Plasticity of hot air-dried mannuronate-and guluronate-rich alginate films for application in transdermal drug delivery system / Noor Shimariza Ashikin Wan Hussin

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 to 80°C were investigated. These films were subjected to thermomechanical, differential scanning calorimetry, Fourier-transform infra-red, x-ray diffractometry, dimension, morphology, moisture content, viscosity and polymer molecular weight analysis. The water weight loss profile of alginate solution undergoing drying was recorded with time. The polymer weight of all solid films was kept constant. 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-0 and/or C=0 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. Drying of dilute alginate solution or at low drying temperature was accompanied by both constant rate and falling rate periods. The falling rate period dominated in drying of alginate solution of high polymer concentration and at high drying temperatures with internal diffusion being the governing transport phenomenon for water. Drying process of 4% (w/w) alginate solution at 60 and 80°C was relatively simple as there was only a single drying stage. Nonetheless, it could give rise to different product plasticity's in spite of being convenience with respect to process control.