Waterborne UV-Curable Coatings
February 2016 www.coatingsworld.com Coatings World | 47
is a collection of mathematical and statistical techniques for empirical model
building. By careful design of experiments, the objective is to optimize a response (output variable is ΔY) which is
influenced by several independent variables [input variables are NLS (%) and
DFT]. The highlighted area from this
model is the optimal result in reducing yellowing during the curing process
(Figure 2).
Minimal Energy to Reach Curing Tests
Water-based UV--curable coatings were
prepared using a wire-wound rod on
coated Leneta charts. The dry film thickness (DFT) was 60 μm and coatings
were heated in an oven at 50 ℃ for 10
min. They were then cured under a 1 x
150 w/cm high-pressure Hg lamp. Cure
speed was recorded when the coating left
no visible marks after a finger nail was
scratched across the coating surface a
few times. The result shows that the NLS
would not have a negative impact on cure
speed (Figure 3).
Results
The results confirmed our objective
which was to show that the NLS package effectively reduces yellowing during the curing process and does not have
an impact on cure speed. Furthermore,
data also suggests that increasing film
thickness does not improve the yellowing problem.
Conclusion
Eco-Friendly coatings are the future trend
in coatings development. This article
highlighted the benefits of using a NLS in
a waterborne UV-curable coating system
and gives the formulator more options to
choose from.
Coating manufacturers may still need to
run the experiments to confirm coating systems compatibility. Also, a tailor made UV
absorber and light stabilizer package can be
offered to fulfill your special needs. CW
For more information: Tel: +886-3-
4837682; Fax: +886-3-4837683; gigi@
ecic.com.tw; www.everlight-uva.com
Table 6: The effect of reducing yellowing with NLS and DFT in a waterborne UV-curable model formulation.
Figure 1: Effect of reducing yellowing of NLS and DFT during curing.
The
ΔY = 2.75 - 1.26*(NLS%) + 0.032*DFT + 0.451*((NLS% - 2.25))2 ± 2*1.05 Equation (1)
Figure 2: The response
surface methodology of
reducing yellowing of NLS
and DFT during the curing
process test.
Figure 3: NLS in a waterborne
UV-curable coating for plastic.
