Surface studies by attenuated total reflection spectroscopy. I. Corona treatment of polypropylene

Abstract

The chemical changes produced by brief corona treatments of polypropylene films have been studied by attenuated total reflection (a.t.r.) infrared spectroscopy. Surface layers of different thicknesses were investigated by varying the reflection conditions. Changes in the surface spectra were quantitatively compared by the use of an internal correction method which compensated for irreproducible experimental conditions. Corona treatment in a nitrogen atmosphere produced thin surface layers (less than 500 A) of C-C unsaturation. Nitrogen derivatives were not detected in the surface. Corona treatment in oxygen caused surface changes which depended markedly on the corona conditions owing to the generation of ozone in the discharge zone. At low ozone concentrations, both unsaturation and oxidation were found in surface layers of under 500A thickness. At higher ozone concentrations, extensive oxidation occurred at appreciable depths into the polymer (several microns). An oxygen corona appears to result in essentially the same surface changes as does a nitrogen corona treatment, followed by exposure to ozone.

Thermally stimulated discharge current studies of corona polarized pristine and swift heavy ion irradiated kapton-H polyimide

“…0.55 and 1.05 eV, respectively. The presence of these current maxima in normal current direction is in confirmity with its thermo-electret behavior [4,17,24].…”

“…According to Carlson and Willes [17], a high field established by corona in its proximity causes local air ionization. Corona ions impinging on the polymer surface exchange charge with surface atoms.…”

The Use of Primers in Bonding Polypropylene

“…The surface treatments used on polymers have been reviewed by Briggs [1] and WU [2], while detailed reports have been published on the use of flames [3,4], chromic acid [5,6], permanganate [7] and electric discharges [8,9,10]. Essentially all these treatments attack the surface of polypropylene and replace C-H bonds by C-O, either as carbonyl or hydroxyl functions.…”

Corona Treatment of Polymeric Films

“…Recommended treatment levels for polyolefins are 3-4 wattsminutes/sq ft, although much higher levels are sometimes necessary for good adhesion [2]. These excited molecules dissociate to form free radicals, ions and photons [1,[3][4][5][6]. Highly reactive oxygen fragments can in turn react with oxygen molecules to produce ozone.…”

“…Previous studies [12] have supported the hydrogen bonding theory as the primary reason for enhancement of film adhesion characteristics through corona treatment. Corona treatment of polyethylene in an inert atmosphere cannot produce oxygenated functional groups, but studies indicate that good self-film adhesion, as well as ink adhesion to the film, is obtained [5,13]. Polyethylene, treated in a pure nitrogen corona, formed basic functional groups which adsorbed acidic, but not basic, dyes.…”