Synergetic Etching On Polymer Materials By Atmospheric Plasma And Its Mechanism

Atmospheric pressure plasma has wide applications in the surface modification of polymer materials,because it can work continuously without any vacuum system and is an environmental-friendly technique.As an important polymer,polyethylene terephthalate(PET)and its film and fiber products are used in many fields.However,in the productive process,traditional chemical alkali hydrolysis is a widely used surface modification technology and is harmful to the environment.So,the study of alternative atmospheric pressure plasma technique is significant.In this paper,the surface modification of PET materials by atmospheric plasma is systematically investigated.A uniform surface physics and chemical etching effects on the film and fiber was obtained.A self-designed and fabricated equipment of atmospheric dielectric barrier discharges(DBDs)was used for the fiber surface modification.By adjusting and optimizing the equipment and parameters,a uniform and stable microplasma discharge was achieved.The optical emission spectrum showed that the hydroxyl,oxygen atomic and other active groups were presented in the plasma.In addition,pH value of the surface of the substrate treated by plasma was 3-4,but this value increases with time.PET fiber was etched by plasma and then by alkali for improving the etching effects.Three treatment programs(only plasma treatment,only alkali treatment,plasma and alkali combined treatments)were used for comparison.A more obvious etching effect could be obtained by the combined treatment as shown by scanning electronic microscope(SEM)observation and the fiber surface became more hydrophilic.The PET fiber had a softer luster and more comfortable handle after the combined treatment,suggesting that the combined treatment has improving synergetic etching effect.To discuss the mechanism of the synergetic effect,an experimental study of surface modification on polyethylene terephthalate(PET)film is carried out.The physics and chemical effect in the treatment process were also analyzed.A unifonn and stable plasma can be seen by the discharge and the optical emission spectrum.The atomic force microscope(AFM),micro-Raman and X-ray photoelectron spectroscopy(XPS)results showed that the plasma can greatly increase the surface roughness as well as change the chemical composition of PET films.Difference etching effects in the two different areas were also observed.Further investigation of the fundamental process and the mechanism of synergetic effect were done.It is shown that the synergetic effect was a composite process of physical diffusion and chemical adsorption of alkali.With plasma treatment,the alkali solution could diffuse more faster through the pits and craters of the fiber surface.At the same time,the polar groups in the fiber surface could adsorb more hydroxyl groups.Moreover,the motion of fiber macromolecule could also affect the synergetic results,while the motion was influenced with alkali and plasma treatment effect.In conclusion,surface modification of PET fiber by synergetic etching of atmospheric plasma and alkali treatment was carried out in this dissertation.The mechanism of the synergetic etching was provided and discussed for the first time.This improved synergetic etching method by combined atmospheric plasma and alkali treatment has great potential applications for replacing the alkali surface modification treatment.