| Abstract: | Thermal and rheological properties of sodium dodecyl sulfate (SDS)-modified soy protein isolate (SPI) adhesives were studied using differential scanning calorimetry (DSC) and rheometry. The ordered structure of native SPI was denatured as SDS concentration increased, and thermal stability of native SPI decreased at high SDS concentration. The enthalpy of SPI denaturation decreased significantly with increasing SDS concentration. Apparent viscosity of the SPI adhesives increased as SDS concentration increased. The SPI adhesives modified by high concentrations of SDS exhibited characteristics of a Newtonian-type flow. The SDS-modified SPI adhesives were applied to fiberboard, and effects of SDS concentration, press conditions, and assembly time on bond strength were investigated. Shear strength of the SPI adhesives increased with SDS concentration, reaching its maximum value at 3 wt% of SDS, and then decreased significantly. The shear strength increased as press time and/or press temperature increased. High press temperature (100 °C) and long press time (5 min) are needed to achieve relatively good adhesion properties. The shear strength also increased as assembly time increased. The shear strength of the SDS-modified SPI adhesives decreased after soaking in water for 24 h. |
