Use of kraft lignin as filler for starch films

• Published in: Polymer degradation and stability Vol. 59; no. 1; pp. 273 - 277
• Main Authors: Baumberger, S., Lapierre, C., Monties, B., Valle, G. Della
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 1998; Elsevier Science; Elsevier
• Subjects: Applied sciences; Chemical and Process Engineering; Engineering Sciences; Exact sciences and technology; Food engineering; Forms of application and semi-finished materials; Life Sciences; Polymer industry, paints, wood; Sheets and films; Technology of polymers; Lignin; Property composition relationship; Film; Moisture regain; Mechanical properties; Water solubility; Oside polymer; Tensile property; Experimental study; Wheat starch; Extrusion molding; Heterogeneous mixture
• DOI: 10.1016/S0141-3910(97)00193-6
• ISSN: 0141-3910

Films containing 0–30% of commercial kraft lignin mixed with wheat starch were obtained by extrusion followed by thermal moulding. The influence of lignin content on the film mechanical properties was evaluated by stress-strain tests run at two ambient relative humidity levels. At 58% relative humidity and up to 20% lignin, a very slight increase of elongation and stress at break was observed. At 71% relative humidity and up to 30% lignin, the film resistance to elongation significantly decreased, compared to the control starch film. Dissolution tests and water sorption isotherms showed that lignin actually reduces the overall water affinity of the films. These results are consistent with the hypothesis of a twophase material consisting of a hydrophilic starch matrix filled with hydrophobic lignin aggregates, as confirmed by microscopic observations. Casting experiments showed that the lower molecular weight fraction of kraft lignin may be responsible for a slight plastification of starch.