Physical and chemical reinforcement of chitosan film using nanocrystalline cellulose and tannic acid

Abstract

Chitosan film with nanocrystalline cellulose (NCC) as a physical reinforcement and tannic acid as a chemical crosslinker was prepared by the casting evaporation method. The objective was to improve its mechanical properties, reduce its moisture content and solubility, and maintain its biodegradability. This was done to examine its potential suitability as an ultra-lightweight wing membrane for a future biomimetic micro air vehicle. Different contents of nanofiller material and tannic acid were added to a chitosan matrix and comparisons were made with neat chitosan film. Mechanical test shows that the addition of NCC into the chitosan matrix improves the tensile strength by 69.8 % compared to neat chitosan. Insertion of tannic acid to the nanocomposite film further improves the tensile strength by 82.6 %. These reinforcement materials also reduce the moisture content up to 73.5 % and water solubility to 67.9 %. Morphological studies were carried out using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and an ultraviolet–visible spectrophotometer. The TEM images revealed the presence of nano-sized cellulose particles with high aspect ratios (average of 20.9). SEM images were examined to reveal the dispersion level of NCC and the effects of tannic acid in the film. Fourier-transform-infrared spectroscopy imagery was used to define the interaction of the molecules. X-ray diffraction analysis confirms that the addition of NCC increases the presence of crystalline structures in the film, which makes it more rigid. The addition of tannic acid changed the structure into an anhydrous crystalline conformation, when compared to neat chitosan film.