Nanoclay-tethered shape memory polyurethane nanocomposites

The study investigated shape memory properties of nanoclay-tethered polyurethane nanocomposites. Polyurethanes based on tone (PCL) diol, methylene diisocyanate, and butane diol and their nanocomposites of reactive nanoclay were prepared by bulk in an internal mixer and the values of shape fixity and shape recovery stress were determined as function of clay content. The melting point of crystalline soft segment was used as the transition temperature to actuate the shape memory actions. It was seen that clay particles well in the polymer, decreased the crystallinity of the soft segment phase, and promoted phase mixing between the hard and soft segment Nevertheless, the soft segment crystallinity was enough and in some cases increased due to stretching to exhibit excellent shape fixity and recovery ratio. A 20% increase in the magnitude of shape recovery stress was obtained with the addition of 1 wt% nanoclay. The room perature tensile properties were seen to depend on the competing influence of reduced soft segment crystallinity and the clay content. the tensile modulus measured at temperatures above the melting point of the soft segment crystals showed continued increases with clay (C) 2007 Elsevier Ltd. All rights reserved.