Starch nanocrystal permeability coefficient

The barrier properties of starch nanocrystals/natural rubber nanocomposites were also investigated [39]. For these systems, the water vapour transmission rate, the diffusion coefficient of oxygen, the permeability coefficient of oxygen and its solubility, were measured. It was observed that the permeabiUty to water vapour, as well as to oxygen, decreased when starch nanocrystals wctc added These effects were ascribed to the platelet-like morphology of the nanocrystals. 

Starch nanocrystals also reduced the oxygen diffusion through the nanocomposite films as shown from the decrease of diffusion coefficient values upon filler content increase in Table 14.3. It is believed that the platelet-like low permeable structures of the starch stand in the way of the oxygen molecules (O2 diameter 3.47 A), increasing the tortuosity of the diffusion path. The... 

Table 14.3 Water vapour transmission rate (WVTR), diffusion coefficient (D), permeability coefficient (P) and solubility (S) of oxygen for starch nanocrystal/NR nanocomposite films.

Slavutsky et al. (2014) prepared starch/cellulose nanocrystals (CNCs) films and their water barrier properties were studied. The measured film solubility, contact angle, and water sorption isotherm indicated that reinforced starch/CNC films have a lower affinity to water molecules than starch films. Permeability, dififusivity, and solubility coefficients indicated that the permeation process was controlled by the water diffusion and was dependent on the tortuous pathway formed by CNC incorporation. The decrease in surface hydrophilicity and the improvement in water vapor barrier properties with the addition of CNC showed that these nanocomposites present excellent potential as a new biomaterial for application in food packaging and conservation. 

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