important process and is widely used in industrial applications [14][15][16].…”

Single-cycle atomic force microscope force reconstruction: resolving time-dependent interactions

“…A physically relevant and important case where these hysteretic forces are believed to prevail is in the presence of capillary neck formation and rupture [54,56]. Other relevant scenarios might involve bond formation and rupture due to chemical affinity, or other, between the tip and the sample [57,58]. A simple mathematical formulation of F on-off forces is…”

Lasting high surface energy co‐polyester ionomer and its application in laminated tin‐free steel

“…However, this kind of film is difficult to be laminated on TFS due to its relatively high melting temperature and low surface energy, which greatly limits its application in the industry of polymer laminated TFS . So, BOPET film is modified by surface treatment to improve the surface energy, thermal properties, and interfacial property when it is used as laminating material instead of coating resin . Nevertheless, surface treatment is not a permanent method, as the surface effect will decline after a period of time, known as the “decaying effect.” When BOPET corona film is exposed to humid, hot air for some time, its hydrophilicity will decline evidently and even return to the level of untreated state.…”

“…10,11 So, BOPET film is modified by surface treatment to improve the surface energy, thermal properties, and interfacial property when it is used as laminating material instead of coating resin. [12][13][14][15][16] Nevertheless, surface treatment is not a permanent method, as the surface effect will decline after a period of time, known as the "decaying effect." [17][18][19] When BOPET corona film is exposed to humid, hot air for some time, its hydrophilicity will decline evidently and even return to the level of untreated state.…”