Surface-located radical reactions

Another advantage of the activator is the ability to cure a film or drop of the adhesive on a surface. The activator can be applied either to the surface being coated or to the top surface of the adhesive. The adhesive cures to a clear, hard, dry plastic that can be used to locate parts in position or to form a protective coating. Because the curing reaction is ionic, it is not sensitive to oxygen as are free-radical reactions, and it will cure through to the surface without the tackiness associated with free-radical curing systems. 

Recently, Stair and coworkers [10, 11] developed a method to produce gas-phase methyl radicals, and used this to study reactions of methyl groups on Pt surfaces [12] and on molybdenum oxide thin films [13]. In this approach, methyl radicals are produced by pyrolysis of azomethane in a tubular reactor locat inside an ulttahigh vacuum chamber. This method avoids the complications of co-adsorbcd halide atoms, it allows higher covraages to be reached, and it allows tiie study of reactions on oxide and other surfaces that do not dissociate methyl halides effectively. 

The horizons lie approximately parallel to the soil surface and are the product of weathering processes. The physical and chemical differences among the horizons alter reactions between the soil and contaminant, and the soil and microorganism. As a result, the efficiency of bioremediation at one location in the soil profile may differ radically from that at another point in the same profile. 

---