Acetylated Distarch Phosphate/Chitosan Films Reinforced with Sodium Laurate-Modified Nano-TiO2 : Effects of Sodium Laurate Concentration

Abstract

Nano-titanium dioxide (TiO₂ ) was modified with the surfactant sodium laurate (SL) via ultrasonic microwave-assisted technology to improve the dispersion of TiO₂ in polymer matrices. As revealed by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy analyses, SL was well adsorbed onto the TiO₂ surface through chemical bonding, resulting in SL-modified TiO₂ (TiO₂ -SLx). The hydrophobicity and dispersibility of TiO₂ -SLx increased significantly compared to unmodified nano-TiO₂ . With an increase in the SL concentration from 5% to 15%, the agglomeration of TiO₂ -SLx particles decreased considerably, while the particles were more uniform. TiO₂ -SLx nanoparticles (3 wt%) were then incorporated into acetylated distarch phosphate/chitosan (ADPS/CS) blended matrices to reinforce the biopolymers. Relative to unmodified TiO₂ , TiO₂ -SLx exhibited a better dispersion capability. Furthermore, as the SL concentration increased, the tensile strength (TS) of the composite films increased, while the elongation at break (E), water vapor permeability (WVP), and solubility all decreased. The composite film containing TiO₂ -SL15 (TiO₂ modified with 15% SL; ADPS/CS-TiO₂ -SL15 film) displayed the highest TS (31.50 MPa), which was 33.70% higher than that of the pure ADPS/CS film, whereas the ADPS/CS-TiO₂ -SL25 film exhibited the lowest E. Further, the ADPS/CS-TiO₂ -SL15 film displayed the lowest WVP (0.90 × 10^-12 g·cm^-1 ·s^-1 ·Pa^-1 ) and solubility (22.91%), which decreased by 30.23% and 26.03% compared to that of the pure ADPS/CS film, respectively. Therefore, SL modification and the use of ultrasonic microwave-assisted technology are promising for the preparation of nanofillers for biopolymer reinforcement. PRACTICAL APPLICATION: Nano-titanium dioxide (TiO₂ ) nanoparticles were modified using the anionic surfactant sodium laurate via ultrasonic-microwave assisted technology, to improve the dispersion of the TiO₂ nanoparticles in polymer matrices. Modified TiO₂ nanoparticles were incorporated into acetylated di-starch phosphate/Chitosan blend films, causing the tensile strength of the composite film to increase and the water solubility and water vapor permeability of the composite film to decrease, making the films suitable for packaging applications.

Keywords: acetylated distarch phosphate; chitosan; nano-titanium dioxide; nanocomposite film; sodium laurate.