Synthesis and characterization of cross-linked starch/lignin film

A cross-linked film, based on corn starch/hydroxymethylated alkali lignin, was prepared. The effects of solution casting, pH, and reactant stoichiometries on water absorbability and mechanical properties of the starch/lignin film were studied. The microstructure, morphology, moisture absorbability, and thermal properties of the film were also evaluated. Results showed that the starch/lignin composite film, cast under optimized conditions, was homogeneous and soft. The tensile strength and elongation ratio of the composite film were higher than that of the corn starch film. At a temperature, higher than 320 degrees C, the weight loss rate of the starch/lignin film was lower than that of the starch film and its char residue at 750 degrees C was more than the corn starch film. This showed that the starch/lignin film had better thermal stability at higher temperatures. More importantly, the water absorption rate of starch/lignin film was 238 +/- 3%, which was 1.3 times than that of the corn starch film. The moisture content of the film was also higher than the corn starch sample. Hence, the prepared starch/lignin cross-linked film can be used as a biodegradable, water absorbent material for packaging and in agricultural mulching.