Study On The Blow Molding Processing Of PVA And Properties Of Its Product

Poly (vinyl alcohol) (PVA) is one of the most popular water-soluble synthetic resins, with many excellent characteristics, such as good barrier properties to organic solvent and oxygen. Therefore, PVA has particular advantages in packaging and transportation applications of organic solvent. However, PVA has a large number of hydroxyl groups, forming many inter- and intra-molecular hydrogen bondings, which make its melting point close to its thermal decomposition temperature and its melt-processing very difficult. Industry application of PVA is usually based on wet process, limiting the application of PVA. It would be surely a great progress in the application fields of PVA if the melt-processing of PVA can be realized and the barrier container of PVA can be obtained.Based on the realization of the thermal blowing and melt spinning of PVA through intermolecular complexation, the uniform and transparent PVA containers with excellent mechanical and barrier properties are obtained by further optimizing the components of modified PVA and the parameters of extrusion, which enlarges the application of PVA. The rheological properties, die swell and the flow instability of modified PVA melt are studied, and the mechanical properties of modified PVA parison are studied considering the effect of the content of plasticizer, blowup ratio, the time and temperature of heat treatment. The results show that at the testing shear rates, the modified PVA melts are pseudo-plastic fluids and suitable to extrusion blow molding. The melt apparent viscosity decreases with the increase of the plasticizer content, viscous flow activation energy decreases with the increase of shear rate and water content, and the effect of Ac on the shear sensitivity of PVA is more obvious than that of water. The increase of the Ac content decreases the extruding elasticity of the modified PVA melt, thus inhabites the parison swell. The incorporation of Ac to modified PVA appears to improve the flow instability and increase the dimensional stability of the product. Heat treatment improves the crystallization of PVA blown parison, i.e. enhancing its crystllinity and mechanical properties. Certain blowup is beneficial to the orientation of PVA blown parison and increases its tensile strength.