Preparation And Characterization Of Carbon-Dots Modified Soy Protein Isolate Film

Petroleum-based plastics are presenting more and more concerns since they are non renewable and non biodegradable. To solve these problems, soy protein isolate (SPI) has attracted more attention. However, SPI-based films possess some weaknesses involving brittleness and poor water resistance. So the modification of SPI is of great importance.In this study, SPI was used as raw materials. Firstly, orthogonal test was designed to obatin the optimal preparation parameters (SPI%, glycerol%, pH of film-forming solution, temperature of film-forming). Secondly, microwave was used to treat SPI and we also tried using microwave technology to synthesis C-dots from SPI. Finally, the modification effect of C-dots prepared from glucose was explored. The attenuated total reflectance-Fourier transform infrared, X-ray diffraction and scanning electron microscope were employed to investigate the structural changes of SPI films. Additionally, mechanical properties, water barrier properties and thermal property of SPI films were measured. The results were as follows:(1) Among the preparation parameters of SPI films, the glycerol concentration and pH of film-forming solution had bigger effect on mechanical properties and the glycerol concentration had the significant influence on tensile strength. With the comprehensive assessment of the morphology and properties of SPI films, the optimal preparation parameters of SPI films were obtained:the concentration of SPI and glycerol were 5% and 30%, separately, and the pH and temperature of film-forming solution were 9 and 45℃.(2) Based on the technic and method, we failed to synthesis C-dots from SPI. Microwave treatment made the structure of SPI unfolded and exposed more functional groups, which were hided in SPI before. The films treated by microwave at the power of 400 W showed the highest TS and E, which increased by 111.8% and 454.9%, respectively, compared to the SPI film. With the microwave power increasing to 400 W, the final contact angle grew to the biggest, giving SPI film higher surface hydrophobicity.(3) When the addition of CNPCwas 5.0 g, films exhibited a more coarse and tough cross-sections. The TS and E of SPI films modified with 5.0 g CNPC increased by 82.97% and 79.74% compared to the unmodified one, respectively. Besides, films modified with 5.0 g CNPC exhibited the best water barrier property, which was a 26.87% decrease in total soluble matter and a 48.36% decrease in water vapor permeability compared to SPI film. The addition of CNPC did not have much influence on the thermal property of SPI films.