Plasticity of hot air-dried mannuronate- and guluronate-rich alginate films

The plasticity of hot air-dried guluronate-rich (MG) and mannuronate-rich (MC) alginate films prepared from 2% and 4% (w/w) alginate solutions, which contained the same amount of polymer, through hot-air drying at 40–80 °C were investigated. These films were subjected to thermomechanical, differential scanning calorimetry, fourier-transform infrared, X-ray diffractometry, dimension, morphology, moisture content, viscosity and polymer molecular weight analysis. Film plasticity increased when dilute alginate solution and MC were employed in film preparation. This was due to decrease in polymer–polymer interaction at high-strength domains of matrix involving C–H, O–H, C–O and/or CO moiety of alginate, attributing to plasticization effect of water and ease of molecular rearrangement of alginate. The plasticity of film decreased with an increase in drying temperature from 40 to 60 °C following heat-induced polymer–polymer interaction. A further increase in drying temperature to 80 °C nonetheless greatly promoted film plasticity through air bubble formation and reduced alginate molecular weight in film.