Modification of surface properties of polyamide 6 films with atmospheric pressure plasma
Research highlights
► We treated polyamide 6 films using pure helium (He), He/O2 and He/CF4, respectively. ► We investigated the effect of the different plasma gases treatment on the surface modification of atmospheric pressure plasma. ► The addition of O2 or CF4 to He plasma had different effectiveness on the polymer surface modification.
Introduction
Plasma treatment has been utilized widely in polymer surface modification in the recent years. It is an effective way to modify the properties of the polymer surface without affecting the bulk properties [1], [2], [3]. Plasma treatment has been studied and proved to be an advancing method for providing the polymer surface hydrophilicity to improve wetting, dyeing, printing and adhesion properties [4], [5], [6]. Under the bombardment of active species generated by a homogeneous plasma, a polymer surface can be changed by removal of surface contaminations [7], [8], introduction of new chemical functional groups [9], [10], [11], [12], [13], [14] or deposition of a thin coating [15], [16], [17]. However, most of the plasma systems require an expensive and complicated vacuum environment [18]. Atmospheric pressure plasma devices have been developed to overcome the drawbacks of low pressure plasma treatment in which a vacuum system is required. In recent years, an atmospheric pressure plasma jet (APPJ) is invented to produce the homogeneous plasma at low temperature [19], [20].
The purpose of this study is to investigate different plasma gases affect the plasma etching rate of polyamide 6 films using atmospheric pressure plasma jet. The surface wetting properties were evaluated by measuring the water contact angle using the sessile drop method and the surface morphology and chemical changes were examined by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The etching rate was also studied after plasma treatment and the T-peel strength of the plasma treated and control films was carried out to show the surface adhesion properties of the films.
Section snippets
Material
The sample material studied here was commercial low density polyamide 6 films with a density of 1.134 g/cm3. The films were cut into 2 cm × 5 cm specimens. To remove finishes or surface contamination, the specimens were soaked in acetone for 10 min and then dried in a desiccator for 24 h at room temperature.
Plasma treatment
The specimens were treated on an atmospheric pressure plasma jet (APPJ) apparatus (Atomflo-250, Surfx Company, USA) with pure He (flow rate: 20 L/min), He/O2 (flow rate: 20/0.2 L/min) and He/CF4
Contact angle measurement
The surface properties of polyamide 6 films were analyzed by contact angle measurement. To evaluate the effect of different plasma gases modification, polyamide 6 films were treated with different plasma gases. Table 1 shows that the variation in contact angles of the treated polyamide 6 film surfaces as a function of different plasma gases. Table 1 shows that contact angle of the control is 76°. It is found that there is a decrease in the surface contact angle from 58°, 29° and 25° when the
Conclusions
The atmospheric pressure plasma treated polyamide 6 films showed increased surface roughness, increased surface oxygen or fluorine contents and hydrophilic polar groups, leading to lower water contact angles, and improved T-peel strength than the control. When the O2 or CF4 added into helium, all above favorable effects are further enhanced. Plasma etching rate is promoted as the O2 or CF4 added into helium plasma gas. He/CF4 plasma has the highest bonding strength for the same duration of
Acknowledgements
This work was supported by the National High Technology Research and Development Program of China (no. 2007AA03Z101), Natural Science Foundation for the Youth (no. 50803010).
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