Influence of Polymer Relaxation Time on the Electrospinning Process: Numerical Investigation.

"Electrospinnability", or the ease with which a solution can be used to obtain bead-free uniform fibers, depends on a large number of parameters, including solution properties, process parameters and ambient conditions. In this study, the effect of the polymer relaxation time on electrospinning of dilute polymer solutions is investigated numerically. It is shown that elastic stresses (ES) increase exponentially with the Deborah number ( D e ). For each polymer concentration there exists a critical D e below which the ES are insufficient to overcome capillary stresses (CS) and lead to the formation of beaded fibers. However, above the critical D e , there is a higher probability of the ES overcoming the CS and leading to the formation of uniform fibers. This analysis suggests the possibility of improved electrospinnability even with dilute polymer solutions, provided the relaxation time is sufficiently large. It is also found that changes in the drag coefficient due to change in the polymer conformation and self-concentration of polymer molecules would become significant for the electrospinning of polymer solutions with a longer relaxation time and high conductivity.