Research On Preparation And Filtration Performance Of Water-Resistant Polyvinyl Alcohol Nanofiber Mats

Recently, Electrospinning has become an important method in fabricating of nanofibrous structures. Non-woven fabrics are used as substrates to receive polymer nanofibers, and in this process nanofiber mats are formed. Compared to traditional nonwoven fiber mat, nanofibrous mats have many advantages, such as light weight, high specific surface area and good protection, so that nanofibrous mats have extensive application prospects in the filtration, thermal insulation, protection and so on. PVA is the main electrospun material with excellent physical properties, biodegradability, good mechanical properties in the dry state, and many other advantages such as low price and easy to get, etc. However, PVA has a poor water resistance result from a large number of hydroxyl groups in molecules which limits its application. So, PVA was modified to achieve water-resistant PVA nanofiber mats, which can broaden the application of PVA nanofiber mats especially the application of filters.Methods of improving the water resistance of PVA can be divided into physical modification and chemical modification. In this paper, the method of chemically modified by other agents was studied.Urea, oxalic acid(OA), maleic acid(MA), and glutaraldehyde(GA) were chosen to modified PVA solution firstly.The results showed that the spinnability of PVA modified by urea was good but the prepared mat was water-soluble; the spinnability of PVA modified by OA or MA was bad which can not be used in electrospinning; PVA can be reacted with GA directly but the gelation make electrospinning impossibility.Then, the PVA nanofiber mats were prepared by electrospinning and immersed in a given concentration of GA(25% aqueous solution)and trace HCl in acetone solution.The effect on water resistance of PVA was discussed by selected different concentrations of modified solution under different modification time, then characterized by Scanning Electron Micrograph (SEM) and Fourier Transform Infrared (FTIR) spectrometry. The resulting crosslinked PVA substrates showed excellent water resistance,and the variation of time had little effect on the crosslinking reaction while the concentration of GA had greater impact.On the base of successful preparation of water-resistant PVA nanofiber mats,in this study, 12 different concentrations of GA (50% aqueous solution)in acetone solution were employed to modify 88% PVA and 95% PVA nanofiber mats,the modified effect were studied systemic by the integration of visual sensory evaluation and water durability measurements firstly. The results showed that the modified effect of two different PVA nanofiber membrane were good. SEM and FTIR were employed to characterize the better nanofiber mats, as well as the mechanical, thermal stability and crystallinity changes were analyzed.The filtration performance of 5% GA modified PVA nanofiber mats was studied, and results showed that the average pore size of nonwoven substrate was about 112μm, while the largest average pore size of PVA nanofiber membrane was only 3.37μm, and the pore size distribution of nanofiber membrane was more concentrated, indicating that the attachment of nanofiber membrane effectively reduce the pore size of substrate material. The water-resistant PVA nanofiber mats exhibited a high flux rate and an good rejection rate. In addition, Ethanol as solvent, different concentrations of GA modified solution were prepared, and the modified results showed a good effect and a better experimental environment.