A multifunctional carbon nanotube reinforced nanocomposite modified via soy protein isolate: A study on dispersion, electrical and mechanical properties

Excellent multifunctional polymeric nanocomposite cannot be achieved without good dispersion and well protection of nanofillers, for which a highly efficient, cost-effective and environmental benign nanofiller treatment approach is demanded. Herein, we report that soy protein isolate (SPI), an extracted protein from soybean, is applied as a highly performed bio-surfactant to treat carbon nanotubes (CNTs), resulting in nanocomposite with tremendously improved dispersion, electrical and mechanical properties. TEM, UV-vis and dynamic light scattering (DLS) and real-time optical microscopic characterizations show that, compared with a conventional surfactant, sodium dodecylsulfate (SDS), SPI more effectively and efficiently functionalize CNTs with less agglomerates and more stable particle size distribution. The electrical conductivity of the SPI-CNTs/epoxy increased by 6 orders of magnitude at 0.5 wt% vs pure epoxy, which is 4 orders higher than the pristine CNTs/epoxy and even 1 order higher than that of the SDS treated counterpart. The tensile modulus, strength and fracture toughness of the SPI-CNTs/epoxy increased by 27%, 24% and 32% at 1.0 wt% loading of CNTs, respectively, which is 20%, 26% and 18% higher than the pristine CNTs/epoxy and 10%, 23% and 21% higher than the SDS-CNTs/epoxy. The in-situ tensile test accompanied by digital image correlation technique (DIC) shows that cracks are effectively arrested by the SPI-CNTs while SDS-CNTs cannot. These results establish a solid foundation for the application of SPI in the polymeric nanocomposite fields. (C) 2020 Elsevier Ltd. All rights reserved.