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

Abstract

The activation of the shape-memory effect of nanocomposites (NC) by alternating magnetic fields requires exceeding the switching temperature T s. Different factors, which are influencing this process, have been investigated exemplarily. 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 the surroundings, are influencing the accomplishable temperature in an alternating magnetic field. We used MNP having an iron(II,III)oxide core embedded in amorphous silica, which were homogeneously distributed in a polymer matrix by extrusion molding. 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(εcaprolactone)diol (PCL) and 2,2(4),4-trimethylhexanediisocyanate (TMDI) as junction unit. We could demonstrate that a nanoparticle content up to 10 wt-% do not decisively change the shape-memory properties or mechanical properties of PDC based materials.

Shape-memory properties of magnetically active triple-shape nanocomposites based on a grafted polymer network with two crystallizable switching segments

“…In addition H required for indirect heating to T mid = T max > T m,PEG = 40°C and T high = T max > T m,PCL = 70°C were determined for CLEG(040)C05 to H mid = 22.2 kA·m -1 and H high = 29.4 kA·m -1 . The inserted model calculation based on Equation (4) showed that T max correlated with H 2 as previously reported for other composite systems [38,40]. Here it becomes apparent, that for CLEG(040)C02 the obtained data and the theoretical prediction of the model calculation were in good agreement, while CLEG(040)C05 and CLEG(040)C10 showed a significant deviation in the H-range of 15 kA·m -1 to H = 22.4 kA·m -1 , which might be related to the higher particle loading.…”

“…For magnetic nanocomposites the specific absorption rate (SAR) or specific loss power is a key parameter, which is defined as the amount of heat released by a unit weight of the composite material per unit time [38,40]. It was further reported that SAR is proportional to the observed temperature difference "T = T max -'T env , which can be correlated to the square of the magnetic field strength (H 2 ) (Equation (4)), where k is a material related constant, which depends on several factors (e.g.…”

“…Narendra Kumar et al -eXPRESS Polymer Letters Vol.6, No.1 (2012) [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] …”

“…In the current study, we explored, whether the shape-memory properties of triple-shape nanocomposites achieved by thermal and indirectly by magnetical stimulation of SME could be adjusted by variation of the applied programming protocols. Magnetically-induced triple-shape nanocomposites, with different switching segment ratios and various nanoparticle contents (2.5, 5 and 10 wt%) were synthesized from crystallizable poly(!-caprolactone) diisocyanatoethyl methacrylate (PCLDIMA; M n = 8300 g!mol -1 , T m,PCL = 55°C), crystallizable poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMA; M n = 1000 g!mol -1 , T m,PEG = 38°C) and silica coated magnetite nanoparticles (SNP), named CLEGC, [39,40] according to a procedure previously described in ref. [41].…”

Review on the Functional Determinants and Durability of Shape Memory Polymers

“…For this purpose an alternating magnetic field is applied, causing strong particle motion inside the polymer matrix and thus local heating effects. Some recent advances and fundamental insights in this field were given by Lendlein's group [211,212]. Since magnetically induced actuation allows the triggering of the SM effect in a remote and wireless manner, the technique should be applicable to medical devices.…”