Reactive adhesion promoters types

The (physically wetting) polyaniline primer CORRPASSIV was compared with a fast-drying two-component epoxy resin primer (Messrs. Finalin, Type 144) and a metal-reactive two-component primer with adhesion-promoting properties (Type 918). All three primers were coated with a two-component polyurethane paint (B412). CORRPASSIV, both with and without top coat, exhibited no rust formation beneath the primer. The slight undermining receded after the test, and even within the cross and scratch injuries, it was virtually impossible to detect any corrosion. 

By means of OH- and COOH-containing plasma polymer layers the quahfica-tion of these layers as models of single-type functionalized adhesion promoters with variable concentrations of functional groups should be proved. The plasma-initiated copolymerization of acrylic acid with ethylene or 1,3-butadiene is shown in terms of measured COOH concentration as a function of the composition of the comonomer mixture in Fig. 18.3. Depending on the co-monomer reactivity, a more linear correlation (butadiene), or a parabolic behavior (ethylene), between precursor composition and COOH groups produced was observed. For each type and concentration of functional group, its concentration was determined by chemical derivatization followed by XPS analysis as described in Section 18.2.5. 

Phenolic resins are of two types, reactive and nonreactive. Nonreactive resins tend to be oligomers of alkyl-phenyl formaldehyde, where the para-alkyl group ranges from to C4 to C9. Such resins tend to be used as tackifying resins. Reactive resins contain free methylol groups. In the presence of methylene donors such as hexamethylenetetramine, crosslink networks will be created, enabling the reactive resin to serve as areinforcing resin and adhesion promoter. 

The soap contains cationic surfactant as well as hydrochloric, or less usually, acetic or phosphoric acids. The acids are needed to convert amine-type emulsifiers to their protonated cationic forms but also to inhibit the ionization of acid groups in the bitumen. Cationic soaps typically contain 0.5-2.0% cationic surfactant, acid to pH 1 to 5, and optional additives such as water-soluble thickeners, electrolytes, latex, stabilizers and adhesion promoters which modify the physical properties or reactivity of the emulsion, or the properties of the bitumen film when cured. Some typical emulsion recipes are shown in Table 14.10. 

Today a broad variety of binders is available world wide. For each application alternative systems are possible. Nevertheless there are still local differences in availability and prices for different dispersion types. Of course not only the main monomer is influencing the properties, sometimes minor monomers, e.g. reactive monomers like adhesion promoters are more important also for the compatibility with the applied preservatives. 

Primers can also chemically react with the adhesive and adherend to provide greater joint strengths. This type of primer is referred to as an adhesion promoter. The use of reactive silane to improve the adhesion of resin to glass fibers in polymeric laminates is well known in the plastic industry. 

In addition, these or similar types of monomers may have utility as adhesion promoting agents for dentin since collagen has a certain natural reactivity towards aldehydes (e.g., maturation of collagenous tissue, tanning of leather). 

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