Polymer, Vol.77, 361-365, 2015
Structural origin of stress and shape recovery in shape memory starch
As other kinds of polymer materials, amorphous starch obtained by extrusion exhibits shape memory properties when submitted to a specific type of thermomechanical treatment, called Shape Memory Creation Procedure (SMCP). Depending on the draw temperature used in SMCP, X-ray diffraction shows that the amorphous structure of starch is modified, with increasing anisotropy for low temperatures. Concurrently, the draw temperature affects both shape and stress recovery, with a correlation between the maximum stress recovered and the level of anisotropy induced. Besides, the maximum of stress recovery appeared systematically below or at the glass transition temperature, while shape recovery occurred mainly above the glass transition temperature. These results are discussed in terms of molecular scale and mobility. (C) 2015 Elsevier Ltd. All rights reserved.