Cyclic thermomechanical tests

Sauter, T., Heuchel, M., Kratz, K, and Lendlein, A. (2013) Quantifying the shape-memory effect of polymers by cyclic thermomechanical tests. Polym. 

Maximum deformation, parameter in cyclic, thermomechanical tests Free state deformation after cooling Volume fraction Critical volume fraction Volume resistivity Maximum stress 1,4-Butanediol Carbon black Carbon nanotube Dimethylformamide DMTA Dynamic mechanical analysis at varied temperatures DSC Differential scanning calorimetry / Frequency... 

High temperature, parameter in cyclic, thermomechanical tests Low temperature, parameter in cyclic, thermomechanical tests Melting temperature... 

Programming temperature, parameter in cyclic, thermomechanical tests... 

The SME of the network nanocomposite with 42 wt% POSS content was investigated. Here POSS crystallites were used to fix the temporary shape. The cyclic thermomechanical test started with heating the composite to 110°C. At this temperature, the sample was deformed by applying a load of 0.23 N and then cooled under this load to 30 C (POSS crystallization occurred according to DSC measurements... 

Fig. 15 Thermomechanical properties of SMPU/POSS nanocomposites, (a) Storage tensile modulus and tanS depending on temperature for SMPU with different POSS/polyol ratios (i) 0, (ii) 0.98, (iii) 1.67, and (iv) 2.63. (b) Cyclic thermomechanical tests for SMPU/POSS (POSS/polyol = 2.623). Three cycles are shown (solid line) first cycle, (broken line) second cycle, and (dotted line) third cycle. The asterisk marks the beginning of the cycle and the arrows denote the various stages, specifically (1) deformation, (2) cooling/fixing, (3) unloading, and (4) recovery. Reprinted with permission from [117], Copyright 2008, American Chemical Society...

Cyclic, Thermomechanical Testing of Triple-Shape Polymers. 130... 

Besides the variation of the thermomechanical test set-up (e.g., cyclic, thermomechanical tests or three-point flexural bending tests) and the application of different types of programming and recovery modules as described in Table 2, the resulting... 

Fig. 14 Results of a strain-controlled cyclic, thermomechanical test. Results of strain-controlled cyclic, thermomechanical test of amorphous polymer network LGF2 synthesized from (ohgo[(l-lactide)-ran-glycolide]dimethaycrylates (M = 2,800gmop and Tg = 53 °C) for different Tiow (a) Tiow = 10°C and (b) Flow = 50°C n cycle number, a stress elongation. Taken and modified from ref. [13], Copyright 2007. Reproduced by permission of The Royal Society of Chemistry (RSC). http //dx.doi.oig/10.1039/b702515g...

Characterisation of SMPs by techniques such as cyclic thermomechanical tests and differential scanning calorimetry (DSC) is typically conducted in the dry state. Although such standard dry conditions are highly relevant to compare SMP properties with data from the literature, the impact of a physiological environment should generally be considered for SMP for biomedical applications. 

Loading the same drugs by swelling into amorphous SMP networks derived from star-shaped oLG tetrole did not affect the materials shape-memory functionality as can be seen from congruent curves in cyclic thermomechanic tests (Eig. 8a). 

Cyclic thermomechanical testing of a polymer with an oligo[glycolide-co-(L-lactide)] as switching segment with T = 35°C hard... 

In order to verify some of the long term predictive capabilities of the finite element model described in the previous sections, the transverse creep of a IM7/5260 [90]i6 specimen subjected to cyclic thermomechanical loading investigated in an earlier study [8] was used as a benchmark. The authors of that study performed creep and recovery tests to characterize the non-linear creep behavior of the composite and then subjected the composite specimens to cyclic thermomechanical loading for up to 6 months. 

Cyclic, thermomechanical tensile tests were performed for the nanocomposites with POSS/polyol ratio = 2.63 (see Fig. 15b). The sample was firstly heated to 80°C (T > Tg) and deformed (1) by ramping to a load of 0.3N. The sample was cooled under this load (2) to 10°C, to fix the temporary, elongated shape. After unloading (3) the sample was heated (4) to 80°C to recover the permanent shape. The first cycle showed about 5% creep occurring between the elongation and fixing step over... 

The effect of magnetic nanoparticles on the cyclic, thermomechanical tensile tests of TFX nanocomposites is shown in Fig. 22. Here TE and a nanocomposite from TFX and 7.5 wt% magnetic particles were compared. In these tests, the samples were elongated at a temperature 71,igh, which was higher than Tsv, but lower than Tians of the hard domains. Strain was kept constant for a certain time interval to allow relaxation. The elongated samples were cooled to fix the temporary shape. This step was performed under stress-control, which resulted in an increase of strain as a consequence of entropy elasticity. The SME was initiated by reheating the composite to... 

Fig. 22 Results of cyclic, thermomechanical tensile tests under stress-free condition of TFX materials. Tiow = 0°C, Thigh = 80°C, and m = 50%. (a) TFX (b) composite from TFX and 7.5 wt% magnetic nanoparticles. Reprinted by permission from ref. [85]. Copyright 2006, National Academy of Sciences, U.S.A.

On the macroscopic level the extent to which a temporary deformation can be fixed and the recovery of the permanent shape or the recovery stress are the most important characteristics of the shape-memory effect (SME), which can be quantified in cyclic, thermomechanical tensile tests or bending tests. Such cycUc tests consist of a SMCP module that can be performed either under stress or strain control... 

Cyclic, Thermomechanical Tensile Tests of Dual-Shape Polymers. 118... 

Different test procedures have been described in the literature for quantification of an SME. One of the most powerful and widely used test procedures are cyclic, thermomechanical tensile tests. Quantification of the SME by cyclic, thermomechanical tensile tests follows tailored test procedures. These test procedures consist of a programming module, where the temporary shape is created, and a recovery module, where the permanent shape is recovered. The programming module can be performed under stress-controlled or strain-controlled conditions the recovery module can be carried out under stress-free conditions or under constant strain [4, 13]. The combination of certain programming and recovery modules results in different cycle types, which are presented in Table 2. Several thermomechanical... 

Triple-shape polymers can change on demand from a first shape (A) to a second shape (B) and from there to a third shape (C), when stimulated by two subsequent temperature increases [10, 26, 27]. Specific cyclic, thermomechanical tensile experiments were developed to characterize the triple-shape effect (Chapter Shape-Memory Polymers and Shape-Changing Polymers [101] and Sect. 2.2) quantitatively. Analogous to the experiments for dual-shape materials, each cycle of these tests consisted of a programming and a recovery module. A cycle started with creating the two temporary shapes (B and A) by a two-step uniaxial deformation, followed by the recovery module, where shape (B) and finally shape (C) were recovered. 

Fig. 17 Cyclic, thermomechanical tensile test for quantification of triple-shape effect - two step programming, (a) Strain and temperature as a function of time taken from the fifth cycle for MACL(45) multiphase network composed of crystallizable PCL segments and amorphous poly(cyclohexyl methacrylate) segments with 45 wt% PCL content (rtrans,A = Tm.PCL = 50°C and Ftrans.B = = Fg pcHMA = 140°C). The solid line indicates strain the dashed line indicates tem-...

Fig. 8 Effect of EN and EL loading, respectively, on stress-strain curves in strain-controUed cyclic thermomechanical experiments in air (a), shape-recovery curves upon heating in stress-controUed experiments (b), and stress-strain curves in tensile tests (c). Figures from [39], Copyright 2009, with permission from the Material Research Society...

Fig. 4. Schematic demonstration of the results of the cyclic thermomechanical investigations for two different test programs (a) e-a diagram Ci) stretching to at high cooling...

Thermomechanical property of Zr02 i FGM was investigated by the cyclic differential thermal load testing. 

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