In water-based systems a co-solvent can also be present to improve resin compatibility.įinally, emulsions of thermoset acrylic resins are also available. In this case they are commonly identified as water-thinnable. These acrylic resins can be provided in solvent phase but if the number of carboxyl group on the polymers is high enough, they can be soluble in water. Moreover other curing agents like epoxies, which can react with the carboxyl groups, could also be used in this case. In addition to hydroxyl functions, carboxyl groups are also normally present on the polymer chains of cross-linking resins (or as free acrylic acids): they can act as catalysts for the curing reaction and improve coating adhesion. ![]() Isocyanate curing agents can be “blocked”, or made unreactive at room temperature, and curing of the resin will occur only at higher temperature in an oven (stoving coatings). The 2K are used in particular when heating in an oven is not possible. This kind of formulation (resin + curing agent) can be provided where they are already mixed together as: In the first case the R group is commonly a hydroxyl-functionalized chain allowing the reaction with melamine or isocyanate curing agents. a chemical that will react with the polymers, and Externally-cross-linked resins, which require a curing agent, i.e.We can distinguish between two types of crosslinking systems: A catalyst may also be added to promote and accelerate the chemical reaction. This can occur in specific conditions, as for instance at a certain temperature or under UV light. ![]() When reactive groups are present, acrylic resins can be cross-linked by allowing the interaction between two different polymer chains. However Styrene-Acrylic resins are often subject to yellowing and chalking, severe issues that reduce their potential applications. They are known to increase water resistance and to lead to bothĪlkali resistance and improved hardness. Styrene monomers are significantly less expensive than the acrylic ones. Styrene is probably the most used and the resulting resins are known as Styrene-Acrylic. In order to obtain a resin with specific properties, or to reduce its cost different monomers can be incorporated into the acrylic polymer. A large number of carboxyl groups will also help to solubilize the resin in water. H functionalizations, and thus the presence of carboxyl groups, can improve the adhesion on a substrate.
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