Moisture absorption
The effect of cellulose nanofibers on the kinetics of water
absorption of the specimens was studied according to the
ASTM D 5229 standard by exposing the samples to 98% relative
humidity and determining the water uptake as a function
of time until the moisture equilibrium content was
reached. Specimens were cut from the compression molded
films, and the specimen size was 15 15 0.3 mm. The
film thickness 2 L was therefore considered thin enough
for the molecular diffusion to be one-dimensional. Before
absorption experiments, specimens were dried overnight
in an oven at 100 C and then weighed. The average weight
of the dried specimen was 72 mg (instead of the recommended
5.0 g in the standard due to lack of space). The
oven-dry samples were placed in a desiccator with a 98%
RH. At specific time intervals the samples were removed