Surface metal/polymer interfaces

Friction coefficient at the polymer/metallic equipment surface interfaces. 

The chapters in this volume present a concise overview of surface analytical techniques from the specific viewpoint of surface morphology and its modification at the polymer-metal interface. A consistent picture begins to emerge of the chemical reactions occurring on metal deposition and why this leads to metal adhesion. The coeditors hope this information will be timely and useful. 

In this paper some applications of static SIMS to a variety of modified polymer surfaces are described. They include plasma treatments in reactive and inert gases, corona treatment in air, as well as thermal and ion beam modifications of polymer-metal interfaces. The examples presented and discussed here primarily serve to illustrate the capabilities of static SIMS for the study of such surfaces and interfaces. More detailed discussions of the actual chemical processes that proceed in several of the systems cited will be published elsewhere. 

The metal polymer interface can be studied in a variety of ways using surface science methods. Recently, much emphasis has been placed on the understanding of the initial stages of metallization of polymers. In particular, the role of metal-organic interactions as they relate to the fundamentals of adhesion mechanisms are of interest. One experimental approach is to examine the first monolayers of metal as they are deposited on a polymer surface (1), i.e the polymer is the substrate. However, the organic polymer-metal interface may be studied in the opposite perspective, via understanding the roles of organic molecular or macromolecular structure and chemistry of the metal surface qua substrate (2). In the present paper, recent ion and electron spectroscopic studies of the... 

New experimental results on specific polymer material problems are presented in the last nine chapters. Several cases involve the study of polymers from commercial sources. The topics include (1) surface chemistry as induced by (a) outdoor weathering, (b) chemical reactions, and (c) plasma exposure (2) chemical bond formation at the polymer -metal interface and (3)biomaterials characterization and relationship to blood compatibility. 

Polyimide was used as a model material in studies of polymer metal interfaces where metal layers were formed by metallization, plasma deposition, chemical vapor deposition, electrochemical deposition, etc In most of the cases studied, the interpenetration of metal was so good that the metal layer could not be removed by any other means but abrasion. An investigation of interface, determined that the metal particles were found in the surface layers in diminishing quantities perpendicular to the surface and not, as expected, in the form of a sharp borderline between the metal and polymer. Some difficulties exist when metallized polyimides are used for chip production. These diffuse layers of metals complicate design and performance due to the gradients of conductivity which they produce. 

The rate of metal reduction is dependent on the intrinsic redox states of the polymer, the effective surface area, and the pH of the solution. The XPS NIs core-level spectra of protonated and de-protonated PAN and PPY after metal reduction reveal that the intrinsic stnjcture of each polymer at the polymer/metal interface remains intact, even at [metal]/[N] ratios substantially above I [81,112]. Figures 3.33 (a)-(c) show, respectively, the NIs, Au4f and C12p core-level spectra of a DP-PPY film recovered after 48 h from a dilute chloroauric solution. The corresponding core-level spectra after the film has been treated with 0.5M... 

For polymer-polymer sliding pairs,(ll) adhesion appears to be the dominant mechanism of polymer friction. Adhesion can also take place at the polymer-metal interface provided that surface roughness is below a certain value.(12) For a smooth surface, it is difficult to differentiate fatigue from adhesive wear.(5)... 

The detailed study of molecular mechanisms involved in adhesion requires an atomistic treatment of the substrate surfaces and their interaction with the organic components contained in the adhesive. Interesting aspects of the substrate-adhesive interaction include the preferential molecular orientation due to the interaction at the surface [1] or the influence of the initial stages of polymer grafting on the stability of polymer/metal interfaces [2]. The structure and composition of the interface can have a decisive effect on the properties of the re-... 

There exist other explanations for the generation of TSC in M1-P-M2 systems. For instance, the authors of [58] attempted to prove that voltage in the open circuit of the system with a layer of polyvinyl alcohol depended on the difference of work functions of the electrodes. This explanation can hardly be accepted at least because there is always an oxide film on the metal surface that experiences interfacial transformations at the polymer-metal interface. It is evident (Table 4.5) that the work function difference can be correlated neither with the current value in the M1-P-M2 systems nor with its direction. 

While the adsorption theory is the most accepted one, mechanical interlocking comes into play in case of substrates with a special kind of roughness such as galvannealed steel where the liquid can spread into cavities and thereby interlock with the substrate. The diffusion theory does not play an important role for polymer-metal interfaces. The contribution of the electrostatic theory is not easy to estimate. However, the electrical component of the adhesive force between the planar surfaces of solids becomes important if the charge exchange density corresponds to 10 electronic charges, meaning about 1% of the surface atoms [71]. 

The polymer-metal interface between the ionic EAP and the embedded elec-trode(s) was significantly improved using plasma treatment. Based on the water drop surface contact angle tests and mechanical testing, oxygen plasma-treated stainless steel and titanium led to much better adhesion between the electrodes and the EAPs. For both stainless steel and titanium, XPS confirmed the presence of a... 

Stud or butt tests representing pull-off tests used for the measiuements of the adhesion characteristics between an ink/paint coating and the substrate. An adhesive is applied to the paint coating, and a metallic stud made of aluminum is glued onto the surface by the adhesive applied to the paint coating. Subsequently, the pull force is utilized perpendicular to the substrate surface with a constant rate. This measurement provides an excellent measurement of adhesion for systems, for example, for polymer-metal interfaces [98]. Figure 8.14 schematically illustrates the puU-off test schematically [99]. 

Both electronic and medical applications of plasma polymers have been reported [54-61]. Most of these investigations are on the interface between polymers and inorganic materials, for instance, metal/polymer interfaces in structural adhesive joints, and cation diffusion along polymer/metal interfaces under an applied electric potential. In another reference, more specific aspects for electrical and electronic applications [59] were treated, wherein protective films for microcircuitry, and for wettability were explained. The use of such film for surface treatment has also been examined. 

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