One-component polyurethan adhesive

The water adsorbed on the adherends and present in the ambient air, which is available as a reactant for the moisture-curing one-component polyurethane adhesives (Section 4.2.2). This reaction is also typical for sealing compounds on polyurethane basis (Section 4.9) used, for example, in construction engineering for the sealing of joints between window and door frames and brickwork. 

Figure 4.2 Moisture curing of one-component polyurethane adhesives.

Since these one-component polyurethane adhesives cure through reaction with water, one talks of moisture curing one-component polyurethane adhesives. Their characteristic feature is their excellent adhesiveness. Apart from adhesive applications, these formulations are applied to a great extent as sealing compounds, for example, as fitting foam glue or PU-foam (Section 4.9). 

Adhesive foams applied out of spray cans are available on the same basis as the one-component polyurethane adhesive. Due to the contact with humidity in the air or moisture of the adherends, an inherently stable, well-adhering foam develops that shows excellent sealing properties. 

At this point, an important difference compared to moisture curing, one-component polyurethane adhesives described in Section 4.2.2 has to be mentioned. While for cyanoacrylates already small traces of moisture are sufficient for a quick polymerization, polyurethanes require a considerably higher moislure amount for complete curing, because in such bonds, water in chemically bound form becomes a component of the adhesive layer. In the case of cyanoacrylates, water is merely the starter of the curing reaction. 

For repair, the concrete of reservoirs is impregnated with Silor composition to seal the concrete, strengthen it, and increase its chemical stability. Polyester cloth is glued at wall/floor joints using the one-component polyurethane adhesive UTK-M. 

This paper aims at explaining the reaction between the HMR coupling agent and one-component polyurethane adhesives used for wood lamination. 

Table 5.8 Average Tensile Properties of Cured One-component Polyurethane Adhesive According to ASTM D638-03...

One-component polyurethane adhesives for direct glazing are widely used in the automotive industry. Since about 5% of car s windshields every year are damaged. 

One-component polyurethane adhesive Adhesive containing isocyanates ernes on exposure to moisture or to heat, when latent hardener is included Primer Special coating designed to improve adhesion between adhesive and substrate - applied before adhesive application Reactive adhesives Adhesives that cure or set when exposed to heat, moisture, radiation, etc. 

In the early 1980s, Sika diversified into the chemistry of elastic adhesive bonding for industrial applications. With eight production centres in three continents, Sika is now the world s largest manufacturer of one-component polyurethane adhesives and sealants. The customer oriented solutions and services of the Sika Industry Division are marketed to the following market sectors, where they are the leaders in their field ... 

One-component polyurethane adhesives have also become popular in recent years. These adhesives have a single component and depend on moisture for curing. The moisture is sometimes available in the wood or the atmosphere, but it is common practice to dampen the surface before applying the adhesive. One has to be careful to use the right amount of adhesive and to clamp the parts, because the adhesive generates foam on curing and tends to expand. 

Excessive shear strain should generally be avoided in adhesive joints because cohesive failure is likely to occur once shear deformation leads to a buildup of tensile stress at the end of the overlap bond area. In practice, it has been found that strain in assemblies with rubbery moisture curing one-component polyurethane adhesives should be limited to values of shear strain tany below 0.5. Specific viscoelastic pressure sensitive tapes may even tolerate shear strains of tany up to 2. The maximum tolerable strain of structural adhesive joints using adhesives with a highly cross-linking density, however, is typically more than one order of magnitude lower than that. 

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