Temperature induced shape memory behavior of Nanocellulose Composites

M. L. AUAD; M. A. MOSIEWICKI; V. CONTOS; S. NUTT; N.E. MARCOVICH; M. I. ARANGUEN

Madison, Estados Unidos

Conferencia; 9th International Conference of Wood &Biofiber Plastic Composites; 2007

Smart polymeric materials capable of “remembering” their original shape after having been deformed and later application of an external stimulus are called shape memory polymers (SMPs).  We are interested in segmented polyurethane (PU) based materials with shape memory behavior. The reinforcement of SMPs using nanofillers, is a new approach of enhancing the performance of these materials. The incorporation of these fillers into SMPs can produce performance enhancements (particularly elastic modulus) at small nanoparticle loadings (~1-2 wt %).  The addition of nanofillers allows to produce stiffer materials and yet with deformation capacity comparable to that of the unfilled polymer and enhanced recovery force. In this work, the use of cellulose nanocrystals was investigated. They were prepared by acidolysis of microcrystalline cellulose and dispersion in an organic solvent to be used as nanoreinforcement of segmented PU. The presence of the nanocrystals induce a more clear separation of soft and hard segments, as indicated by DSC and X ray measurements. Remarkably, the modulus of the films was significantly increased (~ 40%) by the addition of cellulose at concentrations as low as 0.5, 1wt %. Tensile testing of the films under cycled temperatures allowed investigating the shape memory response of these cellulose nanocomposites. The response was highly repeatable after the second cycle with shape recovery in the order of 80%.