Лако-красочные материалы — производство

Boerio and co-workers [32,39] showed that the average shear stress of epoxide/titanium lapshear joints primed with g-APS at either pH 10.4 or 8.0 showed almost no decrease in strength after water immersion at 60°C for 60 days; unprimed controls lost 75% of their original strength. Epoxide/iron joints primed with APS at pH 8.0 retained 75% […]

Bascom [35] employed a variety of techniques in his study of the structure of silane films deposited on glass and metal substrates and concluded that vinyl-, amino-, and chloro — functional silane films were deposited as polysiloxanes, some of which could easily be removed from the surface by organic solvents or water. Contact-angle measurements on […]

The reactions of interest in silane coupling are summarized below. (a) Hydrolysis of the silane group: pH or catalyst R“SiX, + 3H20—————————————— ► R-Si(OHb +3HX ( 1 where HX is usually an alcohol. Table 2 Typical Silane Adhesion Promoters Commercially Available Chemical Description Structure Functional Group With With Polymer Substrate 3-Chloropropyltrimethyl ClCH2CH2CH2Si(OCH3)3 Chloro Methoxy oxysilane […]

Silanes of the general structure RSi(OR)3, where R is an organofunctional group and R0 a hydrolyzable group, constitute the most technologically important group of adhesion promoters in use today and have a solid background of associated theory. Silane mole­cules are bifunctional, containing polar silanol groups and organofunctional groups cap­able of reaction with polymers. The range […]

In general, adhesion promoters may be used as pretreatments or as additives. In the former case the promoter is used either as a solution in a suitable solvent or solvent mixture or as a formulated primer [26]; in the latter case they may be incorporated into the adhesive in a self-bonding concept [25]. The technique […]

In addition to the stated theories of adhesion promotion, there are other mechanisms that may be both operative and important and are of general application. 1. Interpolymer Networks/Chain Tangling It has been suggested that in the case of silane coupling agents, interdiffusion of siloxanol segments with polymer molecules may be a factor in bonding thermoplastic […]

This theory postulates that a primary mechanism by which silane coupling agents improve initial and wet adhesion is by reaction with the oxide surface on a metal to increase the cohesive strength of the oxide [23] and certainly, in the case of aluminum oxide, increase the wet strength of the oxide by inhibiting hydration of […]

Best regarded as a combination theory, it postulates the chemical reactions between cou­pling agent, substrate, and polymer of the chemical bond theory together with the rigid interface of the restrained layer theory and the plastic interface of the deformable layer theory. It allows for stress relaxation by the reversible breaking of stressed bonds without loss […]

Erickson and Plueddemann suggest that particularly in filled systems, complete wetting of the mineral surface will improve adhesion by physical adsorption that would exceed the cohesive strength of the polymer. However, it is difficult to see how physical adsorption provides bond reinforcement when the polymer is in competition with water and possibly other weakly bonded […]

This theory postulates that the interface zone is plastic, allowing stresses between the polymer and mineral surfaces to self-relieve without bond rupture. Internal stresses are thus reduced. It has been suggested that in the case of a silane, the film is too thin to allow this [11]. However, it is possible that the presence of […]