Electrospinning PVA solution-rheology and morphology analyses

Abstract

This study investigates the electrospinning (ES) of poly(vinyl alcohol) (PVA). All of the electrospinning process or property parameters, including the concentration effect, the molecular weight effect, the pH effect, the salt effect, electrode voltage, surface tension, shear viscosity and extensional viscosity were examined. The pH variation had an insignificant effect on the formation of fibers. An increase in electrode voltage and salt concentration negatively affects the ES process. The salt concentration that yields an acceptable ES membrane without droplets was below 0.001 N. Also, the decrease in elongation viscosity rather than the variation in electric conductivity or surface tension was the main cause of the negative effect on the fiber formation when the salt was added to a PVA solution. The salt negative effects follow the order CaCl2 < NaCl < NaI < KBr < KI. Experimental results show that the ES processability of PVA solution depends mainly on the concentration and secondly on the molecular weight of the dissolved polymer. The PVA solution prepared with a larger molecular weight had a lower concentration window in the ES process. The concentration window of PVA solution with an MW of 88,000 in the ES process ranged between 6 and 14 wt%. Additionally, experimental results demonstrated that the upper limitation on PVA concentration depends strongly on the extension viscosity of the spun solution. Whenever the power law index n determined by extension test exceeds one, spinning is unfeasible, regardless of whether the index of the power law for shearing is within the normal range. Briefly, this work indicates that the extension viscosity can be adopted as a good indicator for predicting ES processability.