Working on a project to formulate polyurethane with different cross-link density. Is there any quick method to know if two polymers have same cross-link density. I know methods to calculate cross link density but they are time taking. Numeric value of cross-link density is not required here.
Thank you.
Raviteja Kommineni.
As afist approach you could compare the modulus values above tg from a DMA-measurement. This should give you an indication if the materials are comparable (same or better no filler, no plasticizer etc.).
In your case where you try to compare differently crosslinked polyurethane this should give you a value proportional to crosslink density.
The measurement can be done (depending on the required temperature range) in 1 to 3 hours. I don`t know whether this counts for you as time consuming or not.
best regards
Matthias Jaunich
Thanks Matthias for your answer. I was thinking of this already and this is the best option available. I was just curious if any test like MEK rub or pendulum hardness will give an indication of how comparable crosslink densities are in a quick fashion. For DMA, getting perfect film of constant thickness and without defects is very challenging.
Raviteja,
Equilibrium swelling studies may allow qualitative comparisons, as Tihomir suggested. It may be valuable to note any soluble/extractable fractions from the networks. This can be as simple as recording difference between original sample weights and dried weights after solvent exposure.
Good luck!
Equilibrium swelling or/and Young Modulus could be useful to compare crosslinking density, but also DSC determination, could be an answer of crystalinity change due to crosslinking, crosslinking decrease crystallinity and increase Tg.
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