Adhesion of the coating

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

When the photostabilization of a polymer material is to be obtained through such a surface treatment process, it is all important to make sure that the protective effect will last throughout the service life and therefore to ensure a long-term adhesion of the coating onto the substrate. This can be best achieved by promoting a grafting reaction between the two elements (20). For that purpose, the photoinitiator was partly incorporated in the top layer of the PVC plate by a surface treatment with an acetone solution. Upon UV-irradiation of the resin-coated sample, the following reactions are expected to occur ... 

Cross-cut ( -cuf) According to ASTM D 3359, method B (ISO 2409), a lattice with 6 cuts in each direction is made in the film to the substrate. Then, pressure tape (TESAPACK 4287) is applied over the lattice and then removed, and adhesion is evaluated by comparison with descriptions and pictures. The method is used to establish whether the adhesion of the coating to the substrate may occur between the coats (adhesive break) or in the coating (cohesive break). 

However, several drawbacks still limit the quality of the interface and the implant biointegration the poor adhesion of the coating on the titanium surface and its scaling either during implantation or in the long run, and the decomposition of... 

T50I(NPG)/PMDA was of particular interest because of its adhesive characteristics, oxidative stability, and polymer cost. Table III shows the improvement in adhesion obtained when various substrates were coated with blends containing this polyester (acid number 39). As indicated in the table, the ease of obtaining adhesion on the different substrates decreased approximately in the following order brass > steel > copper > chrome-coated steel > aluminum > nylon 66 > poly (ethylene terephthalate). In spite of the wide differences in structure and polarity of the various polymers, the carboxylated polyester significantly improved the adhesion of the coatings. 

Four coats of the above were applied, with the second coat consisting of the lead carbonate portion. Figure 9 indicates that a 3/64 inch film will give 1000 F. insulation. The adhesion of the coating was good, but the silicate of soda caused poor flexibility and water resistance. 

After exposure to such a sequence, the specimens should be tested for adhesion of the metal coating by means of the cross-hatch test described in Adhesion above. In a comparison with the unexposed control samples, there should be no deterioration in the adhesion of the coating, reflectivity, or the condition of the surface. 

The adhesion of a coating to plastic is related to the substrate wettability and also to physical-chemical forces. Both covalent (bond formation) and dispersive (London or van der Waals) forces are responsible for the adhesion of the coating due to physical-chemical forces. 

A typical washcoat on a metallic structure is shown in Figure 25. The significantly stronger adhesion of the washcoat on the anodized metal can be illustrated by testing the adhesion of the coating layer by using an ultrasonic treatment. Whereas the untreated metal loses approximately... 

Figure 24.14 Schematic representation of water diffusion through a coating with and without water-insensitive adhesion of the coating to the substrate.

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