Graft Polymerization of Acrylic Acid onto Polypropylene Monofilament by RF Plasma

Plasma-induced graft polymerization of acrylic acid onto polypropylene monofilament was carried out to introduce carboxyl groups on its surface. The monofilament was treated with oxygen plasma to create hydroperoxide groups and subsequent graft polymerization of acrylic acid on exposed filament was carried out. An increase in the plasma power led to higher graft levels. It was observed that the hydroperoxide build up on PP surface follows linear increase with the increase in the plasma treatment time only up to 180 s beyond which it slowed down significantly. The formation of oxygenated species was ascertained by X-ray photoelectron spectroscopy, and the peroxide content was measured by the 2'-diphenylpicrylhydrazyl (DPPH) estimation. The grafting was observed to be considerably influenced by the plasma exposure time, plasma power, reaction temperature, mono-mer concentration and the storage temperature. A maximum in the degree of grafting was observed at 40% monomer concentration beyond which grafting tended to decrease very fast. The grafting was also found to be maximum at 50 degrees C followed by a sharp decrease, subsequently. The storage of the exposed filament at -80 degrees C led to the identical grafting all along the 16 days. However, the storage at 25 degrees C showed significant reduction in the degree of grafting. The atomic force microscopy showed that surface morphology is transformed into a nonhomogeneous one after the plasma exposure, but tends to flatten out after the grafting process in the form of globular structures. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2884-2892, 2010