Controllable Preparation And Crosslinking Of Polyvinyl Alcohol Nanofiber

In the past ten years,electrospinning technology has become an important method for preparing nanofibers due to its advantages of easy fabrication,continuous preparation and abundant fiber types.As people continue to pay attention to environmental protection and green production,waterborne nanofibers have received more and more attention from academia and industry.Polyvinyl alcohol（PVA）has become one of the most widely used water-soluble polymers in electrospinning due to its good adhesion,oil resistance,degradability and biocompatibility.However,there are a large number of hydrophilic hydroxyl groups in the PVA molecular chain,resulting in a strong hydrophilic PVA.Untreated PVA has a large swelling degree in water,and swelling defects will limit the application range of PVA,so it is necessary to cross-link PVA.Commonly used crosslinking agents have biological toxicity or need to be dissolved in organic solvents,which will affect environmental safety.In this paper,water-soluble cross-linking agent EH and water-based blocked isocyanate（BI）were used to cross-link PVA nanofibers.The temperature and humidity changes in the spinning area were controlled by a self-made constant temperature and humidity system,which prevented the influence of environmental factors on the fiber morphology.On this basis,the effects of spinning voltage and injection speed on fiber morphology were investigated by scanning electron microscopy（SEM）.The effects of the type and amount of catalyst,the type and amount of cross-linking agent,and the post-treatment temperature and time on the cross-linking effect were explored through the determination of solubility and SEM.The particle size change of Na₂CO₃/Na HCO₃/PVA mixed solution was explored by nanoparticle size analyzer.Using Fourier transform infrared spectrometer,X-ray diffractometer,thermogravimetric analyzer and other characterization methods,the structural changes of cross-linking agent EH and BI cross-linked PVA nanofibers were discussed.Using Fourier transform infrared spectrometer（FT-IR）,X-ray diffractometer（XRD）,Thermogravimetric analyzer（TG）and other characterization methods,the structural changes of cross-linking agent EH and BI cross-linked PVA nanofibers were discussed.The stability of spinning solution was measured by multiple light scattering instrument.Field emission electron microscopy（FE-SEM）,X-ray photoelectron spectroscopy（XPS）and X-ray energy dispersive spectrometer（EDS）were used to investigate the distribution of crosslinking agents in PVA nanofibers.The results showed that the cross-linking agent EH has excellent cross-linking effect on PVA,and the Na₂CO₃/Na HCO₃ compound system has a great improvement in the cross-linking effect of the cross-linking agent EH.The Na₂CO₃/Na HCO₃ compound system can destroy the aggregate structure of PVA molecular chain and reduce the average particle size of PVA solution while improving the utilization rate of EH.BI also has a good cross-linking effect on PVA without using a catalyst.The PVA/BI mixed solution will appear delamination if it is left standing for a long time,and the stability is obviously lower than that of the PVA/EH mixed solution.Compared with EH,BI will be more distributed on the fiber surface.