Abstract
We present a new method for the determination of highly precise continuous relaxation spectra. The method is based on the use of piecewise cubic Hermite splines, which are fairly easy to tabulate by using their knots. The Hermite splines method allows a continuous description of the spectrum by a series of polynomial functions. The numerical instabilities of the spectrum calculation are minimized by limiting the slope of the spectrum to physically meaningful values. The reproducibility of the spectrum calculation is within an error margin of about ±10% in the physically relevant relaxation time range. This method is able to retrieve the spectrum based on data calculated from a benchmark with high accuracy and precision.
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Notes
Or of a retardation time and strength.
Such a low error means that the largest deviation between input and fitted data is in the range of 0.1% (in this case around ω = 10 − 5 s − 1) and that that deviation is rather the consequence of numerical limitations of double precision numbers than that of a mismatch between the real and the fitted spectrum. Double precision numbers are absolutely required to correctly calculate spectra; otherwise, a very strange result might occur as a consequence of numerical errors.
References
Baumgärtel M, Winter HH (1989) Determination of discrete relaxation and retardation time spectra from dynamic mechanical data. Rheol Acta 28:511–519
Baumgärtel M, Winter HH (1992) Interrelation between continuous and discrete relaxation time spectra. J Non-Newton Fluid Mech 44:15–36
Baumgärtel M, Schausberger A, Winter HH (1990) The relaxation of polymers with linear flexible chains of uniform length. Rheol Acta 29(5):400–408
Boltzmann L (1874) Sitzb Kgl Akad Wiss Wien 2(Abt 70):725
Brabec CJ, Schausberger A (1995) An improved algorithm for calculating relaxation-time spectra from material functions of polymers with monodisperse and bimodal molar-mass distributions. Rheol Acta 34(4):397–405
Davies AR, Anderssen RS (1997) Sampling localization in determining the relaxation spectrum. J Non-Newton Fluid Mech 73(1–2):163–179
Dealy J, Larson RG (2006) Structure and rheology of molten polymers—from structure to flow behavior and back again. Hanser, Munich
Elster C, Honerkamp J, Weese J (1992) Using regularization methods for the determination of relaxation and retardation spectra of polymeric liquids. Rheol Acta 31(2):161–174
Emri I, Tschoegl NW (1993) Generating line spectra from experimental responses. Part I: relaxation modulus and creep compliance. Rheol Acta 32(3):311–321
Emri I, Tschoegl NW (1994) Generating line spectra from experimental responses. 4. Application to experimental-data. Rheol Acta 33(1):60–70
Ferry JD (1980) Viscoelastic properties of polymers. Wiley, New York
Ferry JD, Williams ML (1952) Second approximation methods for determining the relaxation-time spectrum of a viscoelastic material. J Colloid Sci 7:347–353
Gabriel C, Münstedt H (1999) Creep recovery behavior of metallocene linear low-density polyethylenes. Rheol Acta 38(5):393–403
Gabriel C, Münstedt H (2002) Influence of long-chain branches in polyethylenes on linear viscoelastic flow properties in shear. Rheol Acta 41(3):232–244
Gabriel C, Kaschta J, Münstedt H (1998) Influence of molecular structure on rheological properties of polyethylenes I. Creep recovery measurements in shear. Rheol Acta 37(1):7–20
Hansen S (2007) Estimation of the relaxation spectrum from dynamic experiments using Bayesian analysis and a new regularization constraint. Rheol Acta 47:169–178. doi:10.1007/s00397-007-0225-4
Honerkamp J (1989) Ill-posed problems in rheology. Rheol Acta 28(5):363–371
Honerkamp J, Weese J (1989) Determination of the relaxation spectrum by a regularization method. Macromolecules 22(11):4372–4377
Honerkamp J, Weese J (1993) A nonlinear regularization method for the calculation of relaxation spectra. Rheol Acta 32(1):65–73
Kaschta J, Schwarzl FR (1994a) Calculation of discrete retardation spectra from creep data: 1. Method. Rheol Acta 33(6):517–529
Kaschta J, Schwarzl FR (1994b) Calculation of discrete retardation spectra from creep data: 2. Analysis of measured creep curves. Rheol Acta 33(6):530–541
Kaschta J, Stadler FJ (2008) Avoiding waviness in the calculation of relaxation spectra. Rheol Acta (accepted)
Laun HM, Wagner MH, Janeschitz-Kriegl H (1979) Model analysis of nonlinear viscoelastic behavior by use of a single integral constitutive equation: stresses and birefringence of a polystyrene melt in intermittent shear flows. Rheol Acta 18(5):615–622
Mandelkern L (1993) The crystalline state, 2nd edn. Chap. 4. Washington DC, ACS
Mead DW (1994) Numerical interconversion of linear viscoelastic material functions. J Rheol 38(6):1769–1795
Piel C, Stadler FJ, Kaschta J, Rulhoff S, Münstedt H, Kaminsky W (2006) Structure–property relationships of linear and long-chain branched metallocene high-density polyethylenes and SEC-MALLS. Macromol Chem Phys 207(1):26–38
Plazek DJ, Echeverria I (2000) Don’t cry for me Charlie Brown, or with compliance comes comprehension. J Rheol 44(4):831–841
Schwarzl FR (1993) Polymermechanik. Springer, Heidelberg
Schwarzl F, Staverman AJ (1952) Higher approximations of relaxation spectra. Physica (The Hague) 18:791–798
Stadler FJ, Bailly C (2008) Effect of incomplete datasets on the calculation of continuous relaxation spectra from dynamic-mechanical data (submitted)
Stadler FJ, Münstedt H (2008) Terminal viscous and elastic rheological characterization of ethene-/α-olefin copolymers. J Rheol 52(3):697–712. doi:610.1122/1121.2892039
Stadler FJ, Kaschta J, Münstedt H (2005) Dynamic-mechanical behavior of polyethylenes and ethene-/α-olefin-copolymers: part I: α ′-Relaxation. Polymer 46(23):10311–10320
Stadler FJ, Piel C, Kaminsky W, Münstedt H (2006a) Rheological characterization of long-chain branched polyethylenes and comparison with classical analytical methods. Macromol Symp 236(1):209–218
Stadler FJ, Piel C, Klimke K, Kaschta J, Parkinson M, Wilhelm M, Kaminsky W, Münstedt H (2006b) Influence of type and content of very long comonomers on long-chain branching of ethene-/α-olefin copolymers. Macromolecules 39(4):1474–1482
Stadler FJ, Gabriel C, Münstedt H (2007) Influence of short-chain branching of polyethylenes on the temperature dependence of rheological properties in shear. Macromol Chem Phys 208(22):2449–2454
Stadler FJ, Kaschta J, Münstedt H (2008) Thermorheological behavior of long-chain branched metallocene catalyzed polyethylenes. Macromolecules 41(4):1328–1333. doi:1310.1021/ma702367a
Tschoegl NW (1989) The phenomenological theory of linear viscoelastic behavior. Springer, Berlin
Tschoegl NW, Emri I (1992) Generating line spectra from experimental responses. III. Interconversion between relaxation and retardation behavior. Int J Polym Mater 18(1–2):117–127
Tschoegl NW, Emri I (1993) Generating line spectra from experimental responses. Part II: storage and loss functions. Rheol Acta 32(3):322–327
van Ruymbeke E, Orfanou K, Kapnistos M, Iatrou H, Pitsikalis M, Hadjichristidis N, Lohse DJ, Vlassopoulos D (2007) Entangled dendritic polymers and beyond: rheology of symmetric Cayley-tree polymers and macromolecular self-assemblies. Macromolecules 40(16):5941–5952
Winter HH, Mours M (2005) IRIS-handbook. IRIS Development, Amherst, USA
Acknowledgements
The authors want to acknowledge the financial support from Communauté Française de Belgique. FJS would like to thank Dr. J. Kaschta and Prof. em. Dr. F. R. Schwarzl (University Erlangen-Nürnberg) and Prof. Dr. H. H. Winter (University of Massachusetts, Amherst) for the stimulating discussions about this topic.
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Stadler, F.J., Bailly, C. A new method for the calculation of continuous relaxation spectra from dynamic-mechanical data. Rheol Acta 48, 33–49 (2009). https://doi.org/10.1007/s00397-008-0303-2
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DOI: https://doi.org/10.1007/s00397-008-0303-2