Shear and elongational rheometry for determination of spinnability window of polymer solutions in solution blow spinning

Abstract

Recently, processes for stable and efficient production of polymeric nano-and submicron fibrous materials, like solution blow spinning, have developed rapidly. However, the application of new polymers, synthetic or natural, for the fabrication of innovative fibrous materials still requires a trial-and-error approach to determine the spinnability window of polymer concentration in the solution. In this study, we investigated the use of shear and elongational rheometry to determine the spinnability window of polymer solutions of two synthetic polymers-poly-L-lactic acid (PLLA) and polyurethane (PU). Based on measured values of four polymer solution properties: density, surface tension, zero shear viscosity, and relaxation time, we calculated Ohnesorge (Oh) and Deborah (De) numbers corresponding to the polymer concentration ranges from 1 to 9%w/w for PLLA and 1-12%w/w for PU. After blow spinning each of the investigated solutions and using images from the scanning electron microscope and calculated values of Oh and De numbers, we determined the spinnability window for both polymers in the solution blow spinning process to be Oh >0.5, De/Oh >1, and Oh < 25.

Evaluation of the polycaprolactone (PCL) hydrolytic degradation in acid solvent and its influence on the electrospinning process

“…As observed in Fig. 5, these microfibers from elongated microbeads (Janus structure) with decreasing molar mass, which can be attributed to deficiencies in the viscous forces for this solution, indicating a lower geometric relaxation time for the solution [62,63]. On the other hand, in this result, the authors can see that with the increase of storage time for PCL solution an increasing number of beads appeared, as shown in Fig.…”

“…In this regime, the solution lacks the necessary viscous resistance to be deformed, resulting in the continuous jet breaking into droplets, resembling the electrospraying processes, as shown in Figure 5. In this context, it can be referenced that the viscoelastic behavior exhibits low relaxation times [44,59,62,63]. The analysis of variance (ANOVA) results presented in Table 3 revealed that the storage time of PCL solutions in acetic acid for up to 7 days had the most significant influence on the variation of fiber diameter, with a confidence level above 99.9%.…”

Electrospun Poly(carbonate-urea-urethane)s Nonwovens with Shape-Memory Properties as a Potential Biomaterial

“…These results were consistent with our observation that the PCUU at 6 wt % concentration was too viscous for the ES process to be effective. If the solution was too diluted, then the polymer fiber broke up into droplets before reaching the collector due to the effects of surface tension and insufficient overlapping of polymer molecules to the critical polymer concentration . However, if the concentration of the solution was too high, then fibers could not be formed due to the high viscosity, which made it difficult to control the solution flow rate through the capillary …”

Production of Nanofibers by Blow Spinning from Polylactide Containing Propolis and Beeswax

“…The most critical process parameters in blow spinning include polymer flow rate from the nozzle, compressed gas flow rate, nozzle diameter, nozzle-to-collector distance, and collector rotational speed [20,21]. Among the physicochemical parameters of the solution, the following are essential: polymer concentration, extensional viscosity, surface tension, and apparent viscosity [22]. The temperature and humidity in which blow spinning is carried out also affect its course.…”