Morphological Investigation of Nanocomposites from Sorbitol Plasticized Starch and Tunicin Whiskers

TLDR

Nanocomposites were fabricated by plasticizing waxy maize starch with sorbitol and incorporating tunicin whiskers, then conditioning the films at different relative humidities and characterizing them with SEM, DSC, water‑uptake, and WAXS. The composites exhibited a single glass‑rubber transition with no transcrystallization; the transition temperature increased up to ~10–15 wt % whisker loading before decreasing, and crystallinity rose with higher moisture or whisker content.

Abstract

Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a stable aqueous suspension of tunicin whiskers-an animal cellulose-as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using scanning electron microscopy, differential scanning calorimetry, water uptake experiments, and wide-angle X-ray scattering studies. Contrarily to our previous report concerning tunicin whisker filled glycerol plasticized starch nanocomposites (Macromolecules 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystallization of amylopectin on cellulose whisker surfaces and resultant antiplasticizing effects were observed. It was found that the glass-rubber transition temperature of the plasticized amylopectin matrix first increases up a whiskers content around 10-15 wt % and then decreases. A significant increase in crystallinity was observed in the composites by increasing either moisture content or whiskers content.