Preparation and characterization of starch films reinforced with citrate cellulose nanocrystals

Abstract

Citrate-modified bacterial cellulose nanocrystals (citrate CNCs) were prepared by a green one-pot dual acid (citric and hydrochloric acids) method and used them to reinforce three types of starch films; corn, wheat and rice starch films. The average length and width of citrate CNCs were 583 and 46 nm, respectively. The degree of citrate substitution on CNCs was 0.075 and its crystallinity index was closely to the original bacterial cellulose. The effect of various amount of citrate CNCs (0-20%wt of starch) on film property was study. Three starch films showed the same trend of examination results. The film thickness of most films was in a range of 0.20-0.24 mm and the increase of CNCs amount increase the film turbidity. The FE-SEM morphology revealed the good dispersion of citrate CNCs in the starch film matrix. The addition of citrate CNCs in all starches showed the continuing enhancement of crystallinity, Tdeg, and mechanical property. The tensile strength of starch/citrate CNCs films increased gradually while Young’s modulus increased dramatically. This indicated that the elasticity of films decreased if the amount of citrate CNCs increased. Among of three starches, citrate CNCs exhibited the highest influence on the mechanical property of wheat starch films.