Abstract
In this study, we investigated the barrier properties of a montmorillonite-reinforced biomass material, starch. Organically modified montmorillonite materials were prepared from natural montmorillonite by reacting it with dodecyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride or octadecyl trimethyl ammonium chloride under ultrasonic conditions. The composite starch films incorporated with these organically modified montmorillonite samples were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and X-ray diffraction. The results showed that the introduction of montmorillonite decreases the transmittance of the composite film by 10% in the visible region and significantly inhibits UV-light transmittance. The decomposition temperature of the composite film ranges from 200 to 500 °C, with a weight loss rate of 80%. The distance between the montmorillonite layers increases from 0.14 nm in the non-magnetized state to 1.49 nm after magnetization. The oxygen permeability of the starch film modified by organic montmorillonite (0.067 cm3/m2·d) is lower than that of the montmorillonite starch film without magnetization (0.097cm3/m2·d). The oxygen barrier capacity is close to zero. Particularly in the ordered magnetic montmorillonite starch composite film, the oxygen barrier ability is the best. Therefore, modified montmorillonite could serve as an excellent reinforcing agent for cassava starch films and effectively improve the oxygen barrier performance of the films.
Highlights
The apparent morphology and size of the organic montmorillonite and magnetic organic montmorillonite were characterized by transmission electron microscopy (TEM; Hitachi HT7700, Hitachi Hitech Company) at an acceleration voltage of 80 kV
The microscopic morphology of the organic montmorillonite and organic montmorillonite/starch composite films were characterized by scanning electron microscopy (SEM; F16502, Phinom, The Netherlands) at the test voltage of 10 kV
These results indicate that the organic modifier was successfully intercalated between the montmorillonite interlayers and they increased the interlayer spacing of the montmorillonite, effectively elongating the effective paths for small molecule transport through the material [16]
Summary
Many researchers have studied montmorillonite as a reinforcement agent for composite films, the barrier properties of starch-based films with organically modified montmorillonite introduced via intercalation under ultrasonic conditions have not been studied. Starch-based films have been used in packaging They have not found wider use in other commercial and consumer goods, owing to their poor mechanical and barrier properties [10]. We prepared different organically modified montmorillonite samples (hereafter referred to as organic montmorillonite) by reacting montmorillonite with different organic modifiers (amines) at different dosages for different reaction times and used each of them as a reinforcing agent to improve the barrier properties of starch films. By magnetizing the organic montmorillonite using an iron chloride solution, we increased the distance between the montmorillonite layers and extended the passage of small gas molecules in the composite material to enhance the barrier mechanism of the composite film. The composite film can be used in the fields of packaging, agricultural moisture retention, everyday preservation and medicine and is of great significance
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