Fabrication of PVDF/PVA microtubules by coaxial electrospinning
This paper presents a unique approach to fabricating poly(vinylidene fluoride) (PVDF)/poly(vinyl alcohol) (PVA) microtubules in coaxial electrospinning. This methodology includes two objectives, namely, microtubular formation and mitigation of secondary erosion. In the first step, PVDF solution and ethanol mixed PVA solution are directly electrospun to PVDF/PVA microtubules. Then, the obtained PVDF/PVA microtubules are treated by a water assisted route to remove the residual solvents and mitigate the secondary erosion. Without solvent erosion, PVDF/PVA microtubules exhibit smooth inner and outer surfaces and hollow structure. Furthermore, in this technique, the microtubule diameter and wall thickness are controllable by the feed rate of PVA solution in electrospinning. Thinner-walled microtubules are prepared under a high feed rate. Differential scanning calorimetry, X-ray Diffraction and Fourier Transformed Infrared Spectroscopy are respectively used to characterize the crystallization of PVDF. High degree of PVDF crystallinity is shown in thin PVDF/PVA microtubules. β-phase crystallite is dominant. PVDF/PVA microtubule evidently exhibits capillary action. The wicking rate of silicone oil is 8.08 μm/s, as calculated by a wicking test.