Kinetics and dynamics of two-way shape-memory behavior of crosslinked linear high-density and short-chain branched polyethylenes with regard to crystal orientation

Kinetic and dynamic aspects of the two-way shape-memory effect in covalent networks on the basis of linear high-density and two short-chain branched polyethylenes having appreciably different crystallinity and crystallization/melting temperatures are strongly affected by the crosslink density and applied uniaxial load. The crystallinity of the samples was found to play a key role in the shape-memory performance as it principally determined the capacity to develop the two-way shape-memory effect and the ability of the covalent network to perform mechanical work against the applied external force. Wide-angle X-ray scattering revealed preferred crystal c-axis orientation and its quasi-discrete change with evenly increasing load. The results of modeling the two-way shape-memory behavior of high-density polyethylene under different loads revealed excellent accordance with experimental findings. Theoretical analysis predicted the quasi-discrete change of the orientation of the crystal c-axis as a result of the change of crystal structure. (C) 2015 Elsevier Ltd. All rights reserved.