Dear Parikshit,

Viscosity of spinning solution is very important. To evaluate the spinnability of your solution, the nature of the polymer and the molecular weight are important in order to determine the lower spinable concentration. Please give us more details about that.

Regards,

Nabyl

Every polymer solution, weather natural or synthetic varies with molecular weights and the ideal flow rate, volatage and distance is something that you might need to optimize yourself. 

I would suggest try different parameter it takes time to do it, but once done is quite handy as you can then use it for good. 

And what polymer are you using? this will be helpful in telling you more parameters about electrospinning it

Regards

Saad

Dear Parikshit,

Using low viscosity polymer solutions you need to keep in mind that you may have an electrospraying process, rather than electrospinning. All ideas above are true. You need to find the appropriate parameters yourself, also because of possible differences in the electrospinning setup (differences between e.g. your and mine setup) - this is why we can not help you. If it is necessary for you to have this low viscosity I suggest low feeding rate and than playing with voltage. But still, you can have particles or beads on the string, rather than fibers.

Best regards,

Michał W.

Thanks a lot everyone for the valuable suggestions....

Dear Nabyl and Saadi, I am using PAN composite....

Dear Michal, thanks a lot ....

I used aqueous solution of natural polymers and face the problem of very low viscosity (~1cP).  Its hard to control the droplet and bead formations. I suggest to use highest possible  voltage (Minimum 30 kV), target distance minimum (e-g  6 cm or less); the idea is to increase kV/cm, and slow flow rate will help; in addition, using various gauge of needles may help. Can I know what is the solvent?

highly volatile solvent will help and if its water for example, it will not evaporate before hitting the target and flat fibre could be the result instead of round cylindrical. 

look forward for your feed back regarding these tips, best wishes

Dear Parikshit,

I was working with PAN/SBA15, PAN/MMT and PAN/CNT composite dissolved in DMF, you can download the publications on RG. The Mw of the PAN was around MW = 150,000 g/mol supplied by Sigma–Aldrich, and the minimum concentration to obtain nanofibers is 7%, by using higher Mw you can spin with 4%wt.

Regards,

Nabyl

From my understanding, the viscosity is quite important parameter for electropsinning when take in conjunction of the polymer chain. You would need the jetting of Taylor cone such that the polymer chain are continuously drawn. And the continuously drawn chain  from the polymer fiber. If this fails to happens, once the polymer chain are free from the cone area and there is not entanglement with another chain to draw, then you will see the classical defect bead formation, varying diameter zone (single fiber itself will have varying diameter), excess solvent trapping ( when chain recoil, they will have tendency to conform such that it will have certain degree of solvent). To fine tune at a given viscosity, you will have to play with changing of potential,  working distance and flow-rate.

Remember, technically there is no low viscosity issue with electropsinning, its just that for a given viscosity if you are unable to draw fibers over the range of the above three parameters then there is not sufficient polymer chains. I say this cos if one searches literature he will fine people have also studied the effect of the solution of the feeding solvent in function with the above three parameters. And changing the temperature changes the viscosity,

Dear Parikshit,

My experiments showed that PAN (Mw150,000) concentration between 7 to 12 % in both DMSO and DMF solvents, leads to uniform fibers without beads. However, if you still encountering a problem with electrospinning PAN, you can refer to the paper in my RG. Also, take a look at the attachment. Hope it helps.

Regards,

Maziyar 

It is often impossible to spin at very low viscosity however this value is solution dependent.  In my experience different solvents allow adequate spinning at noticeably different viscosities.  Electrospinning is as much a balance between viscosity and surface tension effects.  If you could reduce the surface tension of your solution enough you may be able to spin with a low viscosity.  If it is not for medical purposes try adding a surfactant (such as a detergent), however bear in mind that this may be incorporated into your final polymer.