| Polyvinylalcoho/polyacrylic acid (PVA/PAA) semi-interpenetrating polymer network (SIPN) membranes have been synthesized by in situ polymerization of acrylic acid monomer in the presence of PVA, with ammonium persulfate (APS) as initiator and N,N'-methylene bisacrylamide (MBA) as cross-linking agent.The structures of the resulting semi-interpenetrating polymer network (SIPN) membranes were characterized by FT-IR, it showed that the O—H of PVA and C=O of PAA were shifted to low frenqucy, which indicated that strong hydrogen bonding between—OH of PVA and—COOH of PAA. The SIPN membranes were characterized by DMTA, it showed that there was only a peak, which was between the Tg of PVA and PAA component. Moreover, the micromorphology by TEM indicated that SIPN structures have been formed. From discussion above, it showed that good compatibility exists between PVA and PAA.The influence of varing both PVA/AA ratio and crosslinking agent ratio on the properties of the SIPN membrane were also investigated. The results showed that, when the mass ratio of PVA and AA was 80:20 or 70:30, the molar ratio of cross-linking agent was 0.3% or 0.5% or 0.7% of monomers, and the mass ratio of initiator was 0.5% of monomers, PVA/PAA mixed solution showed good film-forming properties.The above PVA/PAA mixed solution were coated on PET membrane easily, and the coating was flat and smoothly. It also found that the optic capacity of the SIPN membranes was good.Meanwhile, the hydrophilic and water-resistance properties of the SIPN membrane were also investigated. In the vast majority of cases, the water static contact angles of the SIPN membranes were lower than 30 degrees. When the mass ratio of PVA and AA was 70:30 and the molar ratio of cross-linking agent was 0.7% of monomers, and the mass ratio of initiator was 0.5% of monomers, the water static contact angle was the lowest, about 23 degree; The dissolving ratio and swelling ratio of the SIPN membranes were found to be lower than those for either pure PAA or pure PAA membranes. When the mass ratio of PVA and AA was 70:30 and the molar ratio of cross-linking agent was 0.7% of monomer, and the mass ratio of initiator was 0.5% of monomers, the resulting SIPN membranes remained integrated and non-tacky after being immersed for more than 30 d in water with temperature in the range 25-55℃, which is indicative of good water-resistance. Moreover, With the increase of cross-linking agent ratio, the heat-treatment temperature and the heat-treatment time, the adhesive bond between the coating and the PET membrane became stronger, which showed good water-resistance of the coating. |
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