Preparation and properties of thermally moulded and cast lignosulfonates starch blends

Films were prepared from wheat starch and crude commercial lignosulfonates in presence of glycerol, either by thermal moulding or by casting. Moulded films are compared to standard plasticized starch films through their mechanical properties and their behavior with respect to water. Stress-strain mechanical tests show that incorporating 10% lignosulfonates modifies the tensile resistance of plasticized starchy films (ultimate stress decreases of a factor three and elongation at break increases of a factor two), independently of the composition of the lignosulfonates. Above 10%, distinct mechanical behaviors are observed between calcium and sodium lignosulfonate based films. Dynamic mechanical thermal analysis reveals a single grass transition temperature ranging from 16-40 degrees C as a function of lignin content. (C) 1997 Elsevier Science B.V.