Film-formation promoters

Film-formation promoters, which are closely related to flow agents, reduce the film-forming temperature for film formation from dispersions, leading to a surface that is as pore-free and uniform as possible. Certain high-boiling glycol ethers and glycol ether esters are used, often in combination with hydrocarbons. 

Water-dispersible resins contain carboxyhc groups which are neutralized using base or amine compounds. This solubilizes the resin in solution and also promotes pigment wetting. Film formation occurs by the evaporation of volatiles foUowed by cross-linking through ambient cure oxidative reactions or elevated temperature reactions. Solvents, most commonly glycol ethers, are used to promote film formation and improve film quahty. 

The oxidation products are almost insoluble and lead to the formation of protective films. They promote aeration cells if these products do not cover the metal surface uniformly. Ions of soluble salts play an important role in these cells. In the schematic diagram in Fig. 4-1 it is assumed that from the start the two corrosion partial reactions are taking place at two entirely separate locations. This process must quickly come to a complete standstill if soluble salts are absent, because otherwise the ions produced according to Eqs. (2-21) and (2-17) would form a local space charge. Corrosion in salt-free water is only possible if the two partial reactions are not spatially separated, but occur at the same place with equivalent current densities. The reaction products then react according to Eq. (4-2) and in the subsequent reactions (4-3a) and (4-3b) to form protective films. Similar behavior occurs in salt-free sandy soils. 

In addition, with high solid content of the cooling water and at high flow velocities, severe corrosive conditions exist which continuously destroy surface films. Cathodic protection alone is not sufficient. Additional measures must be undertaken to promote the formation of a surface film. This is possible with iron anodes because the anodically produced hydrated iron oxide promotes surface film formation on copper. 

Synergistic phenomena similar to those described for etching are expected during film formation processes. In particular, the creation of adsorption and nucleation sites, along with the promotion of chemical reactions and the dissociation of adsorbed species because of particle bombardment,... 

The properties of silicon dioxide films also depend upon all plasma deposition parameters. Temperature is the critical parameter (240), although the compressive stress level varies with rf frequency (237, 240). Film topography can be varied during deposition by altering ion bombardment conditions (242, 243). In particular, the incorporation of Ar in the deposition atmosphere enhances sputtering and thus promotes conformal step coverage during film formation (243). 

Povidone K 90 is only seldom used for film coating (see Table 87). Its most important properties here are film formation, adhesion promotion [276], pigment dispersion and the improvement of the solubility of other film-forming agents and of the final coating in water [100]. 

The ultra-thin organie film formation on TiOj templates was effectively promoted through the speeifi-eally designed, bifunctional self-assembly molecules (SAM) 5-eyano-2-(butyl(4-phosphonie acid))-3-butyl-thiophene (CNBTPA), whereas DBQT and DBST did not improve their layer structure when they were evaporated on the SAM layer (images not shown). 

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