Shape memory segmented polyurethanes: dependence of behavior on nanocellulose addition and testing conditions

The response of synthesized shape memory segmented polyurethanes (PUs) was affected by the addition of cellulose nanocrystals, as well as by the various conditions selected to carry out thermomechanical cyclic tests. The PUs were synthesized from an alpha-hydro-omega-hydroxy-poly(ethylene oxide), tolylene-2,4-diisocyanate and 1,4-butanediol as chain extender. Nanocomposites were prepared by mixing a suspension of cellulose nanocrystals in N,N-dimethylformamide with the thermoplastic PU dissolved in the same organic solvent. The thermal properties of the neat PU and resulting composites were examined using differential scanning calorimetry. It was found that cellulose addition increases the PU soft segment melting and crystallization temperatures and the degree of crystallinity of this phase. Shape memory behavior was studied using cyclic thermal tensile tests. Both neat PU and composites exhibit shape memory properties, with fixity and recovery values that depend on heating temperature, imposed deformation, deformation rate and nanofiller addition. (C) 2011 Society of Chemical Industry