Carbon nanoparticles/soy protein isolate bio-films with excellent mechanical and water barrier properties

Different sized carbon nanoparticles (CNPs) were synthesized from glucose through a one-step hydrothermal process and soy protein isolate (SPI) films modified by the CNPs were prepared. Morphology and size distributions of the prepared CNPs were characterized by transmission electron microscopy. The effects of different sized CNPs (CNPA, CNPB, and CNPC) on mechanical properties of films were evaluated. Furthermore, the effects of different contents of CNPC with the smallest size on properties of films were analyzed including structure, morphology, moisture content, total soluble matter, water vapor permeability (WVP), mechanical properties, and thermal stability. The attenuated total reflectance-Fourier transform infrared results demonstrated that there were carboxyl and hydroxyl groups on the surface of CNPs. In addition, the CNPs led to a phase change of SPI matrix as shown in X-ray diffraction results. The tensile strength and modulus of SPI/CNPC films with 5.0g CNPC increased by 82.97% and 79.74% compared to the unmodified one, respectively. In addition, SPI/CNPC films with 5.0 g CNPC exhibited the best water barrier property, which was a 48.36% decrease in WVP compared to SPI film. (C) 2015 Elsevier B.V. All rights reserved.