We are electrospinning PVA solutions of 2 kinds.
-Partially hydrolyzed PVA (70-80% hydrolized)
-Completely hydrolyzed PVA 99-100%
Working at 2 concentrations 7% and 11%, since we can only electrospin in a range od 6-12% m/v lower than 6% is too diluted and sprays, over 12% it'll be too viscous to go through the syringe.
Molecular weight in a range of 70.000-100.000 Daltons.
We tried different voltages and distances: voltages of 10KV, 12KV and 15KV, and distances of 10cm, 15cm and 17cm. flow rate always fixed at 1ml/h and electrospinning time is 10 minutes.
But no matter the combinations of distance and voltage we use, we are mostly obtaining some wobbly entangled fibers and very few of them are straight electrospun fibers.
Most of the experiments look like the first picture I uploaded, except the mixture of 7%m/v PVA fully hydrolyzed which for some reason no matter the voltage or distance it keeps giving us a thin electrospray like in the second picture, 11%m/v PVA fully hydrolyzed gave us fibers but they were shorter and still had the same issue of most of them looking entangled.
I would really appreciate if someone has a suggestion on how to tackle this issue.
Dear Santiago Sarasola, you didn't mentioned the solvent! The last part of the question statement details gives the reason, the low degree hydrolyzed samples are not perfectly solubilized, so either you use another good solvent or to slightly reduce concentration. My Regards
Dear Abdelkader BOUAZIZ Abdelkader Bouaziz, sorry seems I forgot to clarify that detail.
Since all mixtures we are using are of different types or concentrations of PVA, we are always using water as solvent.
after mixing the PVA with water, we put them on a shaker for 24 hs at 60°C and 200 rpm, then we gave them a final mix with a magnetic mixer at 80°C 300 rpm for 10 minutes (it starts to form bubbles after a few minutes, and if we don't remove the samples from the mixer quickly, it'll spill out all over the shaker).
Hope this information is enough. My regards.
Santiago Sarasola looks like in the second picture you are getting some fiber morphology already (or say beaded fibers). Fibers are present in nanometer range, difficult to locate via normal microscope, SEM will reveal a clear picture.
Regarding the wobbling fibers, I go for lower flow rate and not too high concentration. Hope this helps.
Dear @Ankit Mishra we were using 7% and 11% but we already discarded the 7 % ones since we were only obtaining that continuus pattern of little fibers or sprayed droplets, and we want long fibers like the ones in the first picture, problem is it looks all curled up on itself and we'd like to obtain long straight stretched fibers rather rhan those messy wobbly entangled ones
Regarding of flow rate, my postrgrade tutor said we they've been obtaining fibers with 1 ml/h for a while and we probably shouldn't change it, but you say that flow rate is too high? If you can give me more context on what flow rate you'd be using for this kind of concentrations and water soluble polymers I'd really appreciate it and maybe I can convince my tutor that a different flow rate might be necessary.
Best regards, Santiago.
Centrifugal electrospinning device should be used to obtain straight and ordered fibers.
In a traditional electrospinning device, fibers entering the "Whipping motion" make a spin movement, distributed and intertwined fibers are formed.
In addition, some polymers are prone to forming straight fibers, such as polycaprolactone.
- Badges
- Science topic