Plasma surface preparation

Epoxy and nitrile-phenolic adhesives have been used to bond polyolefin plastics after plasma surface preparation. Shear strengths in excess of 3000 psi have been reported on... 

Surface engineering means both surface preparation and sterilization of the modified surface. A recent review of surface engineering [2] indicates that plasma surface preparation is well adapted to the preparation of biomaterials because it is easy to reproduce and clean the treated sample, and good for the environment (no pollution) as weU. This type of treatment can also be appHed in a clean room. Several plasma processes are possible for surface engineering. 

An important newer use of fluorine is in the preparation of a polymer surface for adhesives (qv) or coatings (qv). In this apphcation the surfaces of a variety of polymers, eg, EPDM mbber, polyethylene—vinyl acetate foams, and mbber tine scrap, that are difficult or impossible to prepare by other methods are easily and quickly treated. Fluorine surface preparation, unlike wet-chemical surface treatment, does not generate large amounts of hazardous wastes and has been demonstrated to be much more effective than plasma or corona surface treatments. Figure 5 details the commercially available equipment for surface treating plastic components. Equipment to continuously treat fabrics, films, sheet foams, and other web materials is also available. 

Surface preparation of the dental implant prior to implantation wiH have an effect on corrosion behavior, initial metal ion release, and interface tissue response (316). The titanium and titanium aHoy dental implants in present use have many forms to assist bone ingrowth attachment including cylinders with holes, screw threaded surfaces, porous surfaces, and other types of roughened surfaces. Methods used to produce porous surfaces iaclude arc plasma... 

In Section 4.3 several recently developed and experimental surface preparation methods for steel such as conversion coatings, plasma spray and sol-gel that attempt to simultaneously improve durability and bond strength over grit blasting will be discussed. 

Despite the progress outlined in this chapter, much work remains to be done in the metal surface preparation arena. For example, there is still no ideal surface preparation method that does for steel what anodization processes do for aluminum and titanium. The plasma spray process looks encouraging but because it is slow for large areas and requires rather expensive robot controlled plasma spray equipment, its use will probably be limited to some rather special applications. For more general use, the sol-gel process has potential if future studies confirm recently reported results. 

Several environment-friendly surface preparation for the treatment of mbber soles with radiations have been recently studied. These treatments are clean (no chemicals or reactions by-products are produced) and fast, and furthermore online bonding at shoe factory can be produced, so the future trend in surface modification of substrates in shoe industry will be likely directed to the industrial application of those treatments. Corona discharge, low-pressure RF gas plasma, and ultraviolet (UV) treatments have been successfully used at laboratory scale to improve the adhesion of several sole materials in shoe industry. Recently, surface modification of SBR and TR by UV radiation has been industrially demonstrated in shoe industry... 

Fig. 7 Atomic force microscopy image illustrating defect structures in wrinkled surfaces prepared by plasma treatment of stretched PDMS and subsequent relaxation...

Yoon TH, McGrath JE (1991) Effect of surface preparation and thermoplastic ahesive structure on the adhesion behavior of peek-graphite composites. Mater Res Soc Symp Proc 190 (Plasma Process Synth Mater) 3 137-142... 

To obtain a usable adhesive bond with polyolefins, the surface must be treated. A number of surface preparation methods, including flame, chemical, plasma, and primer treatments, are in use. Figure 16.4 illustrates the epoxy adhesive strength improvements that can be made by using various prebond surface treatments to change the critical surface tension of polyethylene. 

In the case of a photoresist, the ultimate definable feature size together with the ability of the material to withstand either chemical etchants or plasma environments determines the domain of utility. The feature size is in turn determined by the wavelength required for exposure, the sensitivity and contrast of the resist, and the dimensional stability of the material during exposure, development, and subsequent processing. Adhesion of the resist to the substrate is critical both for patterning and use, and adhesion can be affected by surface preparations, and by residual stresses developed during deposition and cure. While photo-imagable polyimides have been introduced, their principal intended application is as a component of the finished part, either as passivant or interlevel dielectric (see below). 

A nonchromated, water-borne primer applied to [2B] alloy samples, with the appropriate surface preparation and plasma deposition of an ultrathin plasma polymer, was also compared to controls prepared by depositing a chromated primer on chromate conversion-coated A1 substrate. The same comparison was also performed for IVD Al-coated 2024-T6 substrates (pure aluminum is deposited by ion vapor deposition process on aluminum alloy 2024-T6). In the latter case, the primer could not be removed from the IVD Al-coated panels that were treated with the plasma polymer prior to spray primer application. It is interpreted that the water-borne spray paint penetrates into the column structure of the top surface of the IVD Al-coated substrates when the surface energy was modified by the application of a plasma polymer. This effect could be viewed as interactive coating with a porous surface. 

Table 31.1 Adhesion Test Results of Chromated Spray Primers [Deft 44-GN-36 (A) and Courtauld 519X303 (G)] to A1 Alloys Prepared with Chemical Cleanings and Plasma Surface Treatments...

From the XPS analysis results, it was found that TMS plasma coatings prepared in a closed system have a carbon-rich surface, which is similar to TMS polymers followed by methane plasma deposition, i.e., T/C as described in a flow system. The adhesion study also showed that the T/C plasma treatment on aluminum alloy provided excellent adhesion to spray paint primers. The primer adhesion performance of closed system TMS plasma polymers was also examined. Since the porous surface... 

Most commercially available cathodic E-coat paints contain lead in the recipe, and the removal of lead from E-coat generally leads to an appreciably inferior performance on scab test [7]. The effect of lead-free E-coat on the corrosion performance of plasma interface-engineered systems was examined and the results are shown in Table 33.3. The elimination of lead resulted in significant deterioration of the corrosion protection of the phosphated samples. In a strong contrast to the conventional surface preparation, the plasma interface-engineered systems showed... 

None of the smooth surfaces prepared by the depositing of plasma polymer on the smooth surface of Silastic tubing showed detectable thrombus formation by gamma camera imaging. Therefore, they were evaluated by measurement of relative rates of platelet consumption. Table 35.7 shows the results obtained using the plasma polymers described previously [5]. 

The application of the tools, techniques, methods, and expertise of AMO physics to the many unanswered questions posed by the processes at the interface of the plasma with the surrounding walls or at the surface in etching and deposition applications (plasma-surface/wall interactions) will provide a fertile ground for opportunities and challenges in applied AMO physics. The coupling between gas-phase (volume) processes and the surface/wall processes (see Fig. 1) and the need to study surface/wall processes with realistic, dirty surfaces (rather than with the clean, ultrahigh-vacuum-prepared, well-characterized surfaces that are used in conventional surface science experiments) provide numerous opportunities and challenges for future experimental and theoretical AMO physics research. 

M. Strobel, C. S. Lyons, K. L. Mittal, Eds. Plasma Surface Modification of Sample Preparation. Polymers Relevance to Adhesion VSP Utrecht, The Netherlands,... 

---