Bonded films abrasivity

Starch pyrodextrins and British gums have the abiUty, in aqueous dispersion, to form films capable of bonding like or unlike materials. Thus, they have uses as adhesives for envelopes, postage stamps, and other products. These dextrins are used in glass-fiber siting to protect the extmded fiber from abrasion, and as binders for metal core castings, water color paints, briquettes, and many other composite materials (qv). 

Rider and Amott were able to produce notable improvements in bond durability in comparison with simple abrasion pre-treatments. In some cases, the pretreatment improved joint durability to the level observed with the phosphoric acid anodizing process. The development of aluminum platelet structure in the outer film region combined with the hydrolytic stability of adhesive bonds made to the epoxy silane appear to be critical in developing the bond durability observed. XPS was particularly useful in determining the composition of fracture surfaces after failure as a function of boiling-water treatment time. A key feature of the treatment is that the adherend surface prepared in the boiling water be treated by the silane solution directly afterwards. Given the adherend is still wet before immersion in silane solution, the potential for atmospheric contamination is avoided. Rider and Amott have previously shown that such exposure is detrimental to bond durability. 

Plasma films are usually highly cross-linked, resistant to higher temperatures, resistant to abrasion and chemical attack, and are highly adherent to the surface. Adhesion to the surface is generally high both because the growing polymer complex can fit the surface contour and thus lock-itself in (physical adhesion), and because in many instances, the species are active enough to chemically react with the surface molecules to chemically bond to the surface. The surface can be prepared so that the chemical reaction is enhanced. 

In a bonded coating as applied, the molybdenum disulphide crystallites are randomly oriented . The static coefficient of friction is therefore quite high, typically between 0.1 and 0.3, and the films can be quite abrasive. The actual degree of abrasivity depends on the hardness of the coating, the particle size of the coating, and the way in which the coated surface is loaded against a counterface. 

Slurry Abrasive The slurry abrasive provides the mechanical action of CMP. Size and concentration slurry have a different effect on mechanical abrasion. However, the abrasive can also have a chemical effect as in the case of glass polishing with ceria abrasive where the ceria forms a chemical bond with the glass surface or in the case of alumina, which seems to create surface defects on SiOj films polished in pH, in the range of 5 to 8. 

A coating prepared by the hydrolysis of an alkytri-alkoxysilane in the presence of an acidic silica sol exhibits a number of new and interesting features. It is soluble in an alcohol-water solution, can be readily applied to transparent plastic articles, and cured at temperatures below the Tg of the plastic to form a clear, hard, chemical and abrasion resistant coating. The cured film consists of small silica particles chemically bonded within a silicone resin matrix. 

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