Vidal-Urquiza, Turner K.

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    Synthesis and thermomechanical characterization of calcium alginate polymer films
    (2013) Vidal-Urquiza, Turner K.; Perales-Pérez, Oscar J.; College of Engineering; Valentín, Ricky; Quintero, Pedro; Department of Mechanical Engineering; Ortiz-Albino, Reyes
    In the present work, the precise characterization of structural and thermomechanical properties of alginate films was evaluated. For this aim, sodium alginate films crosslinked with divalent Ca2+ and Ba2+ ions were synthesized via an immersion technique, in which the solution concentrations and immersion times were controlled. By this technique, sodium alginate films were placed in contact with aqueous solutions at different concentrations (0.1M, 0.15M and 0.2M) for Ca ions and (25mM, 50mM and 75mM, 0.1M, 0.15M, 0.2M) for Ba ions, under a range from 0.5 to 96 hours of immersion times, respectively. X-ray diffraction, Fourier-transform infrared and Raman spectroscopy techniques confirmed developing structures the calcium alginate and barium. Thermogravimetric analysis (TGA) performed under a nitrogen atmosphere, helped to assess the thermal degradation and find out some temperature ranges in which these films could be used. The thermomechanical analysis (TMA) allowed the study of creep behavior of alginate films under tension loads of 0.1N, 0.25N and 0.5N at 150 °C for 75 minutes. This contributed to a slight variation in strains of alginate films. In this analysis was also observed that the calcium solution produces films with less resistance to deformation than the precursor films, compared with barium solution that produced an opposite effect. TMA analysis of the alginate films with a controlled temperature program from 25 °C to 150 °C at a heating rate of 5°C/min with same constant tensile loads. Showed a slight increased of transition temperature (Tg) when increase the multivalent cations in the precursor film. This slight upward trend in Tg was attributed to the high sensitivity of the polymer to volumetric expansion, in response to temperature change.