Figure 1. UVA and NOR HALS with acrylate clear resin for high solids
coating after 2,000 hours QUV-313nm exposure. Results show UVA
mixed NOR HALS was able to minimize discoloration to the coatings.
Figure 2. UVA-H and HALS-H with polyester resin for powder coating
after 2,000 hours QUV-313nm exposure. Results show UVA-H mixed
with HALS-H was able to minimize discoloration to the coatings.
In choosing light stabilizers for high solids coatings, it is
necessary to consider the pKb of the coatings; therefore, NOR
HALS become very important in some cases as to work with a
low basicity system. Also, solubility is another key element for
coatings. A liquid type light stabilizer is a better choice, which
has no dispersion problem and is easy to use. Before and after
exposure of delta Y measurements (as shown in Figure 1) of
adding UVA and NOR HALS, coatings would receive different
degrees of protection according to its use level. Evidently, UVA
mixed NOR HALS was proven to provide a better protection
as seen in this test.
2. Powder Coatings
Powder coatings are applied by high pressure and static electrostatic spray. The resin and additives are formed and attached to the surface of the object and then cured by high
temperature heat to form a durable coating. This process results in a solvent-free coating.
Particle size is crucial in powder coatings. It is very diffi-
cult for light stabilizers to reach good homogenous dispersion
in a short time due to the small dosage. UVA-H and HALS-H,
both are novel micron grades, and developed for effectively
overcoming the obstacle of dispersion. Before and after expo-
sure of delta Y measurements (as shown in Figure 2) and
adding UVA-H and HALS-H, coatings would receive different
degrees of the protection according to each consumption level.
Evidently, UVA-H mixed with HALS-H was proven to provide
a better protection.
3. Waterborne Coatings
Waterborne coatings are an eco-friendly coating system based
on water-soluble or water dispersed resins. They are non-toxic,
odorless and nonflammable.
Liquid light stabilizers in many cases are known to not easily disperse in water-based coatings. Adding UV stabilizers directly to water-based paint systems will cause condensation
in coatings and make it difficult to spray without filtration.
Everlight offers a series of new high-performance liquid light
stabilizers that works with waterborne coatings. They can be
used directly and homogenously disperse in waterborne coat-
84 | Coatings World
www.coatingsworld.com
April 2012
