Identificador: TDX:3015
Autores: Colace, Gianmarco
Resumen:
Poly(vinyl alcohol) (PVA), a polyhydroxy polymer, is the largest volume, synthetic water-soluble polymer produced in the world.
The excellent chemical resistance and physical properties of PVA resins have resulted in broad industrial use. Poly(vinyl alcohol) films exhibit high tensile strength, abrasion resistance, and oxygen barrier properties which under dry conditions are superior to those of most polymers. PVA films are broadly used in packaging applications, where permeability became a critical property to evaluate. A wide range of modifications can be applied to change the moisture diffusion through the film; two types were chosen for the work: blending with other water-soluble polymers and preparation of a composite.
According to Robeson, a series model of polymeric matrix and particles, leads to a tortuous system, which, for a given thickness, decreases the permeability, meanwhile Bharadwaj models for blended polymer were used for permeability prediction. The film casting is based on solvent evaporation: the polymer is dissolved and forms a solution with a certain concentration and viscosity; then the particles or the second water-soluble polymer are loaded in the system; the viscous mixture is poured on a glass support and spread across it manually with a casting knife set at different gaps. So, the wet film is left to stand to evaporate the solvent and leave a dry film. Solubility experiments were performed, by measuring the dissolution time of the film, and it was not significantly influenced by the material modification. Dry cup method experiments were run to measure the water vapor permeability, recording a decreasing values of permeabilities.
Repositori URV