Bayhydur Xp2655 Alternative HDI Hardener

Bayhydur XP2655 alternative HDI hardener

Characterization Hydrophilic aliphatic polyisocyanate based on hexamethylene diisocyanate (HDI).

Hardener for waterborne two-component polyurethane systems.

Form supplied 100 %

Property Value Unit of measurement Method

Viscosity at 23 °C 3,500 ± 1,000 mPa·s M014-ISO 3219/A.3

NCO content 20.3 - 21.3 % M105-ISO 11909

Hazen color value < 60 M017-EN 1557

Monomeric HDI ≤ 0.24 % M106-ISO 10283

Solubility / thinnability The product is generally compatible with organic solvents such as esters or ethers. However, solubility and compatibility should be tested in each case.

Regarding the influence of the solvent (cosolvent) on the emulsibility of the polyisocyanate, please refer to the information in the section

"Properties/applications". Only PU grade solvents should be used (< 0.05 % water).

Bayhydur® XP 2655 is a crosslinking agent for waterborne systems from which reliable incorporation and high chemical resistances are required. Despite its relatively low hydrophilia, this hardener can be easily dispersed in the aqueous phase, even at low shear forces such as are typically found in trade applications. Coatings formulated with the product yield films with high gloss and very low haze. The increase in viscosity during mixing that is typical for hydrophilized hardeners, in particular with ionically hydrophilized polyol dispersions, can be controlled by prethinning with water or slight amounts of organic cosolvent.

The dispersibility of the product in water is influenced by organic cosolvents, but in different ways. The use of highly hydrophobic or highly hydrophilic cosolvents such as butyl acetate, xylene, butyl glycol acetate, dimethyl formamide or N-methylpyrrolidone generally leads to a coarser dispersion, which may cause turbidity in the coating film depending on the entire system.

On the other hand, the use of, for example, methyl ethyl ketone, methoxypropyl acetate, dipropylene glycol dimethyl ether, propylene glycol diacetate or dicarboxylic acid diester mixtures leads to fine-particle dispersions.

Because of the balance between moderate hydrophilization and high functionality, waterborne two-component polyurethane coatings formulated with Bayhydur® XP 2655 exhibit fast drying, rapid hardening with high ultimate hardness and excellent chemical resistance of the resultant films.

Bayhydur® XP 2655 can also be used as the crosslinking partner for waterborne polyol binders (Bayhydrol®) and as a crosslinker for largely pH-neutral waterborne polymer dispersions such as polyurethane, polyvinyl acetate, polyacrylate and synthetic rubber dispersions.

After addition of Bayhydur® XP 2655, the ready-to-use two-component formulation must be used within the pot life. This is not only governed by the polymer content but also by its other constituents (resin, thickener, plasticizer, etc.). With many dispersions, the end of this pot life – usually several hours – is not marked by gelling.

- Storage in original sealed Covestro container.

- Recommended storage temperature: 0 - 30 °C.

- Protect from moisture, heat and foreign material.

 

General information: Hydrophilic isocyanates are very moisture-sensitive and react with water to form carbon dioxide and insoluble ureas. The containers must always be kept tightly closed. The access of water in all forms (moist air, solvents, moist containers) must be prevented, because the generation of carbon dioxide can lead to dangerous increases in pressure. Storage at higher temperatures will result in increase of color and viscosity

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