Page 50 - Market Analysis Report of Optical Communications Field in China & Global market 2018

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planning to implement a dry nitrogen purge in the future to be able to As expected, coating A, the conventional secondary coating, is more
measure surface cure as well. susceptible to oxygen inhibition, resulting in longer induction time.
3.2.1Maximum Slope of %RAU Curve Between coating B and coating C, coating B has quite shorter induction
Unlike the need for conversion in Photo DSC, % RAU in FTIR is a direct time (by about 0.7 second), suggesting that the formulation approach in
measurement of double bond conversion. Thus, maximum slope of coating B is more effective in reducing inhibition time. Despite of longer
RAU curve in real-time FTIR-ATR is also a direct measurement of peak induction time, coating C reacts faster and eventually reaches higher
polymerization rate. conversion (Plateau % RAU).
Figure 8. Maximum slope of % RAU Curve
Such insight into induction time, reaction rate, and double bond
conversion is crucial in understanding structure-property relationship in
coating development, to meet stringent requirements in high speed draw
of optical fiber manufacturing.

4.Conclusions
Due to its unique monochromatic emission, UV-LED cure is different
than conventional broadband UV. Therefore, there is a need to retrofit
laboratory analytical equipment with UV-LED light sources to conduct
cure speed measurement.
Recently, both Photo-DSC and Real-time FTIR-ATR have been equipped
Just as expected, the maximum photopolymerization rate, as measured with UV-LED light source, in DSM Functional Materials’ R&D Lab.
as maximum slope of RAU curve, indicated the same relative cure speed
among the three coatings, C>B>A (Figure 8). When measuring the cure speed of three secondary coatings with both
techniques, the same cure speed ratings were obtained, demonstrating
3.2.2Plateau % RAU excellent correlation and consistency between the two tests.
As seen in Figure 9, % RAU reached plateau after 20 seconds,
demonstrating that the reaction has taken place within 18 seconds of the Inhibition time in Real-time FTIR-ATR is a good indicator of the severity
UV-LED irradiation (Note that the lamp did not turn on until after 2 of a given coating’s susceptibility toward oxygen inhibition.
seconds). Positive results obtained in this study suggest that formulation
Figure 9. Plateau % RAU approaches in coating B and C are effective in enhancing cure responses
to UV-LED.

5.Acknowledgement
The authors would like to thank Mr. Roger Salvesen for conducting
Photo-DSC experiments, as well as Dr. Pratik Shah and Dr. Huimin Cao
for their suggestions.

6.References
[1] Permission granted to DSM Functional Materials for re- publication
in this IWCS Conference Paper © COPYRIGHT 2011 UV Process
Supply, Inc.
[2] http://en.ndrc.gov.cn/newsrelease/201612/P020161207645765
233498.pdf
And, once again, coating C reached highest % RAU, followed by coating B, [3] http://www.khmdc.cn/a/huanbaojieneng/ website
and coating A.
[4] J. A. Arceneaus, “Mitigation of Oxygen Inhibition to Improve the UV
LED Cure Process”, Radtech International North America, uv.eb
3.2.3Induction Time
Induction time is an additional piece of information from real-time West, 2015.
FTIR that is not available in Photo-DSC. [5] E. V. Sitzmann, “Critical photoinitiators for UV-LED Curing:
Figure 10. Induction Time Enabling 3D Printing, Inks and Coatings”, Radtech International
North America, uv.eb West, 2015.
[6] N. Cramer, “Effects of UV-LED Light Curing on Cure Rate and
Oxygen Inhibition”, Radtech International North America, uv.eb
West, 2017.
[7] W. Schaeffer, et. al. “Chemistry and Methods for Enhanced UV-LED
Cure Performance”, Radtech International North America, uv.eb
West, 2017.
[8] Courtesy of Phoseon Technology.
[9] P. Shah et. al. “More than 80% energy efficiency achieved in optical
fiber coatings application process using UV-LED lamps and novel
chemistries”, Proceedings of 65th IWCS Conference, 2016.
[10] P. Shah et. al. “An innovation in optical fiber manufacturing process
by UV-LED lamps and novel optical fiber coating design supporting
Induction time is the time in the beginning of (photo)polymerization both Wet on Wet (WOW) and Wet on Dry (WOD) processing at
when initiating radicals were consumed by radical scavengers, such as high speeds”, Proceedings of the 63rd IWCS Conference, 2014.
inhibitors and oxygen. [11] S. R. Schmid and A. F. Toussaint, “Chapter 4 - Optical Fiber
Coatings”, Specialty Optical Fiber Handbook
Since coatings A, B and C have similar level of inhibitors, the induction [12] http://www.rosendahlnextrom.com/ website
time is an excellent indicator of oxygen inhibition effect on the through [13] https://en.wikipedia.org/wiki/Attenuated_total_reflectan ce website
cure (as what measured is the bottom % RAU).

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