Abstract
The aim of this research was to survey all possible combinations of cornstarch (S), lignosulfonate (LS), and glycerol (G) that may be used in preparing thermally molded thermoplastics. A ternary diagram was developed to define the best range of compositions for production of these thermoplastics in accordance with ASTM D 638-M. Dynamic mechanical analysis technique (DMA) revealed more than one glass relaxation, influenced by glycerol content. In stress—strain tests, incorporation of LS decreased the stress and increased strain considerably, in comparison with their respective S—G matrices. The total amount of water absorbed by the specimens increased proportionally to relative humidity (RH) and glycerol content. An increase in LS content requires longer time to reach steady state for the absorption process. Moreover, the diffusion coefficient of water in the thermoplastic rose significantly with the amount of glycerol. However, the diffusion coefficient results did not show a simple, monotonic relation with the values of RH or with absorbed water content.