Advantages and disadvantages of double curing in UV coatings

Dual curing is a new technology, which combines the advantages of typical thermal curing and UV curing systems. It can provide excellent scratch resistance and chemical resistance of UV coatings, while allowing shadow curing through thermal reaction. This feature makes dual curing an attractive choice for automotive interior applications. The flexibility of its process also allows the applicator to adjust and modify the existing production line without building from scratch.

As the surface meaning of the word “double curing” expresses, this technology is the combination of UV curing and heat curing resins. UV acrylate monomer and oligomer, photoinitiator, acrylic resin and solvent constitute the basic composition. Other modified resins and additives can also be included in the formula. The combination of these raw materials forms a system that has good adhesion to many substrates, while providing impeccable surface hardness, scratch resistance and wear resistance.

The screening matrix of dual curing coatings is generally divided into four categories: adhesion, scratch resistance, chemical resistance and weather resistance. The heat-curing coating can have the “self-healing” characteristic, and the surface abrasion and scratch will eventually disappear due to the flexibility of the resin. Although this is a favorable feature from the scratch point of view, it also makes the coating vulnerable to various chemical agents. UV coating usually has a high degree of cross linking surface, showing excellent scratch resistance rigidity, but the coating is fragile and easy to produce adhesion and weathering problems.

There are only two processing requirements for double curing coating: oven for thermal curing and ultraviolet lamp for acrylate curing. This enables the coater to transform the existing paint production line without building a new paint production line.

One of the biggest obstacles of dual curing technology is the limitation of color mixing. Most UV curing systems are transparent or light-colored, because color will interfere with UV curing. Pigments, pearl powder and metal flakes can inhibit curing by scattering ultraviolet radiation and preventing enough ultraviolet rays from penetrating into the coating (Figure 3). The result is the formation of uncured acrylate near the substrate interface. The higher the coating accumulation of these colored coatings, the worse the curing.


Post time: Mar-15-2023