in clear UV-cure formulations is the much
lower cost compared with that of the
resin. Fillers typically cost on the order
of ten to twenty times less. This suggests
that adding 5 µm N.S. at 5% by weight
on resin solids will reduce the formulation cost by approximately 5%. Adding
10% by weight will reduce applied film
cost by 10%; 15 addition equals 15%
reduction in cost, and so forth. The cost
analysis for the UV-cure test formulations
are provided in Figure 14.
Additionally, it was shown that 5
µm N.S. has a synergistic effect with
the photoinitiator, allowing the system
to maintain cure with a lower percentage of photoinitiator in the system on
the order of 10-20%. The ability to
lower the amount of photoinitiator by
10-20% at any given loading level can
lower the formulation cost by an additional 1-2%. In thin film UV-cured
applications like OPV and inks, the
potential to load 5 µm N.S. as high
as 20-25% is realistic. Of course the
maximum allowable filler loading depends on the applied film thickness
and haze and clarity tolerances in a
given application.
Conclusion
Nepheline syenite is a versatile and
unique functional filler, possessing properties that are useful in a wide variety of
clear and opaque coating applications.
Ultrafine nepheline syenite has a refractive index and physical properties that
are particularly well-suited for enhancing
performance in radiation curable coatings, inks, and adhesives.
Using real-time FTIR analysis, the
effect of ultrafine nepheline syenite
on curing rate was evaluated. It was
found that ultrafine nepheline syenite accelerates cure rate in UV-cure
PUD coatings at any loading level
and applied film thickness, and can
potentially replace 10-20% of the photoinitiator. The DOE study confirmed
that the peroxide photoinitiator level
is the most important factor in determining cure rate, which was expected,
and that the level of 5 µm N.S. is also
an important factor.
Additionally, highly transparent and
functional fillers like ultrafine nepheline
syenite are an excellent tool for lower-
ing formulating cost, while enhancing
mechanical performance and ensuring
excellent and non-interfering UV-curing
behaviors. Future investigation will
consider the mechanism by which ul-
trafine nepheline syenite enhances the
UV curing behavior. The potential for
other natural ultrafine hard silica and
silicate fillers, with low and different
R.I. properties, to provide similar or en-
hanced properties in UV coatings will
be explored.CW
References
(1) Van Remortel. S., Ratcliff.
R. “Ultrafine Nepheline as a Durable
and Transparent Additive to Accelerate
Radiation Cure. Rad Tech, May 2010.
(2) NIST Chemistry Webbook,
NIST standard reference database number 69, webbook.nist.gov/chemistry.
( 3) Ethylene has vibrational modes
at 835 cm-1 and 1413 cm-1 due to H-C-H
in-plane rocking and H-C-C in-plane
scissoring, respectively.
This paper was presented at
Rad Tech 2016, Chicago, IL.
Figure 13. Pareto charts for 800-810 cm-1 (top) and 1400-1410 cm-1 (bottom).
Figure 14. Cost analysis of UV-Cure PUD coating vs. filler loading level.
