Investigation of parameters to achieve temperatures required to initiate the shape-memory effect of magnetic nanocomposites by inductive heating

The activation of the shape-memory effect of nanocomposites (NC) by alternating magnetic fields requires exceeding the switching temperature Ts. Different factors, which can influence this process, have been investigated. The intrinsic properties of magnetic nanoparticles (MNP), their content and distribution in the polymer matrix as well as the heat transport conditions, which are essentially determined by the surface to volume ratio (S/V) of the specimens and their surroundings, influence the achievable temperature in an alternating magnetic field. We used MNP having an iron (II, III) oxide core embedded in amorphous silica, which was homogeneously distributed in a polymer matrix by extrusion moulding. The thermoplastic polymer matrix consists either of an aliphatic polyetherurethane (TFX) for demonstration of the basic correlations between magnetic field and the sample, or of a biodegradable multiblock copolymer (PDC), which is prepared from hard segment forming poly(p-dioxanone)diol (PPDO), switching segment forming poly(e-caprolactone)diol (PCL) and 2,2(4),4-trimethylhexanediisocyanate (TMDI) as a junction unit. We could demonstrate that a nanoparticle content up to 10 wt% does not decisively change the shape-memory properties or mechanical properties of PDC-based materials.