UV Coatings
June 2014 www.coatingsworld.com Coatings World | 39
Dispersion Tests
Waterborne UV curable coatings are based on water soluble or
water dispersed resins. It is non-toxic, odorless and nonflammable. Liquid light stabilizers are normally not easy to disperse in
water-based UV curable coatings. Adding UV stabilizers directly
to water-based paint system will cause condensation in coatings
and make it difficult to use. After mixing together, we use filter
paper to test.
If the residual is less, the performance is better. On the other
hand, it can be used directly and homogenously disperse in waterborne UV Curable resin. According to dispersion test, NLS is
the best performance in both systems. Photos of 10% different
types of light stabilizers in waterborne UV curable coating is
filtrated tested (as shown in Figure 2).
Minimal Energy to Reach Curing Tests
Waterborne based UV curable coatings were made with wire-wound rod on coated Leneta charts. The dry film thickness
(DFT) was 15μm and heated in an oven at 60˚C for 2 min. The
next were cured under a 1 x 150w/cm high-pressure Hg lamp.
Cure speed was recorded when coating left no visible marks after a finger nail scratched across the coating surface a few times.
The result shows that NLS would not have negative impacts to
cur speed (as shown in Figure 2).
Weathering Test
Before and after exposure of delta Y measurements (as shown
in Figure 3) of adding NLS, coatings would receive different
degrees of the protection according to each consumption level.
Evidently, a higher use level provides a better protection.
Experiment procedure:w
Model: Q-U-V Accelerated Weathering Tester
Test Model: ASTM G154-1(QUV with UVB-340 light bulb)
Test Time: 120 hours
Material: Plastic
Characteristic
Polyurethane Dispersion ( for water-based system )
Photoinitiator ( for water-based system )
Table 2: Compositions of waterborne UV model formulation
Figure 1: Photos of 10% different types of light
stabilizers in waterborne UV curable coating is
filtrated tested
Residual = 6.5%
10% NLS
Residual=80.5%
10% A
Residual =75.4%
10% B
Figure 2: NLS is with waterborne UV-curable coatings for
plastic coating. Results show NLS would not have negative
impacts to cure speed
Figure 3: NLS is with UV-curable clear resin for
plastic coating after 120 hrs QUV-340nm expo-
sure. Results show NLS was able to minimize
discoloration to the coatings
