Rheological Behavior Of Nano-Cellulose Reinforced Polyurethane

MIRNA A. MOSIEWICKI; TARA RICHARSON; NORMA E. MARCOVICH; MIRTA I. ARANGUREN; MARIA L. AUAD

Rio de Janeiro, Brasil

Conferencia; International Conference on Science and Technology of Composite Materials”, COMAT 2007; 2007

Composite films were prepared by casting and solvent evaporation. It is known that the reinforcement of polymers using nanoparticles, even in a few percentages, can generate important changes in the viscoelastic properties of the melts or the concentrated solutions. In this work, the rheological behavior of molten polyurethanes films reinforced with cellulose nanowhiskers was studied. The measurements were carried out in the linear viscoelastic range using small strains. Important viscoelastic changes were observed close to the percolation concentration (liquid to solid transition), ~ 1 wt% of cellulose nanofibers. The samples with less than 0.5 wt% of cellulose exhibited Newtonian liquid behavior. However, the results show that the addition of more than 0.5 wt% of filler increases the low-frequency viscosity indicating the presence of a non-Newtonian behavior in the composite. This fact and the appearance of a plateau in the storage modulus at low frequencies indicate important interparticle interactions that can be associated with the percolation threshold. A simple percolation model was applied in order to model the obtained the results before and after the percolation concentration.