Physical and mechanical properties of soy protein-based plastic foams

Flexible plastic foams using soy protein isolate (SPI), soy protein concent rate (SPC), and defatted soy flour (DFS) were produced by interacting prote ins with glycerol-propylene oxide polyether triol (polyol), surfactant, tri ethanolamine (cross-linking agents), tertiary amine (catalyst), and water ( blowing agent). The density, compressive stress, resilience, and dimensiona l stability of foams with SPI, SPC, and DFS increased as the initial concen tration of soy protein increased. The foam density increased with increasin g weight percentage of SPI, SPC, and DFS. The resilience values of SPI cont aining foam increased with the increasing addition of SPI up to a maximum 3 0% SPI addition. An increase in SPI up to 20% caused an increase in the com pressive stress (225 kPa) in comparison to control polyurethane foam (187 k Pa). The control foam and foam containing 20% DFS had a similar load-deform ation relationship. The foam containing 20% SPI and SPC also exhibited a si milar shape, but with a higher compressive stress. The compressive stress o f all foams was steeply increased after 55% strain, since the foams complet ely collapsed upon compression.