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On the electrospinning of PVB solutions
Švrčinová, Petra ; Filip, Petr ; Lubasová, D.
Extension rheological characteristics belong to the principal description of polymer jet formation during a process of electrospinning. However, in spite of nearly absence of shear deformation of polymer solutions during the process of their spinnability, it seems that shear electrorheological characteristics can serve as an indicator of good or bad quality of an electrospun template. The experiments were carried out with four polyvinylbutyral (PVB) solutions in concentration of 10 wt%. Shear viscosities in absence (η0) and presence (η) of electric field were measured using a rotational rheometer equipped with an electrorheological cell. It was shown that the good solvents of PVB exhibit an almost constant curve of η/η0 vs. electric field strength, whereas the viscosity curves for the poor solvents exhibit enhancement. This enhancement corresponds to better quality of electrospun templates (obtained for polymer solutions of PVB with poor solvents).
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On behaviour of PVB solutions in electrospinning
Švrčinová, Petra ; Lubasová, D. ; Filip, Petr ; Martinová, L.
Electrospinning produces nanofibre sheets from polymer solutions under high electric field. Rheological properties of these solutions play a substantial role in a nanofibre formation simultaneously with properties of polymers and solvents applied. This contribution aims at a determination of dependence of shear viscosity of polyvinylbuthyral (PVB) on the intensity of electric field to which PVB solutions are exposed. PVB was dissolved consecutively in a series of solvents as 10% wt. solution. It was found that the viscosity ratio (viscosity of a solution in presence of electric field/viscosity of a solution in absence of electric field) depends on the polarity of solvent. This pre-determines the possibility of application of the individual solvents for the process of electrospinning.
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A note to the measurement of extensional viscosity using SER Universal Testing Platform with different shapes of polymer samples
Švrčinová, Petra ; Filip, Petr ; Kharlamov, Alexander
For polymer melts, with respect to their numerical simulations, there were recommended to apply polymer samples (rectangles) with a width not exceeding 8 mm and a thickness less than 0.4 mm. The aim of this contribution is to document - for material used (LDPE Escorene, Exxon, USA) - the invariantness of the elongational viscosity measured with respect to sample dimensions including its width and thickness. The width of the samples used consecutively attained 12.7, 11.0, 9.3, and 7.4 mm; the thickness also ranged across a sufficiently broad interval (0.3-1.1mm). Temperature was set to 180, 190, and 200oC. For the measurements there were used the SER Universal Testing Platform from the Xpansion Instruments; the model SER-HV-P01 was applied with a Physica MCR501 rotational rheometer host system. The results obtained justify usage of a 'classical' width 12.7 mm (1/2") more suitable for better manipulation with a sample, especially its fixing to both drums perpendicularly to the clamps.
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