Cellulose microcrystals (CMC) can be used as reinforcing material in the preparation of composite
films. This study aimed to evaluate the effect of CMC in starch and chitosan-based films
properties. Starch/CMC and Chitosan/CMC composite films were formulated with 1% (w/v) of
biopolymer, 0.25% (w/wbiopolymer) glycerol and 0.1% or 0.2% of CMC. The solutions were
prepared at 70◦C during 30 min under stirring and submitted to 45 min of ultrasonication.
Afterwards were dried in an air-circulating oven at 30◦C for 24 h. The effect of CMC incorporation
was evaluated in respect to the surface morphology on a scanning electron microscope (SEM).
Solubility was expressed as percentage of the film dry matter solubilized after 24 h immersion in
distilled water, and mechanical properties were measured using a texture analyzer following the
guidelines of ASTM D 882-10. X-ray diffraction analyses (XRD) were used to evaluate the
crystallinity of the samples. SEM micrographs of films with the incorporation of CMC revealed an
irregular structure with high heterogeneity and that the roughness of the surface of the films
increased for higher concentrations of CMC. Nevertheless, the surface of starch and chitosan
films in the absence of CMC are smooth. Regarding to XRD patterns, it was observed that the
addition of CMC leads to the presence of reflection peaks at 2θ=22.5° which are related to the
cellulose crystalline structure. The values of solubility in water for films with 0.1% and 0.2% of
MCM are statistically lower (p<0.05) than for chitosan and starch control films, thus indicating
that the presence of CMC reduces the solubility of the film in water. The incorporation of CMC in
films decreased the tensile strength values of starch-based films and the elongation at break
(p<0.05). Regarding chitosan-based films the incorporation of CMC showed to be effective in
increasing the tensile strength values, however leads to a decrease of elongation at break values.
Overall, results showed that the incorporation of CMC in chitosan and starch-based films can be
used to change the properties of the films and that according to the biopolymer used distinct
behaviors can be obtained
