Commercially available shape memory polymer (SMP) Estane (designation: ETE75DT3 NAT022) is investigated by means of dynamic mechanical thermal analysis (DMTA) technique in torsion mode using the Modular Compact Rheometer MCR-301 (Anton Paar GmbH). Amplitude sweep tests have been run below and above the glass transition temperature to establish the linear viscoelastic range (LVR) in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTA data. Temperature sweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduli and the storage and loss compliances as well as the viscosities. These tests have been carried out in heating mode with different rates and at different strain amplitudes. The short- and long-term behavior of SMP Estane have been studied by frequency sweep tests performed at different temperatures and data have been transformed into time-domain properties by applying time-temperature superposition principles. All these DMTA data provide the experimental basis for the study of relaxation processes, property-structure relationships, and the shape memory effect in this little-known SMP. 1. Introduction Thermoresponsive shape memory polymers (SMPs) have the ability to recover a permanent shape from a programmed temporary shape upon heating. The characterization and modeling of this phenomenon, known as the shape memory effect (SME), require comprehensive experimental studies of mechanical, thermal, and functional properties of this class of smart materials [1–12]. In particular, the temperature- and time-dependent behavior of thermoresponsive SMPs are one of the most important indicators of their functional properties such as shape fixity, shape recovery, and stress recovery [2, 6, 10, 12]. Moreover, the shape recovery property is directly related to the temperature and frequency (time) dependency of elastic and viscoelastic material parameters, which must be determined using reliable measuring methods for every particular SMP. The viscoelastic behavior of polymers including SMPs may be studied in several experimental methods like steady-state deformation, stress relaxation, creep, or oscillatory dynamic deformation. The results of tests are quantified using material functions such as steady viscosity, relaxation modulus, creep compliance, and storage and loss modulus. Additional tests are needed to study the coupling between viscoelastic and thermal properties of polymers. The standard quasi-static tensile tests together with creep and stress
References
[1]
A. Lendlein and S. Kelch, “Shape-memory polymers,” Angewandte Chemie—International Edition, vol. 41, no. 12, pp. 2035–2057, 2002.
[2]
C. Liu, H. Qin, and P. T. Mather, “Review of progress in shape-memory polymers,” Journal of Materials Chemistry, vol. 17, no. 16, pp. 1543–1558, 2007.
[3]
I. A. Rousseau, “Challenges of shape memory polymers: a review of the progress toward overcoming SMP's limitations,” Polymer Engineering and Science, vol. 48, no. 11, pp. 2075–2089, 2008.
[4]
J. Leng, H. Lu, Y. Liu, W. M. Huang, and S. Du, “Shape-memory polymers—a class of novel smart materials,” MRS Bulletin, vol. 34, no. 11, pp. 848–855, 2009.
[5]
P. T. Mather, X. Luo, and I. A. Rousseau, “Shape memory polymer research,” Annual Review of Materials Research, vol. 39, pp. 445–471, 2009.
[6]
W. Wagermaier, K. Kratz, M. Heuchel, and A. Lendlein, “Characterization methods for shape-memory polymers,” Advances in Polymer Science, vol. 226, no. 1, pp. 97–145, 2010.
[7]
M. Heuchel, J. Cui, K. Kratz, H. Kosmella, and A. Lendlein, “Relaxation based modeling of tunable shape recovery kinetics observed under isothermal conditions for amorphous shape-memory polymers,” Polymer, vol. 51, no. 26, pp. 6212–6218, 2010.
[8]
C. Schmidt, A. M. S. Chowdhury, K. Neuking, and G. Eggeler, “Stress-strain behavior of shape memory polymers by 1 WE method: application to tecoflex,” Journal of Macromolecular Science A, vol. 48, no. 3, pp. 204–210, 2011.
[9]
A. M. S. Chowdhury, C. Schmidt, K. Neuking, and G. Eggeler, “Comparative studies on thermomechanical behavior of veriflex, a shape memory polymer, for a low strain ( %): laser experiments,” Journal of Macromolecular Science A, vol. 48, no. 9, pp. 707–712, 2011.
[10]
M. Heuchel, T. Sauter, K. Kratz, and A. Lendlein, “Thermally induced shape-memory effects in polymers: quantification and related modeling approaches,” Journal of Polymer Science B, vol. 51, no. 8, pp. 621–637, 2013.
[11]
T. Sauter, M. Heuchel, K. Kratz, and A. Lendlein, “Quantifying the shape-memory effect of polymers by cyclic thermomechanical tests,” Polymer Reviews, vol. 53, no. 1, pp. 6–40, 2013.
[12]
T. D. Nguyen, “Modeling shape-memory behavior of polymers,” Polymer Reviews, vol. 53, no. 1, pp. 130–152, 2013.
[13]
N. W. Tschoegl, The Phenomenological Theory of Linear Viscoelastic Behavior, Springer, Berlin, Germany, 1989.
[14]
J. Ferry, Viscoelastic Properties of Polymers, John Wiley & Sons, New York, NY, USA, 3rd edition, 1980.
[15]
K. P. Menard, Dynamic Mechanical Analysis: A Practical Introduction, CRC Press, Washington, DC, USA, 1999.
[16]
R. Xiao, J. Choi, N. Lakhera, C. M. Yakacki, C. P. Frick, and T. D. Nguyen, “Modeling the glass transition of amorphous networks for shape-memory behavior,” Journal of Mechanics and Physics of Solids, vol. 61, no. 7, pp. 1612–1635, 2013.
[17]
S. Mogharebi, R. Kazakevi？iūt？-Makovska, H. Steeb, G. Eggeler, and K. Neuking, “On the cyclic material stability of shape memory polymer estane,” Materialwissenschaft und Werkstofftechnik, vol. 44, no. 6, pp. 521–526, 2013.
[18]
Anton Paar Germany GmbH, Physica MCR: The Modular Rheometer Series Anton Paar, 2006.
[19]
Anton Paar Germany GmbH, Rheoplus Software, Software Version: 3.0x, 2006.
[20]
J. Klesa, “Experimental evaluation of the properties of Veriflex shape memory polymer,” in Konference Studentské Tv？rci ？innosti (STC '09), 2009.
[21]
Z. Xia, H. J. Sue, A. J. Hsieh, and J. W. L. Huang, “Dynamic mechanical behavior of oriented semicrystalline polyethylene terephthalate,” Journal of Polymer Science B, vol. 39, no. 12, pp. 1394–1403, 2001.
[22]
R. Kazakevi？iūt？-Makovska, S. Mogharebi, H. Steeb, G. Eggeler, and K. Neuking, “A critical assessment of experimental methods for determining the dynamic mechanical characteristics of shape memory polymers,” Advanced Engineering Materials, vol. 15, no. 8, pp. 732–739, 2013.
[23]
J. Dealy and D. Plazek, “Time-temperature superposition—a users guide,” Rheology Bulletin, vol. 78, no. 2, pp. 16–31, 2009.
[24]
A. J. Levine and S. T. Milner, “Star polymers and the failure of time—temperature superposition,” Macromolecules, vol. 31, no. 24, pp. 8623–8637, 1998.
[25]
O. Starkova and A. Aniskevich, “Limits of linear viscoelastic behavior of polymers,” Mechanics of Time-Dependent Materials, vol. 11, no. 2, pp. 111–126, 2007.
[26]
N. A. Hardikar, S. Bobba, and R. Jha, “Applicability of time temperature superposition principle to an immiscible blend of polyphenyleneoxide and polyamide,” Journal of Polymer Engineering, vol. 31, no. 2-3, pp. 223–236, 2011.
[27]
Y. F. Shutilin, “Use of the Williams-Landel-Ferry and Arrhenius equations in describing the relaxational properties of polymers and polymer homologues,” Polymer Science U.S.S.R., vol. 33, no. 1, pp. 119–127, 1991.
[28]
C. M. Yakacki, S. Willis, C. Luders, and K. Gall, “Deformation limits in shape-memory polymers,” Advanced Engineering Materials, vol. 10, no. 1-2, pp. 112–119, 2008.
