TY - JOUR
T1 - Viscoelastic electrospun jets
T2 - Initial stresses and elongational rheometry
AU - Han, Tao
AU - Yarin, Alexander L.
AU - Reneker, Darrell H.
N1 - Funding Information:
We acknowledge the financial support from the National Science Foundation, DMI-0403835-2 (NIRT), NSF subcontract 25-1110-0038-002 (Nebraska DMI-0600733), and a subcontract through Ohio State University, NSF EEC-0425626 (RF 60002999). The Coalescence Filtration Nanomaterials Consortium of the University of Akron provided financial support and an industrial point of view. The authors thank Dr. Daniel Galehouse for the design and construction of a laser velocimeter, and Mr. Steven Roberts for technician support. DHR and TH thank Apogee Technology Inc. for financial support. ALY also acknowledges partial support of this work by the National Science Foundation under Grant NIRT CBET-0609062.
PY - 2008/3/17
Y1 - 2008/3/17
N2 - A novel method of characterization of viscoelastic longitudinal stresses in electrospun jets of semi-dilute and concentrated polymer solutions and melts is introduced. The measured longitudinal stresses at the beginning of the thin jet region in the jets of a 6 wt% aqueous solution of polyethylene oxide (Mw = 400 kDa) were of the order of 100 kPa, which is two orders of magnitude larger than in any other free viscoelastic jets issued from nozzles and orifices. This is attributed to elongation-driven stretching of polymeric liquids in the transition zone, between the preceding modified Taylor cone zone and the beginning of the thin jet region, where the stretching rates are of the order of 100-1000 s-1. The Rouse relaxation times found were in the range of 3-8 ms, and the moduli of elasticity were of the order of 100 Pa. A novel explanation of the reasons for the formation of the straight sections in the electrospun jets is proposed. The straight sections are stabilized by the high initial longitudinal stresses in the jet generated due to strong electrically driven stretching in the transition zone. The further electrically driven stretching in the jet (after the transition zone) is relatively weak, and viscoelastic Rouse relaxation prevails. The relaxation distance of the longitudinal stresses along the jet increases with the applied voltage (which generates higher initial stresses in the transition zone) and thus the length of straight section of the jet should increase as the applied voltage increases. The results also point at an opportunity to develop an elongational rheometer for concentrated polymeric systems with stretching rates of the order of 100-1000 s-1. The proposed rheometer employs excitation of electrically driven jets by single lateral pulses, and observation of the pulse propagation and widening along the jet. This reveals the level of the longitudinal stresses along the jet and allows evaluation of the viscoelastic Rouse relaxation time, modulus of elasticity and the elongational viscosity in the jet.
AB - A novel method of characterization of viscoelastic longitudinal stresses in electrospun jets of semi-dilute and concentrated polymer solutions and melts is introduced. The measured longitudinal stresses at the beginning of the thin jet region in the jets of a 6 wt% aqueous solution of polyethylene oxide (Mw = 400 kDa) were of the order of 100 kPa, which is two orders of magnitude larger than in any other free viscoelastic jets issued from nozzles and orifices. This is attributed to elongation-driven stretching of polymeric liquids in the transition zone, between the preceding modified Taylor cone zone and the beginning of the thin jet region, where the stretching rates are of the order of 100-1000 s-1. The Rouse relaxation times found were in the range of 3-8 ms, and the moduli of elasticity were of the order of 100 Pa. A novel explanation of the reasons for the formation of the straight sections in the electrospun jets is proposed. The straight sections are stabilized by the high initial longitudinal stresses in the jet generated due to strong electrically driven stretching in the transition zone. The further electrically driven stretching in the jet (after the transition zone) is relatively weak, and viscoelastic Rouse relaxation prevails. The relaxation distance of the longitudinal stresses along the jet increases with the applied voltage (which generates higher initial stresses in the transition zone) and thus the length of straight section of the jet should increase as the applied voltage increases. The results also point at an opportunity to develop an elongational rheometer for concentrated polymeric systems with stretching rates of the order of 100-1000 s-1. The proposed rheometer employs excitation of electrically driven jets by single lateral pulses, and observation of the pulse propagation and widening along the jet. This reveals the level of the longitudinal stresses along the jet and allows evaluation of the viscoelastic Rouse relaxation time, modulus of elasticity and the elongational viscosity in the jet.
KW - Electrospinning
KW - Elongational rheometer
KW - Elongational stress
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U2 - 10.1016/j.polymer.2008.01.035
DO - 10.1016/j.polymer.2008.01.035
M3 - Article
AN - SCOPUS:40249104584
VL - 49
SP - 1651
EP - 1658
JO - Polymer (United Kingdom)
JF - Polymer (United Kingdom)
SN - 0032-3861
IS - 6
ER -