Comparison of the efficiency of N sub 2 and NH sub 3 plasma treatments to improve the adhesion of PP films to in situ deposited aluminum coatings. Study of ageing phenomena in terms of acid-base properties

• Published in: International journal of adhesion and adhesives 1995-07, Vol.15 (3), p.177-184
• Main Authors: Arefi-Khonsari, F, Tatoulian, M, Shahidzadeh-Ahmadi, N, Amouroux, J
• Format: Article
• Language: English
• ISSN: 0143-7496

The paper reports on the characteristics of polypropylene (PP) treated at two different frequencies, 70 kHz and 13.56 MHz, in a two plasma atmosphere, NH sub 3 and N sub 2 plasmas. Chemical modifications created on the plasma-treated material were investigated by different complementary surface analytical techniques (x-ray photoelectron spectroscopy, XPS and contact angle measurements), which revealed a higher reactivity of the NH sub 3 plasma. The incorporation of nitrogen plays an important role as revealed by the adhesion study of thermally evaporated aluminium with treated PP: the measured peel strengths were two times higher for NH sub 3 -treated surfaces than for N sub 2 -treated ones, with XPS measurements showing a sharper increase of N/C ratio as a function of treatment time for the former treatment. Aging of the PP pretreated in NH sub 3 was also studied in terms of surface acid-base properties. The work of adhesion, calculated from contatct angle measurements, showed a distinct dependence on the pH value of the test liquids and good correlations were obtained with peel test results. The basic character of the NH sub 3 -treated PP disappears with aging, leading to an amphoteric surface.