Article

Journal of the American Oil Chemists' Society

, Volume 78, Issue 8, pp 867-872

First online:

Thermal and mechanical properties of plastics molded from urea-modified soy protein isolates

  • Xiaoqun MoAffiliated withDepatment of Grain Science and Industry, Kansas State University
  • , Xiuzhi SunAffiliated withDepatment of Grain Science and Industry, Kansas State University Email author 

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Abstract

Soy protein has been considered as a potential alternative of some petroleum polymers in the manufacture of plastics. The purpose of this investigation was to characterize the thermal and mechanical properties of plastics made from urea-modified soy protein. Soy protein isolate was separated from the defatted soy flour, modified with various urea concentrations, and compression-molded into plastics. Differential scanning calorimetry showed that the temperatures of denaturation and the enthalpies of denaturation of the modified soy protein decreased as urea concentrations increased above 1 M. At the same urea concentration, molded plastics made from the modified soy proteins showed a similar temperature of denaturation as the modified soy protein, but a lower enthalpy of denaturation. Tensile strength and Young's modulus of the molded plastics from the modified soy proteins increased as urea concentration increased and reached their maximum values at 8 M urea modification. Both storage modulus and glass transition temperature of the plastics from the modified soy proteins increased as urea concentration increased. The plastics made from the 2 M urea-modified soy proteins showed improvements in elongation, tough fracture behavior, and water resistance. The urea may function as a denaturant, a plasticizer, and a filler.

Key Words

Denaturation dynamic mechanical property mechanical properties protein modification soy protein thermal property