Effect of Cellulose Nanofiber Addition to a Segmented Polyurethane with Shape Memory Properties

AUAD, MARÍA L.; RICHARDSON, TARA; MARCOVICH, NORMA E.; ARANGUREN, MIRTA

Siegen

Congreso; POLYCHAR18 - World Forum on Advanced Materials; 2010

The effect of the addition of cellulose nanofibers to a synthesized segmented polyurethane (SPU) presenting shape memory properties was investigated. Shape memory polymers are materials capable of storing a deformed shape and self-recovering their original one as a response to an external stimulus, which in the present study corresponds to the heating of the sample above a "switch" temperature. The polyurethane (PU) was synthesized in solution of dimethylformamide (DMF) using the usual technique of two step -synthesis, with toluene-diisocyanate (TDI), polytetramethylene-glycol (Mn=2900 g/mol) as the source of the soft segments domain and butanediol as chain extender. The cellulose nanofibers (CNF) were obtained by acid hydrolysis of microcrystalline cellulose (Avicel PH-101, FMC BioPolymer, U.S.A.) in concentrated sulfuric acid aqueous solution. 1 The nanocrystals obtained were washed, freeze dryed and redispersed in DMF. Previous studies carried out in our laboratories showed that incorporation of the CNF during the synthesis of the PU lead to covalent bonding between polymer and nanofibers with the consequent loss of the shape memory properties of the materials, an unwanted result. 2 Thus, the CNF were incorporated into the PU after completing the synthesis. Films of the neat PU and cellulose nanofibercomposites were prepared by solution/suspension casting. The resulting nanocomposites were rubbery elastic films that were tested to study their thermal, dynamicmechanical and mechanical behavior, as well as their shape memory response.