Surface treatment of polymers for adhesive bonding

Abstract

spopsisFurther studies of a new and highly effective method for the surface treatment of low surface energy polymers for adhesive bonding are reported. Mechanisms are suggested for the increase in the cohesive strength in the surface region of polyethylene when it is exposed to activated species of inert gases. The technique is unique because, in contrast with results obtained with other methods, bulk properties of the polymer such as color or tensile strength and elongation are unaffected and surface properties such as wettability and dielectric properties such as surface conductivity are essentially unchanged.

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

“…theory, since the electrical field amplitude can be assumed to be constant across this thin layer (thickness d) (5). The O.D.,-, value for a single reflection will then be given by substituting the values of (Ic, for the thin layer case, expression [4], in expression [2]. The O.D.,,,, value will, however, begiven by substituting the values of (Ic for an infinite substrate, expression [3], in expression [2].…”

“…Kd \ value leads to a [ C-C/ of 5 M after a 100 s / -\I corona. Based on the gel content, the surface film thickness produced by glow discharge treatment of polyethylene in inert gases (Hz, He, and Ne) has been estimated to range from 300 A (1 s exposure) to 2000 A (100 s exposure) and to be independent of the nature of the gas (2). It may seem paradoxical that thin surface layers (possibly less than 100 A) can be studied in the presence of surface irregularities, such as occasional calendering marks, which may be as great as 1000 A in depth.…”

“…f r o m excited g a s molecules t o t h e polymer surface (2). This transfer was proposed to generate H a t o m s which diffused into t h e polymer a n d caused the observed penetration of t h e glow discharge effect ( u p t o l o 4 A).…”

“…Some glow discharge treatments (i.e. plasma at about 2.0-0.2 Torr) improve the adhesive bonding properties of polyethylene surfaces (2,3). The nature of the chemical and physical changes which occur during various types of plasma treatment of polyolefins has not yet been fully established, although the changes are reported to be confined to the surface layer of the substrates (2,4).…”

“…The reflected beam usually interacts strongly with a surface layer of the substrate which can vary from 0.1 to 4.0 p (5). Attenuated total reflection spectroscopy has been employed to show qualitatively that surface changes have occurred during glow discharge treatment of polymers (2,6). The quantitative use of a.t.r., however, has been limited by difficulties involved in the comparison of spectra recorded under various reflection conditions.…”