The moisture diffusion coefficients indicate that
the addition of cellulose nanofibers reduced the moisture
diffusion of thermoplastic starch (Table 2). The moisture
diffusion coefficient was greatest for the neat TPS, and it
was decreasing with the increasing amount of cellulose
nanofibers. Therefore, we can say that the addition of
cellulose nanofibers restricts the moisture diffusion in
thermoplastic starch. The reduction of moisture absorption
of two hydrophilic materials, starch and cellulose, can be
explained by several factors: (1) moisture penetration is
reduced by the good interfacial adhesion between cellulose
and starch [26,36]; (2) cellulose is less hygroscopic than
starch due to higher degree of crystallinity, which is why
the moisture absorption reduces with addition of CNF
[11,26], and (3) formation of fibrous network of cellulose
prevents the swelling of the starch matrix and thus reduces
the moisture penetration