Influence of pore size on penetration of surface modification into woven fabric treated with atmospheric pressure plasma jet

One of the biggest difference between atmospheric pressure plasma jet (APPJ) and other plasma surface treatment is that only one side (top) of substrate is contacted with plasma jet at atmospheric pressure while in other plasmas two sides (top and bottom) of substrate are both contacted with plasma. The modification of the bottom side of woven fabric treated by APPJ is largely dependent on the penetration of active species in plasma jet, which is accordingly affected by plasma parameters and the structure of materials. In order to investigate the influence of pore size on penetration of surface modification into woven fabric treated with APPJ, four kinds of polyester woven fabrics with different pore sizes were used as the model porous medium. Two groups of parallel polyester fibers are respectively and tightly pasted on the top and bottom side of each fabric. Penetration of plasma effects through the pores was detected by changes in contact angle on the bottom side before and after APPJ treatment. It was further demonstrated by changes in surface morphology and chemical composition using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analyses. The degree of penetration of APPJ surface modification was increased with the increasing pore size. Complete penetration was realized in fabric with pore size larger than 200 mu m and nearly no penetration was found in fabric with the pore size smaller than 10 mu m. This is attributed to more active species in plasma jet diffusing through the larger pores in fabric. Those species can reach the bottom side without losing their modifying ability during the movement process. Therefore the pore size might be a more important factor affecting penetration of APPJ surface modification into woven fabric. (C) 2010 Elsevier B.V. All rights reserved.