Hi all,
I'm comparing the curing times of two coatings subjected to UV irradiation in rheology. To do this, I'm working with constant dynamic mechanical conditions: f = 1 Hz, strain = 1 %.
During curing, I observe a transient increase in viscous modulus G'' (see graphs attached). How can I explain this G'' overshoot? Is the measurement valid?
I have carried out tests imposing a normal force (Fn = 0 N) during the measurement, and tests without imposing normal force. The transient increase in G'' occurs in both cases.
Thanks in advance!
Dr. Lucie Laporte
It is interesting question . I attached below the link for the article published by the Gavin J. Donleya , Ea tal. They investigate the overshoot in loss modulus seen in materials that yield. They show that this phenomenon is caused by the transition from primarily solid-like, viscoelastic dissipation in the linear regime to primarily fluid-like, plastic flow at larger amplitudes. They compare and contrast this with a viscoelastic liquid with no yielding behavior.
Hope the article content is helpful for you to stand on the whole story.
Best regards
https://pmc.ncbi.nlm.nih.gov/articles/PMC7486776/pdf/pnas.202003869.pdf
Dear Lucie,
Please see our paper, where similar behavior was observed, which is discussed on page 2370. G'' reaches a maximum at the glass transition temperature.
All the best with your research and with best regards,
Paul
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