Fractal Structure of Microcrystalline Cellulose Obtained by Method of Spray Drying

In a fractal structure of beads of different sizes obtained by spray-drying of aqueous dispersions of microcrystalline cellulose (MCC) was studied. These beads are formed as a result of aggregation of rod-shaped cellulose nanocrystalline particles (CNP). It was found that increasing the average radius (R) of the formed MCC beads results in increased porosity (P) and reduced density ( ρ ). The dependences of P and ρ on scale factor (R/r) can be expressed by power-law equations: ( ) P E D o R P P r − = and ( ) D E R d r ρ ρ − = , where the fractal dimensions P D = 2.887 and P D =2.986 are close to Euclidean dimension E=3 for three-dimensional space; r=3nm is radius of cellulose nanocrystalline particles, P o = 0.03cm 3 /g is porosity and d=1.585g/cm 3 is true density (specific gravity) of CNP, respectively. Thus, with the increase in the size of formed MCC beads, the order in the packing of the beads is distorted conforming to theory of diffusion-limited aggregation process.