Study On Modified Pva Coating Solution Used In Flexible Packaging

As a high barrier material for packaging, modified PVA coated films are being paid more attention for its lower cost and degradable properties. In this paper, the aqueous solution of PVA1799was mixed with surfactant (acetylenic glycols) and cross-linking agent (Cymel385) to prepare a modified PVA coating solution.PVA1799was chosen for PVA coating solution. The stability of apparent viscosity of PVA1799solution was studied. Also, the surface tensions of PVA1799solution in different concentrations were tested.In an effort to decrease the surface tension of PVA1799solution so that it can wet the substrate well, three different kinds of acetylenic glycols were added to PVA1799solutions, respectively. The surface tension of7wt%PVA1799aqueous solutions with different concentrations of surfactants was determined by surface tension tester. The result shows that the surface tension value of7wt%PVA1799solutions have decreased from64.9mN/m to33mN/m when the amount of SA、PSA、S-195surfactant was added to0.05phr. Then the static contact angles of PVA1799solution with different concentrations of surfactant on BOPP film were tested, which show the improvement of wetting.In order to improve the moisture resistance of PVA layer on substrate after dried, Cymel385and phosphoric acid were used as cross-linking agent and catalyst for the PVA1799solution, respectively, to make a modified PVA coating solution. FT-IR was used to prove the cross-linking reaction between PVA and cymel385.Modified PVA films were made by casting method. The mechanical properties, oxygen permeability coefficient, water vapor permeation, equilibrium moisture absorption rate of modified PVA film were tested. The result shows that with increase of the amount of Cymel385, the tensile strength of modified PVA film increase, while the elongation at break decrease; with increase of the amount of Cymel385, the oxygen permeability coefficient of modified PVA film increases; when the amount of Cymel385is30wt%with respect to the mass of PVA resin, the oxygen permeability coefficient of modified PVA is1.46X10-16cm3·cm/(cm2·s·Pa), with a increase by4.1%. When the amount of cymel385is20wt%with respect to the mass of PVA resin, the oxygen permeability coefficient of modified PVA film almost does not increase after treatment for4hours in the condition23℃,52%RH. The Equilibrium moisture absorption rate decrease with the increase of Cymel385. When the amount of Cymel385is over20%, the equilibrium moisture absorption rate has a slight decrease, which shows that the optimum amount of Cymel385is20wt%with respect to the mass of PVA resin.Three different kinds of modified PVA coated films were made and the oxygen transmission rates of them were tested. The oxygen transmission rate of the three prepared PVA coated film are lowered to10cm3/(m2·24h·0.1MPa), which can meet the national standard for aseptic packaging material. The oxygen transmission rate of unmodified and modified PVA coated films were tested after treating in the condition of38℃,90%RH for24hours. The result shows that the modified PVA coated films have a better resistance to moisture compared to unmodified PVA coated films.