Starch-Based Foams Nucleated and Reinforced by Polysaccharide-Based Crystals

Abstract

Environmentally friendly starch-based foams nucleated and reinforced by two kinds of polysaccharide-based crystals were successfully developed through two-step extrusions. The effects of varying additions of crystals on the properties of the starch-based foams were studied. We found that the crystals added resulted in the foams having more homogeneous cell structures and significantly improved their mechanical performances. The foam containing 5 wt % cellulose crystals had the lowest water absorption, highest resilience, and best compressive strength. We attribute this synergy to the nucleation and reinforcement interactions in the extrusion foaming enabled by adding cellulose crystals and starch crystals. Cellulose crystals have higher thermal stability and crystallinity than starch crystals. Hence, the cellulose crystals provide better processability, viscoelastic properties, and higher glass transition temperature for starch-based foams, generally improving foam properties. The apparent density (ρa) of starch-based foams was within the range of 19.94 to 32.53 kg/m3, which is equivalent to that of the commercial expanded polystyrene (EPS) and significantly lower than that of most other extruded starch-based foams. This technique has been used in biodegradable packaging, such as loose-filler, insulation, and shockproof boxes