UV-curing & weatherproof in corrosive environments
There is great growth potential for UV-curing binders in high-performance outdoor coatings. Isocyanurate-based materials, currently the first choice for many UV-curing outdoor applications, are hard, weatherproof and scratch-resistant but since they have a very high viscosity, they need diluting with solvents or monomers (reactive thinners).
Allophanate-modified urethane acrylates, a novel class of UV-curing resins, are low viscous alternatives to established outdoor-resistant urethane acrylates based on isocyanurates. Since they have a more flexible backbone, they exhibit a much lower viscosity but perform just as well in terms of outdoor stability, scratch resistance, hardness and chemical resistance. There are options to modify the basic allophanate resin: multifunctional acrylates in the synthesis improve crosslink density and chemical resistance; and the incorporation of an elastifying double bond carrier is a suitable solution if more elasticity is needed.
Testing the corrosion and scratch resistance of UV-cured coatings
Allophanate urethane acrylates are ideal for UV-curing coatings on plastic and metal substrates. The low viscosity of these allophanate urethane acrylates even permits formulations without any reactive thinner or solvent. All allophanate urethane acrylates have already proved their excellent stability in different accelerated weathering tests. Thanks to their ability to counterbalance the hydrophilic effect of common adhesion promoters for metal, allophanate urethane acrylate-based coatings can withstand even a corrosive environment.
Such allophanate urethane acrylates can thus be optimally formulated to meet the specific coating needs of different substrates. As Dr. Wolfgang Fischer from Bayer MaterialScience explains, “allophanate-based UV resins give our customers the greatest possible flexibility in the formulation of their coatings thanks to their wide versatility and the absence of reactive thinners.”
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