Research Article Characterization of Shape Memory Polymer ...downloads.hindawi.com/archive/2014/250258.pdf · of the paper. Finally, the experimental and analytical (theo-retical)

Research ArticleCharacterization of Shape Memory Polymer Estane byMeans of Dynamic Mechanical Thermal Analysis Technique

Rasa KazakeviIi0t-Makovska Aycan Oumlzlem Oumlzarmut and Holger Steeb

Mechanics-ContinuumMechanics Ruhr University Bochum Universitatsstraszlige 150 44780 Bochum Germany

Correspondence should be addressed to Rasa Kazakeviciute-Makovska rasakazakeviciute-makovskarubde

Received 27 September 2013 Accepted 1 December 2013 Published 9 January 2014

Academic Editor Chris Bowen

Copyright copy 2014 Rasa Kazakeviciute-Makovska et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Commercially available shape memory polymer (SMP) Estane (designation ETE75DT3 NAT022) is investigated by means ofdynamic 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 linearviscoelastic range (LVR) in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTAdata Temperaturesweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduliand the storage and loss compliances as well as the viscositiesThese tests have been carried out in heatingmode with different ratesand at different strain amplitudes The short- and long-term behavior of SMP Estane have been studied by frequency sweep testsperformed at different temperatures and data have been transformed into time-domain properties by applying time-temperaturesuperposition 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 theability to recover a permanent shape from a programmedtemporary shape upon heating The characterization andmodeling of this phenomenon known as the shape memoryeffect (SME) require comprehensive experimental studies ofmechanical thermal and functional properties of this classof smart materials [1ndash12] In particular the temperature-and time-dependent behavior of thermoresponsive SMPs areone of the most important indicators of their functionalproperties such as shape fixity shape recovery and stressrecovery [2 6 10 12] Moreover the shape recovery propertyis directly related to the temperature and frequency (time)dependency of elastic and viscoelastic material parameterswhichmust be determined using reliable measuringmethodsfor every particular SMP

The viscoelastic behavior of polymers including SMPsmay be studied in several experimental methods like steady-state deformation stress relaxation creep or oscillatory

dynamic deformationThe results of tests are quantified usingmaterial functions such as steady viscosity relaxation mod-ulus creep compliance and storage and loss modulusAdditional tests are needed to study the coupling betweenviscoelastic and thermal properties of polymersThe standardquasi-static tensile tests together with creep and stress relax-ation tests are often carried out at different ambient temper-atures to determine the temperature-dependent mechanicalresponse of the particular polymer under monotonic andsteady-state loading [13 14] Such tests although straightfor-ward and reliable are costly in both materials and time andoften limited to selected temperatures short-term responsesand low strain rates

Dynamic mechanical thermal analysis (DMTA) is avery efficient alternative technique for the study of time-frequency- and temperature-dependent mechanical prop-erties of polymeric materials [14 15] and may be usedto characterize various polymers including thermoplasticsthermosets elastomers and polymer blends as well as SMPsThis technique provides also information about relaxation

Hindawi Publishing CorporationSmart Materials ResearchVolume 2014 Article ID 250258 9 pageshttpdxdoiorg1011552014250258

2 Smart Materials Research

processes in polymers specifically the glass transition andsubglass processes [14ndash16] This makes DMTA particularlyuseful for the characterization of SMPs and it becomesan indispensable experimental method in study of thesesmart materials Additional advantages of using DMTA tocharacterize the thermoviscoelastic behavior of SMPs includeautomated testing precise control of the test environmentsimple preparation of test specimens and possibility ofperforming tests in a wide range of temperatures

In this work we present results of an extensive DMTAstudy of the commercially available thermoplastic polyure-thane (TPU) based SMP Estane (purchased from LubrizolOevel Westerlo Belgium) performed in torsion deformationmode using the Modular Compact Rheometer MCR-301equipped with temperature chamber The DMTA investiga-tions include the following specific experiments

(i) strain amplitude sweep tests at different temperaturesto determine the linear viscoelastic range (LVR) forthe tested polymer

(ii) temperature sweep tests at different frequencies withthe aim to study the coupling between temperatureand time-dependent properties and to evaluate relax-ation processes

(iii) temperature sweep tests in heating mode with differ-ent rates to evaluate the influence of this parameter onviscoelastic properties

(iv) temperature sweep tests on samples cut out fromplates in two perpendicular directions to identify apossible anisotropy in material structure or process-ing of the tested polymer

(v) frequency sweep tests at different isothermal temper-atures to determine the short- and long-time responseof this SMP

These special tests serve to characterize various aspectsand relative contributions of viscous and elastic responsesof the Estane In particular the frequency of oscillationdefines the timescale of tests and it follows that by observingpolymer response as a function of frequency the materialcan be probed at different timescales These measurementsare important in SMPs characterization because the overallresponse of thesematerials is due to contribution from severalmechanisms at the molecular and microscopic levels Thesemechanisms can be identified by observingmaterial responseat different frequencies

Conventional DMTA equipments such as the one usedin this study provide data for a tested SMP in a limitedtemperature and frequency range However when combinedwith theoretical concepts generally known as superpositionprinciples and related concepts of the so-calledmaster curvesthese datamay be used to determine the viscoelastic behaviorof the same material over a wider frequency (or time) rangeThe application of these theoretical concepts to SMP Estaneand the representative results are presented in the second partof the paper Finally the experimental and analytical (theo-retical) results for the tested polymer obtained in this studyare shortly discussed in reference to other thermoresponsiveSMPs extensively investigated in the literature

The SMP Estane has not yet drawn much attention on itsthermoviscoelastic properties The only known study is [17]where the material stability the functional fatigue and somethermal properties of this SMP have been investigated TheDMTAresults presented in this work provide complementarydata for this new smart polymer

2 Experimental

21 Material The thermoplastic polyurethane-based shapememory polymer Estane (designation ETE75DT3 NAT022)was purchased from Lubrizol (Oevel Westerlo Belgium) inthe form of plates of dimensions 80 times 90 times 2mm3 The plateswere cut into rectangle shape specimens with dimensions of10 times 50 times 2mm3 (Figure 1)

The same SMP has been previously studied in [17] usingspecimens that were injection-molded from granulates alsopurchased from Lubrizol

22 Experimental Setup and Test Procedures Dynamic me-chanical thermal analysis (DMTA) tests in torsion deforma-tion mode were performed in the temperature range fromminus5∘C to 150∘C using theModular Compact RheometerMCR-301 (Anton Paar GmbH) [18] equipped with standard fixtures(SRF12) for rectangular bars and a temperature chamber(CDT-180) having high temperature stability (plusmn03∘C) Theequipment and details of a fixed specimen are shown inFigure 2

In DMTA torsion mode tests a small axial force (aroundminus05N) is applied to the sample in order to maintain it undernet tension On this state of sample the harmonic twistangle (rotation) with prescribed amplitude and frequency issuperimposed and the resulting harmonic torque as well asthe phase lag or loss angle 120575 (in rad) is measured From theseraw data and sample dimensions the RheoPlus Software [19]computes the corresponding shear stress 120591 and shear strain120574 which in turn are used to determine the dynamic shearmodulus |119866lowast| the shear storage and loss moduli 1198661015840 and 11986610158401015840respectively and the loss factor 120582 These material parametersare related by the following formulae [14 15]

1003816100381610038161003816119866lowast1003816100381610038161003816 =radic11986610158402 + 119866101584010158402 119866

1015840=1003816100381610038161003816119866lowast1003816100381610038161003816 cos 120575

11986610158401015840=1003816100381610038161003816119866lowast1003816100381610038161003816 sin 120575 120582 = tan 120575 =

11986610158401015840

1198661015840

(1)

The complex modulus 119866lowast = 1198661015840 + 11989411986610158401015840 1198942 = minus1 determinedin the strain-controlled DMA tests describes the relaxationof the mechanical stress for a given strain In the stress-controlled DMA experiment a stress is given and theresulting strain is measured In this case the complex shearcompliance 119869lowast is determined directly from the applied stressand measured strain Equivalently it may be computed fromthe shear moduli measured in strain-controlled tests usingthe following theoretical formulae [14 15]

1003816100381610038161003816119869lowast1003816100381610038161003816 =1

|119866lowast| 119869

1015840=1198661015840

|119866lowast|2 119869

10158401015840=11986610158401015840

|119866lowast|2 (2)

Smart Materials Research 3

80 m

m10 mm

50 m

m

90 mm

Figure 1 Rectangular specimens cut out of the SMP Estane plate

(a)

(b)

Figure 2 Modular Compact Rheometer MCR-301 equipped withtemperature chamber (a) and details of specimen clamping (b)

where 1198691015840 and 11986910158401015840 are the storage and loss compliance respec-tively The complex compliance 119869lowast obtained in the stress-controlled DMA tests which is simply the inverse or recip-rocal of the complex shear modulus describes the strainretardation and the retardation time is a measure of the timedelay in strain after imposition of the stress

Besides the shear modulus and the shear compliancethere is another quantity called the viscosity to characterizethe rheological behavior of polymericmaterialsThe complexviscosity is defined as the ratio of the stress and strain rate andmay be computed from the complex shear modulus 119866lowast andthe frequency 120596 [14 15]

1003816100381610038161003816120578lowast1003816100381610038161003816 =

1003816100381610038161003816119866lowast1003816100381610038161003816

120596 120578

1015840=11986610158401015840

120596 120578

10158401015840=1198661015840

120596 (3)

where 1205781015840 and 12057810158401015840 are the dynamic and out-of-phase viscositiesrespectively The physical significance of all these dynamicquantities measured in DMTA may be better appreciatedin terms of energy stored and dissipated during harmonicdeformation [14 15]

3 Results and Data Analysis

The rheometer used in this study can perform a widerange of DMTA experiments including temperature rampfrequency and amplitude sweep tests in both stress- andstrain-controlled modes From such tests the determinedshear moduli and the loss factor are obtained as functions oftest parameters in the specified range

31 Strain Amplitude Sweep Data In order to use DMTAtechnique to accurately determine thermorheological prop-erties and to develop morphological relationships of materi-als a tested polymer must be deformed at amplitudes thatremain within the linear viscoelastic region (LVR) WithinLVR the viscoelastic response of the polymer is independentof the magnitude of deformation As a general rule thisregion must be determined for every type of polymer byDMTA amplitude sweep tests in which a frequency is fixedand the strain amplitude is incrementally increased

From the plot of the storage and loss moduli against thestrain amplitude for the SMP Estane shown in Figure 3 thelinear viscoelastic region is read off for three temperaturesthe room temperature and temperatures well-below andwell-above the glass transition temperature It is seen that for theshear strain amplitude up to 2 the shear moduli remainnearly constant and this determines the LVR for the EstaneThe strain sweep test is the first step in dynamic mechanicalanalysis and is always performed prior to a frequency sweeptest in order to determine an appropriate strain level fortemperature and frequency sweeps

32 Temperature Sweep Data The temperature-sweep testinvolves measurements of the storage and loss moduli andthe loss factor over a specified temperature range at constantstrain (or stress) amplitude and constant frequency Temper-ature sweeps can be carried out in ramp or stepwise fashion

Figures 4ndash6 show DMTA data obtained in the temper-ature ramp tests which were performed under the strain-controlled mode at seven frequencies (indicated in thefigures) with the shear strain amplitude of 001 and theheating rate 1 Kmin

In Figure 4(a) the storage shear modulus 1198661015840 and theloss shear modulus 11986610158401015840 are plotted against the temperaturefrom minus5∘ to 150∘C It is seen that the storage modulus1198661015840 decreases gradually with increasing temperature until

attaining the region of the glass transition Starting fromthat region changes in 1198661015840 with temperature are remarkablydifferent for low and high frequencies For the frequencieshigher than 2Hz a more rapid reduction in values of thestoragemodulus occurs However for the frequencies smallerthan 2Hz nonmonotonic variations of 1198661015840 with temperatureare observed The loss modulus 11986610158401015840 at all test frequencies


Storage modulus G998400


Strain amplitude 1205740 ()00 10 20 30 40

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100

Loss modulus G998400998400


T = minus6∘CT = 23∘CT = 100∘C

T = minus6∘CT = 23∘CT = 100∘C

Figure 3 Amplitude sweep test at different temperatures variationof the storage and loss shear moduli with strain amplitude

shows a nonmonotonic variation with temperature and thisdistinguishes the Estane from other investigated SMPs [8 920]

Typically the DMA temperature sweep tests of a polymersample scanned at different frequencies show that at higherfrequencies the storage modulus demonstrates higher val-ues and the glass transition temperature shifts to a highertemperature Figure 4(b) shows variations in the loss factor(damping coefficient) with temperature for all tested fre-quencies The temperature at which this coefficient reachesits maximum value is interpreted as the glass transitiontemperature of material [14 15] It is seen in Figure 4(b)that both the maximum value of the loss factor and theglass transition temperature increase with the increase of testfrequency

DMTA measurements over a range of temperaturesprovide valuable insight into the structure the morphologyand the viscoelastic behavior of SMPs In particular thesemeasurements are an important part of the technique forestablishing relaxation transitions For example during tem-perature sweep the temperature at crossover modulus 1198661015840 =11986610158401015840 is considered to signify the beginning of gel forming

(or gel melting) temperature During polymer melting thetemperature at crossover modulus is an indication of theldquosoftening pointrdquo of the polymer the onset temperature ofrapid melt and flow The temperature sweep test is alsohelpful to detect changes that would occur at rather high andpossibly inaccessible frequencies ifmeasurementsweremadeat room temperature

A further characterization of the tested SMP is obtainedby plotting the storage and loss compliances as well as thedynamic and out-of-phase viscosities as functions of temper-ature for different frequencies (Figures 5 and 6) All thesematerial parameters show the nonmonotonic behavior It is

Frequency



Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

(a)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

101

100

10minus1

10minus2

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Loss

fact

or ta

n 120575

(b)

Figure 4 Temperature scan at different frequencies variation ofthe storage and loss shear moduli (a) and loss factor (b) withtemperature

also seen that the viscosities display a stronger dependencyon frequency than the moduli and the compliances

33 Heating Rate Effects Figure 7(a) shows a plot of thestorage and loss moduli as functions of temperature fordifferent heating rates at constant testing frequency (1Hz)and constant strain amplitude (001) The purpose of such


Storage compliance J998400

Loss compliance J998400998400

Stor

age

loss

com

plia

nceJ

998400 J998400998400

(1M

Pa)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

10minus1

10minus2

10minus3

10minus4

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Figure 5 Temperature scan at different frequencies variation of thestorage and loss compliances with temperature

Interrupted line out-of-phase viscosity 120578998400998400

103

102

101

100

10minus1

10minus2

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

Solid lines dynamic viscosity 120578998400

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Visc

osity

120578998400 120578

998400998400(M

Pamiddots)

Figure 6 Temperature scan at different frequencies variation of thedynamic and out-of-phase viscosities with temperature

tests is to examine effects of heating rate on the transitionbehavior and other processes in polymeric material It is seenthat within experimental error the transition behavior doesnot appreciably alter with change in heating rate in the testedrange

The loss factor results are shown in Figure 7(b)The peaksare in this case very well resolved and the temperatures ofmaxima are easily detected A small shift towards higher



Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100

Heating rate120573 = 05∘Cmin120573 = 10∘Cmin120573 = 20∘Cmin

(a)

Temperature T (∘C)0 20 40 60 80 120100 140

Heating rate

100

10minus1

10minus2

120573 = 05∘Cmin120573 = 10∘Cmin120573 = 20∘Cmin

Loss

fact

or ta

n 120575

(b)

Figure 7 Temperature scan at different heating rates variation ofthe storage and loss shear moduli (a) and the loss factor (b) withtemperature

temperatures is observed for the tan 120575 peak with increasingheating rate A similar behavior of polymeric materials isusually seen in other thermal analysis techniques in heatingmode such as DSC

34 Processing Anisotropy Effects Only limited research hasfocused on possible nonisotropic effects in polymeric mate-rials Such effects could be due to material anisotropy pro-cessing anisotropy or deformation Each type of anisotropygreatly complicates the interpretation of DMTA data The


analysis of the structural anisotropy in oriented semicrys-talline polymers presented in [21] is a good example

Both the material and processing-induced anisotropy inpolymers may be detected by DMTA technique In [22]SMP Tecoflex has been studied by temperature sweep testsperformed on samples cut out in different directions from theinjection-molded plates but no anisotropic effect has beenobserved Similar DMTA tests have also been carried out onthe polymer Estane and the representative results are shownin Figure 8 The tested polymer has been purchased fromLubrizol in the form of plates (Figure 1) but the processingdetails are unknown Nevertheless it is seen (Figure 8) thatthe temperature sweep on the samples cut out from the platein two perpendicular directions shows nearly identical valuesof the storage and loss moduli This proves that this polymeris isotropic in respect to its material structure as well asprocessing

4 Long-Term Behavior

41 Frequency Sweep Data The frequency sweep is probablythe most efficient DMTA test in characterizing the viscoelas-tic behavior of polymeric materials including SMPs Sucha test performed in torsion mode at fixed strain amplitudeand temperature provides the storage and loss shear modulias well as the loss factor as functions of frequency Thecorresponding shear compliance and viscosity of a materialmay then be computed using formulae (2) and (3)

A typical dynamic mechanical analyzer such as that usedin this study can provide data only over a limited rangeof frequency or time and this is inadequate to track thelong-term viscoelastic behavior of a tested material Thetime-temperature superposition principle not only offers theopportunity to obtain the long-term behavior of polymericmaterials from the standard DMTA tests but also providesdata that are difficult to measure directly [14 15] Thisprinciple is based on the empirical assumption that theviscoelastic behavior of a polymer at one temperature isrelated to the viscoelastic behavior at other temperatures bya shift in frequency or time scale only [23] In other wordsthe frequency (or time) and the temperature in viscoelasticdata are equivalent and data at one temperature can besuperimposed upon data taken at different temperaturemerely by shifting the curves This has been shown to be truefor numerous polymeric materials [14 15 23ndash25]

42 Superposition Principles and Master Curves In order toverify the applicability of the time-temperature (equivalentlythe frequency-temperature) superposition principle for thetested polymer Estane the frequency sweeps were conductedat different isothermal temperatures ranging from 10∘C to75∘C and stepping every 5∘C for each sweep step In allthese tests the same range of frequencies from 001 to 15Hzat oscillation amplitude of 001 strain has been kept Thedata plotted as log-log curves are shown in Figure 9 In thisanalysis the lower frequency rangewas applied due to a bettercoincidence of the measured moduli and loss factor than athigher frequencies (Figure 4)

Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100



Axial directionTransverse direction

(a)

Axi

al d

irect

ion

Transverse direction

(b)

Figure 8 Variation of the storage and loss moduli with temperature(a) measured on samples cut out from the Estane plate in twoorthogonal directions (b)

From these data the master curve has been constructedby shifting some of these curves along the logarithmicfrequency axis to the left (to lower frequencies) and othersto the right (to higher frequencies) relative to the referencecurve at the temperature119879

0= 50∘CThis temperature is close

to the glass transition temperature of Estane (119879119892= 54∘C)The

shift factor data were obtained manually from the generationof the storage modulus versus frequency master curve on thelog-log scale (see Figure 10) The same shift factor was usedto generate the loss modulus versus frequency master curveshown in the same figure

The materials for which the time-temperature or equiv-alent principle applies are referred to as thermorheologicallysimplematerials and this may be verified in a number of waysdepending on the material parameter used for the study [1415] In the literature [23] the complexmodulus has been usedto assess the thermorheological simplicity of testedmaterialsFor the Estane the plot of themaster curves (Figure 10) showsthat the data at a higher temperature do not superimpose




Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1

Angular frequency 120596 (rads)

Temperature =10∘C30∘C40∘C45∘C50∘C55∘C60∘C65∘C75∘C

Figure 9 Plot of the storage and loss moduli versus frequency (log-log) for different temperatures

10minus4 100 104 108

Angular frequency aT120596 (rads)

10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101



Figure 10 The storage and loss moduli versus frequency mastercurves

very well that is the tested polymer is not in the class ofthermorheologically simple materials

43 Determination of Shift Factor Constants In terms ofthe dynamic moduli the time-temperature superpositionprinciple underlying the construction of master curves reads[14 15 23 26]

1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)

Here 119879 is the temperature 1198790denotes the reference temper-

ature and 119886119879is the horizontal shift factor In general the shift

factor represents the characteristics of relaxation processes ofa particular polymeric material

Dozens of formulas have been proposed in the literatureto link the shift factor of master curve to the chosen refer-ence temperature The most recognized empirical formula is

minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T

Temperature T (∘C)

ExperimentalWLFArrhenius

Figure 11 Experimental shifted data points versus temperature andcomparison with WLF and Arrhenius models

known as theWilliams-Landel-Ferry (WLF) equation [14 2327]

log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862

2are empirical constants (depending on the

reference temperature) to be determined by fitting the testdata of shift factor with this equation For the data shown inFigure 10 the values of these constants have been obtained1198621= 52 and 119862

2= 149

The secondwidely considered theoretical equation for theshift factor is known as the Arrhenius model [14 23 27]

log 119886119879=119864

119877(1

119879minus1

1198790

) (6)

Here 119877 denotes the ideal gas constant (119877 = 8314 JmoLK)and 119864 (measured in JmoL) is the activation energy

A comparison with experimental values of the shift factorshows that the WLF equation fits data reasonably well exceptat the lowest and highest temperature values (Figure 11) Asit may be seen in the same figure the Arrhenius model alsofails to represent data in the entire temperature range Theseobservations support the earlier conclusion that the SMPEstane may be considered as the thermorheologically simplematerial only in limited range of frequencies

A smooth master curve for the storage or loss modulus ofthe tested polymer may be constructed within the more gen-eral concept of thermorheologically complex (TRC)materials[23 26] However this concept involves the necessity ofintroducing the vertical shift factor besides the horizontal oneand this remains a contested issue in the literature [26]


5 Conclusions

This work is complementary to the parallel study by Mo-gharebi et al [17] and represents a step forward in thecharacterization of a little known SMP Estane It is worthpointing out the following results

(i) The linear viscoelastic range (LVR) determined byamplitude sweep tests run at different temperaturesproves that this polymer exhibits the linear behaviorin both glassy and rubbery phase in a far widerrange than it is usually suggested for the DMTAmeasurements

(ii) The temperature dependency of the storage and lossmoduli determined from temperature sweep testsshows the characteristic behavior typical for thermo-plastics

(iii) The commonly usedWilliams-Landel-Ferry equationand Arrhenius model to describe the temperature-and time-dependent behavior of polymers are notstrictly applicable for the SMP Estane

(iv) The master curves built up by means of a procedurebased on the time-temperature superposition princi-ple show that the tested polymer may be consideredas rheological simple only in limited time range

The primary aim of the related work [17] was to inves-tigate the functional properties of the same type of SMPthrough the standard shape memory thermomechanicalcycles and thermal properties using DSC and DMTA tech-nique Some properties of the Estane measured in this paperand in [17] agree fairly well at least qualitatively For examplethe glass transition temperature determined in [17] by DSCand DMTA methods (around 328K) coincides with thevalues that may be read off from the pick of the loss factordata presented in Figure 4 (around 54∘C = 327K) Howeverthe data presented in [17] are not directly comparable with thedata presented in this paper for two reasons

(1) in [17] the tested SMP (designation ldquoEstane ETE75DT3NAT022rdquo) was obtained fromLubrizol Corpo-ration as a granulate and samples have been producedby the injection molding process while in our studythe same SMPwas received from Lubrizol in the formof plates with unknown processing (Figure 1)

(2) DMTA data presented here and in [17] were obtainedusing different testing rigs (MCR-301 from AntonPaar and Eplexor 500N from Gabo resp) and differ-ent deformation modes (torsion deformation givingthe shear moduli 1198661015840 and 11986610158401015840 and three-point bendingdeformation giving the tension moduli 1198641015840 and 11986410158401015840resp) As discussed in [22] the ldquoexactrdquo comparisonof the shear moduli with the tension moduli requiresthe dynamic Poisson ratio Unfortunately none of theused test rigs measures the Poisson ratio Howevereven a very rough comparison based on the grossassumption that 1198641015840 = 31198661015840 gives a reasonable goodcoincidence of the two data

When comparing the experimental results obtained inthis work for the Estane with partial data published in theliterature for other types of SMPs the following aspects maybe noted

(i) The shift in tan 120575 peak to a higher temperature withthe increase of frequency of the scan for the Estane(Figure 7(b)) is smaller than that obtained by Klesa[20] for the Veriflex and the Tecoflex given in [22]This implies that the glass transition temperatureincreases with the increase of frequency for all theseSMPs (as expected) but to a lesser degree for theEstane

(ii) The storage and loss moduli as well as the loss factorof the Estane measured at isochronal conditions (119891 =1Hz) for the heating rates 120573 = 05 1 and 2∘Cminshow only small variations in the tested temperaturerange minus5ndash150∘C (Figure 7) It then follows that theglass transition behavior does not appreciably alterwith a change in heating rate in the tested rangeA similar influence of the heating rates was alsoobserved for the SMP tested by Yakacki et al [28]

Itmay be briefly stated that the results of thiswork providethe experimental basis for the study of structure-propertyrelationships and shape memory properties of the Estane

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] A Lendlein and S Kelch ldquoShape-memory polymersrdquo Ange-wandte ChemiemdashInternational Edition vol 41 no 12 pp 2035ndash2057 2002

[2] C Liu H Qin and P T Mather ldquoReview of progress in shape-memory polymersrdquo Journal of Materials Chemistry vol 17 no16 pp 1543ndash1558 2007

[3] I A Rousseau ldquoChallenges of shape memory polymers areview of the progress toward overcoming SMPrsquos limitationsrdquoPolymer Engineering and Science vol 48 no 11 pp 2075ndash20892008

[4] J Leng H Lu Y LiuWM Huang and S Du ldquoShape-memorypolymersmdasha class of novel smart materialsrdquo MRS Bulletin vol34 no 11 pp 848ndash855 2009

[5] P T Mather X Luo and I A Rousseau ldquoShape memorypolymer researchrdquoAnnual Review ofMaterials Research vol 39pp 445ndash471 2009

[6] W Wagermaier K Kratz M Heuchel and A Lendlein ldquoChar-acterizationmethods for shape-memory polymersrdquoAdvances inPolymer Science vol 226 no 1 pp 97ndash145 2010

[7] M Heuchel J Cui K Kratz H Kosmella and A LendleinldquoRelaxation based modeling of tunable shape recovery kineticsobserved under isothermal conditions for amorphous shape-memory polymersrdquo Polymer vol 51 no 26 pp 6212ndash6218 2010

[8] C Schmidt A M S Chowdhury K Neuking and G EggelerldquoStress-strain behavior of shape memory polymers by 1 WEmethod application to tecoflexrdquo Journal of MacromolecularScience A vol 48 no 3 pp 204ndash210 2011


[9] A M S Chowdhury C Schmidt K Neuking and G EggelerldquoComparative studies on thermomechanical behavior of veri-flex a shapememory polymer for a low strain (120576m = 70) laserexperimentsrdquo Journal of Macromolecular Science A vol 48 no9 pp 707ndash712 2011

[10] M Heuchel T Sauter K Kratz and A Lendlein ldquoThermallyinduced shape-memory effects in polymers quantification andrelated modeling approachesrdquo Journal of Polymer Science B vol51 no 8 pp 621ndash637 2013

[11] T Sauter M Heuchel K Kratz and A Lendlein ldquoQuantifyingthe shape-memory effect of polymers by cyclic thermomechan-ical testsrdquo Polymer Reviews vol 53 no 1 pp 6ndash40 2013

[12] T D Nguyen ldquoModeling shape-memory behavior of polymersrdquoPolymer Reviews vol 53 no 1 pp 130ndash152 2013

[13] N W Tschoegl The Phenomenological Theory of Linear Vis-coelastic Behavior Springer Berlin Germany 1989

[14] J Ferry Viscoelastic Properties of Polymers John Wiley amp SonsNew York NY USA 3rd edition 1980

[15] K P Menard Dynamic Mechanical Analysis A Practical Intro-duction CRC Press Washington DC USA 1999

[16] R Xiao J Choi N Lakhera CM Yakacki C P Frick and T DNguyen ldquoModeling the glass transition of amorphous networksfor shape-memory behaviorrdquo Journal of Mechanics and Physicsof Solids vol 61 no 7 pp 1612ndash1635 2013

[17] SMogharebi R Kazakeviciute-Makovska H Steeb G Eggelerand K Neuking ldquoOn the cyclic material stability of shapemem-ory polymer estanerdquoMaterialwissenschaft undWerkstofftechnikvol 44 no 6 pp 521ndash526 2013

[18] Anton Paar Germany GmbH Physica MCR The ModularRheometer Series Anton Paar 2006

[19] Anton Paar Germany GmbH Rheoplus Software SoftwareVersion 30x 2006

[20] J Klesa ldquoExperimental evaluation of the properties of Veri-flex shape memory polymerrdquo in Konference Studentske TvurciCinnosti (STC rsquo09) 2009

[21] Z Xia H J Sue A J Hsieh and J W L Huang ldquoDynamicmechanical behavior of oriented semicrystalline polyethyleneterephthalaterdquo Journal of Polymer Science B vol 39 no 12 pp1394ndash1403 2001

[22] R Kazakeviciute-Makovska SMogharebi H Steeb G EggelerandKNeuking ldquoA critical assessment of experimentalmethodsfor determining the dynamic mechanical characteristics ofshape memory polymersrdquo Advanced Engineering Materials vol15 no 8 pp 732ndash739 2013

[23] J Dealy and D Plazek ldquoTime-temperature superpositionmdashausers guiderdquo Rheology Bulletin vol 78 no 2 pp 16ndash31 2009

[24] A J Levine and S T Milner ldquoStar polymers and the failure oftimemdashtemperature superpositionrdquoMacromolecules vol 31 no24 pp 8623ndash8637 1998

[25] O Starkova and A Aniskevich ldquoLimits of linear viscoelasticbehavior of polymersrdquoMechanics of Time-Dependent Materialsvol 11 no 2 pp 111ndash126 2007

[26] N A Hardikar S Bobba and R Jha ldquoApplicability of timetemperature superposition principle to an immiscible blendof polyphenyleneoxide and polyamiderdquo Journal of PolymerEngineering vol 31 no 2-3 pp 223ndash236 2011

[27] Y F Shutilin ldquoUse of theWilliams-Landel-Ferry and Arrheniusequations in describing the relaxational properties of polymersand polymer homologuesrdquo Polymer Science USSR vol 33 no1 pp 119ndash127 1991

[28] C M Yakacki S Willis C Luders and K Gall ldquoDeforma-tion limits in shape-memory polymersrdquo Advanced EngineeringMaterials vol 10 no 1-2 pp 112ndash119 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


processes in polymers specifically the glass transition andsubglass processes [14ndash16] This makes DMTA particularlyuseful for the characterization of SMPs and it becomesan indispensable experimental method in study of thesesmart materials Additional advantages of using DMTA tocharacterize the thermoviscoelastic behavior of SMPs includeautomated testing precise control of the test environmentsimple preparation of test specimens and possibility ofperforming tests in a wide range of temperatures

In this work we present results of an extensive DMTAstudy of the commercially available thermoplastic polyure-thane (TPU) based SMP Estane (purchased from LubrizolOevel Westerlo Belgium) performed in torsion deformationmode using the Modular Compact Rheometer MCR-301equipped with temperature chamber The DMTA investiga-tions include the following specific experiments

(i) strain amplitude sweep tests at different temperaturesto determine the linear viscoelastic range (LVR) forthe tested polymer

(ii) temperature sweep tests at different frequencies withthe aim to study the coupling between temperatureand time-dependent properties and to evaluate relax-ation processes

(iii) temperature sweep tests in heating mode with differ-ent rates to evaluate the influence of this parameter onviscoelastic properties

(iv) temperature sweep tests on samples cut out fromplates in two perpendicular directions to identify apossible anisotropy in material structure or process-ing of the tested polymer

(v) frequency sweep tests at different isothermal temper-atures to determine the short- and long-time responseof this SMP

These special tests serve to characterize various aspectsand relative contributions of viscous and elastic responsesof the Estane In particular the frequency of oscillationdefines the timescale of tests and it follows that by observingpolymer response as a function of frequency the materialcan be probed at different timescales These measurementsare important in SMPs characterization because the overallresponse of thesematerials is due to contribution from severalmechanisms at the molecular and microscopic levels Thesemechanisms can be identified by observingmaterial responseat different frequencies

Conventional DMTA equipments such as the one usedin this study provide data for a tested SMP in a limitedtemperature and frequency range However when combinedwith theoretical concepts generally known as superpositionprinciples and related concepts of the so-calledmaster curvesthese datamay be used to determine the viscoelastic behaviorof the same material over a wider frequency (or time) rangeThe application of these theoretical concepts to SMP Estaneand the representative results are presented in the second partof the paper Finally the experimental and analytical (theo-retical) results for the tested polymer obtained in this studyare shortly discussed in reference to other thermoresponsiveSMPs extensively investigated in the literature

The SMP Estane has not yet drawn much attention on itsthermoviscoelastic properties The only known study is [17]where the material stability the functional fatigue and somethermal properties of this SMP have been investigated TheDMTAresults presented in this work provide complementarydata for this new smart polymer

2 Experimental

21 Material The thermoplastic polyurethane-based shapememory polymer Estane (designation ETE75DT3 NAT022)was purchased from Lubrizol (Oevel Westerlo Belgium) inthe form of plates of dimensions 80 times 90 times 2mm3 The plateswere cut into rectangle shape specimens with dimensions of10 times 50 times 2mm3 (Figure 1)

The same SMP has been previously studied in [17] usingspecimens that were injection-molded from granulates alsopurchased from Lubrizol

22 Experimental Setup and Test Procedures Dynamic me-chanical thermal analysis (DMTA) tests in torsion deforma-tion mode were performed in the temperature range fromminus5∘C to 150∘C using theModular Compact RheometerMCR-301 (Anton Paar GmbH) [18] equipped with standard fixtures(SRF12) for rectangular bars and a temperature chamber(CDT-180) having high temperature stability (plusmn03∘C) Theequipment and details of a fixed specimen are shown inFigure 2

In DMTA torsion mode tests a small axial force (aroundminus05N) is applied to the sample in order to maintain it undernet tension On this state of sample the harmonic twistangle (rotation) with prescribed amplitude and frequency issuperimposed and the resulting harmonic torque as well asthe phase lag or loss angle 120575 (in rad) is measured From theseraw data and sample dimensions the RheoPlus Software [19]computes the corresponding shear stress 120591 and shear strain120574 which in turn are used to determine the dynamic shearmodulus |119866lowast| the shear storage and loss moduli 1198661015840 and 11986610158401015840respectively and the loss factor 120582 These material parametersare related by the following formulae [14 15]

1003816100381610038161003816119866lowast1003816100381610038161003816 =radic11986610158402 + 119866101584010158402 119866

1015840=1003816100381610038161003816119866lowast1003816100381610038161003816 cos 120575

11986610158401015840=1003816100381610038161003816119866lowast1003816100381610038161003816 sin 120575 120582 = tan 120575 =

11986610158401015840

1198661015840

(1)

The complex modulus 119866lowast = 1198661015840 + 11989411986610158401015840 1198942 = minus1 determinedin the strain-controlled DMA tests describes the relaxationof the mechanical stress for a given strain In the stress-controlled DMA experiment a stress is given and theresulting strain is measured In this case the complex shearcompliance 119869lowast is determined directly from the applied stressand measured strain Equivalently it may be computed fromthe shear moduli measured in strain-controlled tests usingthe following theoretical formulae [14 15]

1003816100381610038161003816119869lowast1003816100381610038161003816 =1

|119866lowast| 119869

1015840=1198661015840

|119866lowast|2 119869

10158401015840=11986610158401015840

|119866lowast|2 (2)


80 m

m10 mm

50 m

m

90 mm


(a)

(b)




1003816100381610038161003816120578lowast1003816100381610038161003816 =

1003816100381610038161003816119866lowast1003816100381610038161003816

120596 120578

1015840=11986610158401015840

120596 120578

10158401015840=1198661015840

120596 (3)














Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100



T = minus6∘CT = 23∘CT = 100∘C

T = minus6∘CT = 23∘CT = 100∘C







Frequency



Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

(a)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

101

100

10minus1

10minus2

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Loss

fact

or ta

n 120575

(b)







Stor

age

loss

com

plia

nceJ

998400 J998400998400

(1M

Pa)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

10minus1

10minus2

10minus3

10minus4

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz



103

102

101

100

10minus1

10minus2

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140


f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Visc

osity

120578998400 120578

998400998400(M

Pamiddots)






Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100


(a)

Temperature T (∘C)0 20 40 60 80 120100 140

Heating rate

100

10minus1

10minus2

120573 = 05∘Cmin120573 = 10∘Cmin120573 = 20∘Cmin

Loss

fact

or ta

n 120575

(b)











Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100




(a)

Axi

al d

irect

ion


(b)










Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1




10minus4 100 104 108


10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101






1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)





minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T





log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862



2= 149


log 119886119879=119864

119877(1

119879minus1

1198790

) (6)





5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




80 m

m10 mm

50 m

m

90 mm


(a)

(b)




1003816100381610038161003816120578lowast1003816100381610038161003816 =

1003816100381610038161003816119866lowast1003816100381610038161003816

120596 120578

1015840=11986610158401015840

120596 120578

10158401015840=1198661015840

120596 (3)














Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100



T = minus6∘CT = 23∘CT = 100∘C

T = minus6∘CT = 23∘CT = 100∘C







Frequency



Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

(a)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

101

100

10minus1

10minus2

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Loss

fact

or ta

n 120575

(b)







Stor

age

loss

com

plia

nceJ

998400 J998400998400

(1M

Pa)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

10minus1

10minus2

10minus3

10minus4

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz



103

102

101

100

10minus1

10minus2

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140


f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Visc

osity

120578998400 120578

998400998400(M

Pamiddots)






Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100


(a)

Temperature T (∘C)0 20 40 60 80 120100 140

Heating rate

100

10minus1

10minus2

120573 = 05∘Cmin120573 = 10∘Cmin120573 = 20∘Cmin

Loss

fact

or ta

n 120575

(b)











Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100




(a)

Axi

al d

irect

ion


(b)










Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1




10minus4 100 104 108


10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101






1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)





minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T





log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862



2= 149


log 119886119879=119864

119877(1

119879minus1

1198790

) (6)





5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100



T = minus6∘CT = 23∘CT = 100∘C

T = minus6∘CT = 23∘CT = 100∘C







Frequency



Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

(a)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

101

100

10minus1

10minus2

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Loss

fact

or ta

n 120575

(b)







Stor

age

loss

com

plia

nceJ

998400 J998400998400

(1M

Pa)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

10minus1

10minus2

10minus3

10minus4

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz



103

102

101

100

10minus1

10minus2

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140


f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Visc

osity

120578998400 120578

998400998400(M

Pamiddots)






Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100


(a)

Temperature T (∘C)0 20 40 60 80 120100 140

Heating rate

100

10minus1

10minus2

120573 = 05∘Cmin120573 = 10∘Cmin120573 = 20∘Cmin

Loss

fact

or ta

n 120575

(b)











Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100




(a)

Axi

al d

irect

ion


(b)










Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1




10minus4 100 104 108


10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101






1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)





minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T





log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862



2= 149


log 119886119879=119864

119877(1

119879minus1

1198790

) (6)





5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Stor

age

loss

com

plia

nceJ

998400 J998400998400

(1M

Pa)

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140

10minus1

10minus2

10minus3

10minus4

f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz



103

102

101

100

10minus1

10minus2

Frequency

Temperature T (∘C)0 20 40 60 80 120100 140


f = 01 Hzf = 10 Hzf = 2 Hzf = 5 Hz

f = 10 Hzf = 20 Hzf = 30 Hz

Visc

osity

120578998400 120578

998400998400(M

Pamiddots)






Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100


(a)

Temperature T (∘C)0 20 40 60 80 120100 140

Heating rate

100

10minus1

10minus2

120573 = 05∘Cmin120573 = 10∘Cmin120573 = 20∘Cmin

Loss

fact

or ta

n 120575

(b)











Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100




(a)

Axi

al d

irect

ion


(b)










Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1




10minus4 100 104 108


10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101






1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)





minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T





log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862



2= 149


log 119886119879=119864

119877(1

119879minus1

1198790

) (6)





5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










Temperature T (∘C)0 20 40 60 80 120100 140

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

100




(a)

Axi

al d

irect

ion


(b)










Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1




10minus4 100 104 108


10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101






1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)





minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T





log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862



2= 149


log 119886119879=119864

119877(1

119879minus1

1198790

) (6)





5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101

10210110010minus1




10minus4 100 104 108


10∘C

75∘C

Stor

age

loss

mod

ulus

G998400 G

998400998400(M

pa)

103

102

101






1198661015840(119886119879120596 119879) = 119866

1015840(120596 1198790) 119866

10158401015840(119886119879120596 119879) = 119866

10158401015840(120596 1198790)

(4)





minus10

minus5

0

5

10

15

20

10 20 30 40 50 60 70

Hor

izon

tal s

hift

fact

ora T





log 119886119879= minus1198621(119879 minus 119879

0)

1198622+ (119879 minus 119879

0) (5)

where 1198621and 119862



2= 149


log 119886119879=119864

119877(1

119879minus1

1198790

) (6)





5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




5 Conclusions















References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Characterization of Shape Memory Polymer ...downloads.hindawi.com/archive/2014/250258.pdf · of the paper. Finally, the experimental and analytical (theo-retical)