When proceeding to wet-spinning, I occasionally observe lump formations within the produced fiber, like knotted rope. It distorts the overall fiber, which can be easily detected in SEM images.
My set-up is simple, and is direct reproduction of many papers in literature, where:
- coagulant liquid is stored in 4°C
- pump system is present in vertical position with syringe
- syringe is filled with polymer solution
- after the pumping starts, and fibers start flowing through needle, the beaker that holds coagulant solution is gently rotated to capture the fiber falling.
My question is this: Is there any major step that I'm missing, or are there any modifications that could possibly eliminate the knot formation and produce a continuous fiber?
Many factors for formation of beads. of which homogeneity of the polymer solution is critical.
We too observed a periodic bead formation in electrospun cellulose nano-fibers.. and overcame it by decreasing the concentration and homogeneity of the solution.
What you suggest is to decrease the polymer concentration, isn't it? But in literature it is done at 15%w/v. If we decrease it, we would not be able to reproduce the results, would we?
But if we would stir the solution for more hours, we can get a more homogenuous solution. I'd give if it a try, thank you.
Try the usual suspects, voltage, distance to solution surface, needle gauge, flow rate keep ambient temperature and humidity as constant as you can. If you screen through the variables that you can, I doubt you will have to play around with solvents, even at 15% w/v. Make sure the coagulant solution itself is the only ground, and that the ground is functioning well. Make sure PCL is dissolved on stir plate for at least 24 hours before use.
I've already started for those trials, since it doesn't seem to have so much differences with respect to research papers done on the topic. I surely would at last find a best pick.
Do you suggest these for testing? To test whether any of the steps in procedure should be changed? My problem is with polymer solution flowing through the needle tip. If I decrease my polymer concentration by two folds, I don't even get the fiber formations. And if I would fill syringe with only solvent, why bother doing wet spinning...
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