Impact of the Amylose/Amylopectin Ratio of Starch-Based Foams on Foaming Behavior, Mechanical Properties, and Thermal Insulation Performance

Starch-based foams have attracted great attention as alternatives to expanded polystyrene because of their sustainability, biodegradability, and low thermal conductivity. Herein, we report high-thermal insulation starch blend foams with systematically controlled compositions of amylose and amylopectin. Starch blend foams are fabricated using two different types of starch (i.e., waxy corn starch and high-amylose corn starch) in various blending ratios (0:10, 2:8, 4:6, 6:4, 8:2, and 10:0). The samples with different compositions of amylose and amylopectin show differences in crystallinity and rheological properties that are responsible for the foaming behavior. The samples with higher amylose content show a lower degree of the breakup of crystalline regions during gelatinization and higher viscosity, and well-expanded foaming behavior is inhibited in these samples. The samples with high amylose ratios provide irregular cell structures, high foam density, high flexural strength, low water absorption, and poor thermal insulation performance. Conversely, the samples with high amylopectin ratios provide relatively regular cell structures, low foam density, poor flexural strength, high water absorption, and excellent thermal insulation performance. Notably, the optimized sample, M26P74, which has 26% amylose and 74% amylopectin, shows equivalent levels of thermal insulation performance and flexural strength as conventional thermal insulating materials. This result suggests potential applications of starch-based foams as thermal insulating materials used in cold chains through an eco-friendly and sustainable approach.