Biodegradable extruded starch blends

Abstract

ABSTRACT:We prepared biodegradable extruded starch blends by first mixing starch with additives and then processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, solubility, biodegradability, rheological properties, molecular weight, and glass-transition temperature of the extruded blends were studied. Glycerol and urea, to some extent, could both decrease the tensile strength and increase the percentage elongation at break because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. The extruded starch blends showed thermoplasticity, and their melts behaved as pseudoplastic liquids at a comparatively low shear rate. The biodegradability of the extruded starch was slightly higher than that of native starch. The molecular weight of starch displayed a decreasing tendency after extruding modification.

Extrusion-Cooking of Starch

“…monoglycerides or glycerol, as flexibility improvers (Schogren, 1993). Addition of glycerol is of influenced on the onset of gelatinization and results in an increase in the activation energy for the melting of the starch crystallites and results in higher glass transition temperatures and higher interactions forces between glycerol and starch polymers (Della Valle et al, 1995, van Soest & Knooren, 1997, van Soest et al, 1996b, You et al, 2003. During the extrusion process high shear stresses and high values of energy input take place and under these conditions the melting process may be enhanced (Della Valle et al, 1995).…”

Starch Protective Loose-Fill Foams

“…In turn, urea or boric acid addition improve the elongation at break but decreases the tensile strength (Fishman et al, 2000;You et al, 2003;Yu et al, 1998).…”

Melt Blending with Thermoplastic Starch

“…Utilization of plasticizers other than water helps to stabilize the properties of TPS. The main plasticizer used in TPS composition is glycerol (Forssell et al 1997;Mathew & Dufresne, 2002;Souza & Andrade, 2002;Ma & Yu, 2004a;Ma & Yu, 2004b;Parra et al, 2004;Rodriguez-Gonzalez et al, 2003a;Rodriguez-Gonzalez et al, 2003b;Rodriguez-Gonzalez et al, 2004;Mali et al, 2005;Chand et al, 2006;Ma et al, 2006;Teixeira et al, 2007;Talja et al, 2007;Talja et al, 2008;Tena-Salcido et al, 2008;Chaudhary, 2010;Mendez-Hernandez et al, 2011) but other alcohols (Da Roz et al, 2006), polyols (Mathew & Dufresne, 2002;Parra et al, 2004;Mali et al, 2005;Da Roz et al, 2006;Talja et al, 2007;Chaudhary, 2010), sugars (Da Roz et al, 2006;Teixeira et al, 2007;Talja, 2008) or nitrogen compounds such as ethanolamine (Ma et al, 2006), formamide (Ma & Yu, 2004a;Ma & Yu, 2004b), acetamide (Ma & Yu, 2004a) or urea (You et al, 2003;Ma et al, 2006) have also been successfully employed. TPS materials have been prepared using casting process (Mathew & Dufresne, 2002;Parra, et al, 2004;Mali et al, 2005;Chand et al, 2006;…”