|Willett, Julious - J L|
Submitted to: Journal of Biobased Materials and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2007
Publication Date: 12/1/2007
Citation: Stevens, E.S., Willett, J.L., Shogren, R.L. 2007. Thermoplastic starch-kraft lignin-glycerol blends. Journal of Biobased Materials and Bioenergy. 1(3):351-359. Interpretive Summary: There is considerable current interest in developing plastics from renewable resources such as corn. Although corn starch can be processed into a plastic-like material, it has relatively low strength and flexibility and poor water resistance. It has been found that lignin, a cheap byproduct of wood pulping, can be blended with starch and glycerol giving stronger, stiffer materials. Lignin was dispersed into very small "nanosized" domains during extrusion processing, suggesting good adhesion with the starch. These results should be useful to scientists and engineers in academia, government and the plastics, packaging and paper industries who are interested in developing biodegradable plastics.
Technical Abstract: Starch-kraft lignin-glycerol blends were extruded in a twin-screw extruder to produce non-brittle films. One week after extrusion, films with a mid-range composition of 52% starch, 20% lignin, and 28% glycerol showed a tensile strength at break of 2.8 MPa, Young's modulus of 48 MPa, and elongation at break of 73%. After aging for eight months, the same films were stronger and stiffer, with corresponding values of 7.1 MPa, 281 MPa, and 24%, respectively. A small dependence of properties on added ammonium hydroxide was found. Lignin did not improve water resistance relative to starch controls; aged films showed an average water absorption of 50% by weight after a two-hour immersion. Factor analysis gave statistically significant predictive equations for mechanical properties and water absorption as a function of composition. The effect of glycerol on properties depends on lignin content.