Filmes de nanocristais e nanofibrilas de celulose de eucalipto e abacaxi (curauá) por continous casting
Resumo
New materials from cellulose have been developed, such as cellulose
nanocrystals (CNC) and cellulose nanofibrils (CNF). Different morphologies of
the cellulose can lead to the formation of films with different thermal,
mechanical and optical properties in relation to conventional cellulose films. The
objective of this work was to evaluate the effect of different dimensional scales
of cellulose, micro and nanometric, on the production of cellulose films from two
vegetable species and their thermal, mechanical, morphological and optical
properties. Eucalyptus fibers and pineapple leave fiber (curauá) (PALF) were
used as cellulosic fibers for this study. The films of eucalyptus and pineapple
cellulosic fibers were prepared by filtration and casting, and the CNC and CNF
films were obtained by continuous casting. The CNC and CNF films showed
mechanical tensile strength in the order of 9 to 35 MPa higher than the films of
cellulose fibers, regardless of the origin of the fiber. The continuous casting
process produced CNC and CNF films that presented different mechanical
resistance in the longitudinal direction of the process with respect to the
transverse direction. This behavior may be related to how hydrogen bonds and
mechanical anchorages occur between nanofibers. The thermal stability of the
nanocellulose films was lower in the order of 20 to 150 ºC than in the films of
fibers due to the routes of obtaining the CNC and CNF. Nanofiber films
presented lower opacity in the order of 3 to 60% lower than the films of fibers
due to the diameter of the nanocelluloses. Curauá fibers had the highest
crystallinity index (Ic) reaching 87%. It is concluded that the properties studied
were influenced by the type of nanocellulose (CNC or CNF), the origin of the
cellulose (eucalyptus or pineapple), and the micro and nanometric scale of the
fibers.