Abstract
It remains a great challenge to fabricate bio-based soy protein isolate (SPI) composite film with both favorable water resistance and excellent mechanical performance. In this study, waterborne epoxy emulsions (WEU), which are low-cost epoxy crosslinkers, together with mussel-inspired dopamine-decorated silk fiber (PSF), were used to synergistically improve the water resistance and mechanical properties of SPI-based film. A stable crosslinking network was generated in SPI-based films via multiple physical and chemical combinations of WEU, PSF, and soy protein matrixes, and was confirmed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and solid state 13C nuclear magnetic resonance (13C NMR). As expected, remarkable improvement in both water resistance and Young’s modulus (up to 370%) was simultaneously achieved in SPI-based film. The fabricated SPI-based film also exhibited favorable thermostability. This study could provide a simple and environmentally friendly approach to fabricate high-performance SPI-based film composites in food packaging, food preservation, and additive carrier fields.
Highlights
Due to environment disturbances and the envisaged future shortfall of petroleum and petroleum-derived products, interest has been ignited for the development of environmentally friendly materials from renewable and biodegradable resources such as proteins, polysaccharides, and lipids [1,2,3,4]
The surface hydrophilicity of the soy protein isolate (SPI)-based films was investigated by water contact angles (WCA, OCA-20, Dataphysics Instruments GmbH, Beijing, China)
We found that the SPI/waterborne epoxy emulsions (WEU) film exhibited a relatively rougher fracture surface, which may be film spectra, the resonance strength related to the α-C in the SPI/PSF and SPI/PSF/WEU films became attributable to the crosslinking reaction between the epoxy groups of WEU and the soy protein side weaker, while the resonance strength related to the β-C in the SPI/PSF and SPI/PSF/WEU films chain
Summary
Due to environment disturbances and the envisaged future shortfall of petroleum and petroleum-derived products, interest has been ignited for the development of environmentally friendly materials from renewable and biodegradable resources such as proteins, polysaccharides, and lipids [1,2,3,4]. Previous reports have developed various strategies to solve these two problems via chemical grafting [5,10], physical blending [8], crosslinking [11,12,13], and enzymatic treatment [14,15], and chemical crosslinking has been proven to be the most efficient approach for the improvement of SPI-based film [16]. Epoxy group-containing crosslinkers have admirable effects on the mechanical properties and water resistance of SPI-based film [17]. This is due to the formation of a dense crosslinking network via multiple reactions between active epoxy groups and polar groups, such
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