Dynamic Shear Storage Modulus Research Articles

Assessment of the influence of electric arc furnace slag as a non-conventional filler for Nitrile Butadiene Rubber

Reinforcement of polymers by the addition of particles filler is a complex phenomenon that depends mainly on the hydrodynamic effect and a complex interplay between polymer, filler, and interfacial region. Mineral fillers are usually adopted as low-cost extenders due to their lower cost.In this study, the influence of a waste material such as electric arc furnace steel slag is assessed as filler for Nitrile-Butadiene Rubber following experimental procedures and analytical calculations adopted for traditional fillers. It was found that the slag content affects the static and the dynamic properties by increasing the material's capability to storage and dissipate energy. In addition to an important contribution of the hydrodynamic effect, the presence of an increasing immobilized rubber fraction around the slag particles (quantified by a differential scanning calorimetry analysis) plays a central role. The slag stiffens the NBR composite; the increase of static tensile and dynamic shear storage moduli was found to be consistent with the Halpin-Tsai and Guth-Gold prevision models respectively. Moreover, the non-linear dynamic behavior was found to be well-fitted by the Kraus equation models. The reinforcing ability of the slag particles as filler was confirmed by the negative slope of the Kraus plot on swelling data.

Influence of Magnetic Field and Temperature on Rheological Behavior of Magnetorheological Gel.

In this paper, the effect of temperature on rheological properties of magnetorheological (MR) gel is investigated under rotational steady shear and oscillatory dynamic shear. A kind of fluid-like MR gel (MRG) was firstly synthesized by mixing carbonyl iron powder (CIP) with polymer matrix. Then, the relationship between yield stress, normal stress of MRG and shear rate under six temperatures and four magnetic field strengths were studied by rotational shear experiments. The results demonstrate that the dependence of shear stress on temperature displays an opposite tendency in comparison with that of normal stress on temperature. Moreover, maximum yield stress, one of the most important parameter of MR materials, decreases with the increment of temperature. Under oscillatory dynamic shear test, storage and loss moduli and normal stress of MRG all increase with temperature when a magnetic field is applied, which presents a contrary trend in the absence of a magnetic field. Related mechanisms about the alternation of microstructures of MRG were proposed to explain the above-mentioned phenomena. This paper is helpful in fabricating semi-active engineering devices using MR materials as a medium.

A magnetic field- and frequency-dependent dynamic shear modulus model for isotropic silicone rubber-based magnetorheological elastomers

Both experimental and modeling studies on the dynamic shear storage and loss moduli of isotropic magnetorheological elastomers (MREs) were carried out in this work. Isotropic MREs were prepared based on silicone rubber filled with different contents of micro-sized carbonyl iron particles (CIPs). The magnetization characteristics of the prepared MREs and their dynamic shear moduli at a linear viscoelastic (LVE) strain and under different magnetic flux densities were measured. Based on the magnetization model of MREs, the magnetic dipole theory, and the quantitative analysis on the frequency-dependence of magneto-induced dynamic shear moduli, a new magneto-induced shear modulus model that was dependent on the CIP content and frequency was proposed. The model parameters can be simply determined. Combining with the generalized Maxwell viscoelastic model, that was used to describe the zero-field shear moduli of MREs, a new macroscopic magneto-viscoelastic constitutive model was developed to describe the magnetic field- and frequency-dependent shear modulus of the isotropic MREs with different CIP contents. The developed magneto-viscoelastic constitutive model was verified by comparing the model calculations with experimental data. The results showed that in the LVE strain state, the proposed magneto-viscoelastic model could accurately predict the dynamic shear storage and loss moduli of the isotropic MREs with different CIP contents in broad ranges of frequency and magnetic flux density using the unified model parameters.

Effects of Hybridized Organically Modified Montmorillonite and Cellulose Nanocrystals on Rheological Properties and Thermal Stability of K-Carrageenan Bio-Nanocomposite

Herein, hybrid k-carrageenan bio-nanocomposite films were fabricated by using two types of nanofillers, organically modified montmorillonite (OMMT), and cellulose nanocrystals (CNCs). Hybrid bio-nanocomposite films were made by casting techniques employing 4 wt% of CNCs, OMMT, and hybridized CNCs/OMMT in a 1:1 ratio. The rheological and morphological properties and thermal stability of all composites were investigated using rotational rheometry, thermogravimetry analysis, differential scanning calorimetry, field emission scanning electron microscopy, and transmission electron microscopy (TEM). The results showed that the hybrid CNC/OMMT bio-nanocomposite exhibited significantly improved properties as compared to those for the bio-nanocomposites with single fillers due to the nanosize and homogenous nanofiller dispersion in the matrix. Rheological analysis of the hybrid bio-nanocomposite showed higher dynamic shear storage modulus and complex viscosity values when compared to those for the bio-nanocomposite with individual fillers. The TEM analysis of the hybridized CNC/OMMT bio-nanocomposite revealed that more particles were packed together in the CNC network, which restricted the matrix mobility. The heat resistance and thermal stability bio-nanocomposite k-carrageenan film enhanced rapidly with the addition of hybridized CNCs/OMMT to 275 °C. The hybridized CNCs/OMMT exhibited synergistic effects due to the good affinity through interfacial interactions, resulting in the improvement of the material properties.

Thermal, Rheological, Mechanical and Morphological Behavior of High Density Polyethylene and Carboxymethyl Cellulose Blend

In this study water soluble sodium carboxymethyl cellulose (CMC) was blended with high density polyethylene (HDPE) by peroxide-initiated melt compounding technique. The compatibility of the blended polymers were carried out by silane crosslinking agent. A series of blends were prepared by varying the CMC contents up to a maximum of 50 phr. The physical properties of non-crosslinked and crosslinked blends were investigated in detail. FTIR analysis of crosslinked blend confirmed the presence of Si–O–Si and Si–O–C absorption peaks at 1050 and 1159 cm−1. Thermal stability of crosslinked blends improved as compared to its non-crosslinked congener. Rheological study of crosslinked blends illustrated high complex viscosity and dynamic shear storage modulus. The tensile strength of virgin polyethylene was 8.1 MPa whereas the maximum tensile strength of 19.6 MPa was observed in crosslinked blend. Similarly lower deformation was observed in crosslinked blends under static load. Scanning electron microscopy of crosslinked formulations also showed strong adhesion between the polymers interface. The compatibility of HDPE and CMC is attributed to both free radical and condensation reactions.

Differently-catalyzed silica-based precursors as functional additives for the epoxy-based hybrid materials

Two types of liquid pre-condensed silica-based precursors bearing epoxy groups were synthesized using the solvent-free sol-gel process of (3-glycidyloxypropyl)trimethoxysilane (GPTMS), in the presence of either basic (DABCO) or neutral (DBTL) catalyst, and further applied for modification of epoxy (DGEBA) – amine (Jeffamine™ D-230) glassy network. The prepared epoxy-silica hybrid materials were characterized by a set of methods including UV–vis, SAXS, TEM, AFM, DMTA, tensile tests, TGA and XRF. All hybrids were optically transparent regardless to the silica-based precursor type and its content showing an improvement mainly in dynamic shear storage modulus in rubbery region (up to 4.3 times), energy to break (up to ∼ 62%), elongation at break (up to ∼ 50%) and thermooxidative stability. The developed procedure is particularly suitable for preparation of fully-transparent massive bulk materials in which the presence of water and volatiles from the sol-gel is highly undesirable.

The effects of nanoclay on thermal, mechanical and rheological properties of LLDPE/chitosan blend

Abstract The objective of this study was to prepare linear low density polyethylene (LLDPE)/chitosan/closite nanocomposites by using various concentrations of LLDPE, chitosan, and closite clay mineral. The nanocomposites were then characterized for their thermal, mechanical, and rheological properties by using different analytical techniques including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), rheological characterization, tensile strength study, and scanning electron microscopy. The TGA demonstrated that crosslinked composites are thermally more stable than non-crosslinked composites. The DSC stated that the percentage crystallinity of crosslinked composites is lower than the non-crosslinked composites. It is also observed that the increasing quantity of chitosan and closite also reduces the percentage crystallinity of the prepared nanocomposites. Rheological characterization revealed that, crosslinked composites are viscoelastic in nature and have high complex viscosities (η*) and high dynamic shear storage modulus (G′), while non-crosslinked composites showed high dynamic shear loss modulus (G″). Tensile strength of crosslinked composites was much higher than non-crosslinked composites, however elongation at break (Eb) values of non-crosslinked composites are higher than crosslinked composites. The scanning electron microscopy displayed strong adhesion between matrix-filler-interphase in crosslinked composites, while some gaps were also observed in non-crosslinked composites. As a conclusion, chitosan, closite clay, and the LLDPE based nanocomposites with improved thermal, mechanical, and rheological properties can be successfully prepared by employing a peroxide-initiated melt compounding technique.

Preparation of microcellular low-density PMMA nanocomposite foams: Influence of different fillers on the mechanical, rheological and cell morphological properties

Abstract Poly(methyl methacrylate) (PMMA) nanocomposites were prepared by incorporating talc, carbon black (CB) and thermally reduced graphite oxide (TRGO) respectively. At a loading content of 5 wt %, the fillers were well dispersed within the PMMA matrix with the exception of CB. As expected, the inclusion of the respective fillers led to an increase of the tensile modulus at the expense of tensile strength and elongation at break compared to neat PMMA. The addition of TRGO (5 wt %) increased the dynamic complex shear viscosity (η*) and storage modulus (G/) of PMMA by one order of magnitude compared to talc and CB at the same concentration. Van Gurp-Palmen-plot further revealed the formation of filler network only for CB and TRGO particles. Physisorption measurements showed that TRGO and CB fillers were more CO2-phillic in comparison to talc and may have contributed to increasing the amount of CO2 retention as confirmed by sorption measurements. These features were exploited to prepare closed-cell microcellular low-density PMMA nanocomposite foams via batch-foam process.

The dynamic shear moduli of whale blubber.

Blubber is a thick adipose tissue located beneath the dermas. Its viscoelastic properties affect whale tracking tag design, hydrodynamics, and acoustical properties that can be used to study animal behavior and avoid ship strikes. Measure the dynamic shear storage and loss moduli for whale blubber at distances below the dermas for several species. Also, measure the non-collagen and collagen protein content to explore a correlation to viscoelastic properties. Blubber samples were obtained from whale strandings (humpback, sperm, and two gray) in the Pacific Northwest. Shear moduli were measured at oscillation frequencies of 0.31 Hz to 25 Hz using a rotational rheometer. Protein content was measured using a staining protocol. Storage modulus and loss modulus variation with frequency was very consistent across all samples tested. Log-linear and extended polynomials respectively had R-squared values of at least 0.96. Variation of both moduli with depth was fit reasonably well by fourth-order polynomials. Protein content trends varied with species. The samples used in this study were necrotic tissue, however the variation with frequency and to a lesser extent depth was very consistent and may have a broader applicability. Protein content was not found to correlate to moduli values.

Viscoelastic properties of uncured resin composites: Dynamic oscillatory shear test and fractional derivative model

ObjectiveIn this study we analyze viscoelastic properties of three flowable (Wave, Wave MV, Wave HV) and one universal hybrid resin (Ice) composites, prior to setting. We developed a mathematical model containing fractional derivatives in order to describe their properties. MethodsIsothermal experimental study was conducted on a rheometer with parallel plates. In dynamic oscillatory shear test, storage and loss modulus, as well as the complex viscosity where determined. We assumed four different fractional viscoelastic models, each belonging to one particular class, derivable from distributed-order fractional constitutive equation. The restrictions following from the Second law of thermodynamics are imposed on each model. The optimal parameters corresponding to each model are obtained by minimizing the error function that takes into account storage and loss modulus, thus obtaining the best fit to the experimental data. ResultsIn the frequency range considered, we obtained that for Wave HV and Wave MV there exist a critical frequency for which loss and storage modulus curves intersect, defining a boundary between two different types of behavior: one in which storage modulus is larger than loss modulus and the other in which the situation is opposite. Loss and storage modulus curves for Ice and Wave do not show this type of behavior, having either elastic, or viscous effects dominating in entire frequency range considered. SignificanceThe developed models may be used to predict behavior of four tested composites in different flow conditions (different deformation speed), thus helping to estimate optimal handling characteristics for specific clinical applications.

Nanocomposites of acrylonitrile-butadiene-styrene/montmorillonite/styrene block copolymers: Structural, rheological, mechanical and flammability studies on the effect of organoclays and compatibilizers using statistically designed experiments

Previous study with nanocomposites of acrylonitrile-butadiene-styrene copolymer (ABS) and organophylized montmorillonite clays (OMMT) investigated the effect of clay modifiers polarities on their performance. Nevertheless, the literature has shown that the use of compatibilizers plays a key role in the dispersion of OMMT in polymeric matrices. Therefore, in the present work, ABS/OMMT nanocomposites compatibilized with styrenic block copolymers prepared by melt intercalation in a twin-screw extruder was studied. Nanocomposites formulations followed a 22 factorial design having different kinds of Cloisite OMMT (30B and 20A + 30B) and of compatibilizers (SBS and SEBS- g-MA) as independent variables. Structural (X-ray diffraction) and morphological (transmission electron microscopy) analyses of the nanocomposites showed a better clay dispersion, partially exfoliated, for ABS/30B/SBS than the intercalated morphology for ABS/20A30B/SEBS- g-MA. Rheological dynamic shear tests indicated a tendency to the formation of a percolating network structure for the ABS/OMMT/SBS nanocomposites, independently of nanoclay kind. Besides, these materials presented non-dripping effect on flammability tests. ABS/OMMT/SBS nanocomposites show also the best performance in both uniaxial tensile and dynamic shear storage moduli. These results are probably due to improved affinity between components. In conclusion, among the styrene block copolymers, SBS compatibilizer is more effective than SEBS- g-MA to improve the properties of ABS/OMMT-based nanocomposites.

Thermal and rheological effects of sepiolite in linear low‐density polyethylene/starch blend

AbstractEffect of different concentrations of sepiolite on thermal and rheological properties of linear low‐density polyethylene/starch blend was investigated. Vinyl trimethoxy silane was used as compatibilizing and crosslinking agent. The composites were produced by peroxide‐initiated melt mixing technique. Improved thermal stability and tensile strength were observed in crosslinked formulations. Maximum tensile properties were observed in composites containing 2 parts per hundred (phr) sepiolite and 15 phr starch. Rheological study of crosslinked composite showed a linear viscoelastic behavior with high complex viscosity and dynamic shear storage modulus. Scanning electron microscopy also revealed that silane has improved the dispersion of filler and interaction among the polymer and filler interphase. These results suggest that the presence of sepiolite act as an effective filler to enhance the thermal and rheological properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci, 2013

Effect of Fiber Loading and Compatibilizer on Rheological, Mechanical and Morphological Behaviors

This study presents the composites prepared by melt blending based on high-density polyethylene, containing various amounts of kenaf fiber loadings and polyethylene-grafted maleic anhydride (PE-g-MA) in an internal mixer were prepared and investigated. Fourier transform infrared spectroscopy was used to characterize both untreated and treated ke- naf fibers. A rheological study of the composites showed a high complex viscosity and dynamic shear storage modulus between untreated and treated composites and composites with compatibilizer. A mechanical test showed that the ten- sile strength and tensile modulus were optimal with 20% fiber loading but decreased with 30% fiber loading for both the untreated and treated composites. The composite with PE-g-MA showed an improved mechanical strength. This phenomenon is due to an increase in the interfacial adhesion between the fiber and matrix leading to an improvement in the compatibility of the blend. Treatment of the kenaf fiber improved in the mechanical and impact strengths in com- parison to the untreated kenaf composites. This behavior was supported by a morphology analysis of the fractured sur- faces revealed that strong interfaces were formed on addition of the compatibilizer.

The unidirectional glass fiber reinforced furfuryl alcohol for pultrusion. II. Correlation of processing parameters for optimizing the process

AbstractUnidirectional glass fiber reinforced furfuryl alcohol (FA) composites have been prepared by the pultrusion processes. The optimum processing parameters of the glass fiber reinforced FA composites by pultrusion has been studied. The effects of the optimum processing parameters on the properties (flexural strength, flexural modulus, notched Izod impact strength, glass transition temperature (Tg), dynamic shear storage modulus (E'), shrinkage ratio, and roughness) investigated including die temperature, pulling rate, postcure temperature and time, and filler type and content. Results show that the pultruded composites possessed various optimum pulling rates at different die temperatures. On the basis of the DSC diagram, the swelling ratio and the mechanical properties of pultruded composites, the optimum die temperature can be determined. The mechanical properties and Tg increase at a suitable postcure temperature and time. Furthermore, the properties which decrease due to the degradation of pultruded composites for a long postcure time will be discussed. The mechanical properties of pultruded composites reach a maximum value at various filler content corresponding to the talc and calcium carbonate, respectively, and then decreased. When the fillers are added to the pultruded glass fiber reinforced FA composites, the shrinkage ratio of composites become smaller, and the surface of composites became smooth. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Thermal, rheological, mechanical and morphological behavior of HDPE/chitosan blend

A peroxide-initiated melt compounding technique was used to graft and crosslink the high density polyethylene/chitosan blend using vinyl triethoxysilane. Different percentage of chitosan (up to maximum of 35%) was added in HDPE/chitosan blends. The physical and functional properties of the crosslinked HDPE/chitosan blends were investigated and compared with its non-crosslinked congener. IR spectrum of crosslinked blend confirmed the presence of Si–O–Si and Si–O–C absorption peaks at 1020 cm −1 and 1105 cm −1. Increased gel content was obtained with increasing chitosan loading whereas percentage crystallinity was decreased. Rheological study of crosslinked blends showed linear viscoelastic behavior with high complex viscosity and dynamic shear storage modulus. Tensile strength of crosslinked HDPE was 9.3 MPa and it was increased by threefold to 27.4 MPa in crosslinked HDPE/chitosan blends containing 35% chitosan contents. Similarly lower deformation was observed in crosslinked blends under static load. Scanning electron microscopy revealed good adhesion between matrix–filler interphase.

Longitudinally propagating traveling waves of the mammalian tectorial membrane

Sound-evoked vibrations transmitted into the mammalian cochlea produce traveling waves that provide the mechanical tuning necessary for spectral decomposition of sound. These traveling waves of motion that have been observed to propagate longitudinally along the basilar membrane (BM) ultimately stimulate the mechano-sensory receptors. The tectorial membrane (TM) plays a key role in this process, but its mechanical function remains unclear. Here we show that the TM supports traveling waves that are an intrinsic feature of its visco-elastic structure. Radial forces applied at audio frequencies (2-20 kHz) to isolated TM segments generate longitudinally propagating waves on the TM with velocities similar to those of the BM traveling wave near its best frequency place. We compute the dynamic shear storage modulus and shear viscosity of the TM from the propagation velocity of the waves and show that segments of the TM from the basal turn are stiffer than apical segments are. Analysis of loading effects of hair bundle stiffness, the limbal attachment of the TM, and viscous damping in the subtectorial space suggests that TM traveling waves can occur in vivo. Our results show the presence of a traveling wave mechanism through the TM that can functionally couple a significant longitudinal extent of the cochlea and may interact with the BM wave to greatly enhance cochlear sensitivity and tuning.

Effect of crosslinking on the mobility of PDMS filled with polysilicate nanoparticles: Positron lifetime, rheology and NMR relaxation studies

We study the effect of adding trimethylsilyl-treated polysilicate nanoparticles (Rg∼2.2nm) to crosslinked poly(dimethylsiloxane) (PDMS) elastomers above the entanglement molecular weight. The results are compared to un-crosslinked PDMS of a similar molecular weight, reported in previous studies and filled with the same polysilicate nanoparticles.Three techniques are used and compared to assess the enhancement or reduction in mobility with addition of filler: positron annihilation lifetime spectroscopy (PALS), rheology and nuclear magnetic resonance (NMR) spin–spin relaxation (T2) measurements. PALS measurements do not show any clear effect of the filler on the mobility of the chains, as assessed by the size of free volume holes, but reveal a net increase in free volume with temperature increase (from 30°C to 60°C). A reduction in the dynamic shear storage modulus (measured at 1rads−1) is observed in the filled network relative to the unfilled polymer (from 63kPa without filler to 44kPa with 40w/w% filler), attributed primarily to a partial inhibition of the chemical crosslinking reaction by the particles. The NMR relaxation measurements, instead, show a reinforcement of the polymer network with increasing addition of polysilicate particles, as revealed by the faster T2 decays at higher filler loadings, caused by increasing polymer bridging and particle flocculation. Similar trends are observed at higher temperatures (up to 80°C), with a higher overall mobility. The apparent disagreement between rheology and NMR stems from the fact that rheology reflects bulk mobility and is primarily sensitive to chemical crosslinks in the network, while NMR probes segmental dynamics, which are affected by the presence of particles.In un-crosslinked PDMS instead, both rheology and NMR show an initial increase in mobility at low filler content, followed by reinforcement with further particle addition. These results strongly suggest that entanglements and filler-induced packing disruption, rather than free volume, play a major role in polymer dynamics.

The effect of temperature on viscoelastic properties of glass ionomer cements and compomers

The objective of this study was to determine the viscoelastic properties of different types of glass ionomer cements (GICs) and compomers under varying temperature conditions found in the mouth. The materials tested were a conventional GIC (Aqua Ionofil U), a resin modified GIC (Fuji II LC), a highly viscous GIC (Voco Ionofil Molar), and two polyacid modified composite resins/compomers (Glasiosite and Dyract Flow). Six groups of four specimens were prepared from each material. One group was stored dry for 24 h and was subsequently tested dry at 21 degrees C. Each of the remaining five groups was stored for 24 h in distilled water at the temperatures 21, 30.5, 37, 43.5, and 50 degrees C, respectively, and was subsequently tested at that temperature. Shear storage modulus and loss tangent were determined by conducting dynamic torsional loading. Static shear moduli were determined by applying a constant torque (below the proportional limit of the materials) for 10 s and recording the angular deformation of the specimens. Data were analyzed by ANOVA and Duncan's test (alpha= 0.05). It was found that the viscoelastic properties varied significantly (p < 0.05) across the different materials. The compomer Glasiosite, with the highest filler content, and the highly viscous GIC Voco Ionofil Molar exhibited the highest elastic moduli and lowest loss tangents. Viscoelastic properties varied also significantly (p < 0.05) with temperature levels, but changes in the tested region were not indicative of a glass transition. Dynamic shear storage moduli were highly correlated to the static ones. Storage in water lowered the values of elastic moduli.

Dynamic and static elastic moduli of packable and flowable composite resins and their development after initial photo curing

The purpose of this study was to evaluate the dynamic (storage) shear modulus and the static shear modulus of elasticity of packable and flowable composite resins and to investigate their development after initial photo-curing. Three pairs of a packable versus a flowable composite and a microfill composite resin were tested (Alert/Flow It, Filtek P60/Filtek Flow, Admira/Admira Flow, A 110). Cylindrical specimens (0.85 mm x 18 mm) were made for each material. All specimens were conditioned and tested dry at 21 degrees C. The specimens were tested at 30 min, 24h and 1 week after the end of photo curing. Storage shear modulus and loss tangent were determined by conducting dynamic torsional loading in the frequency range from 1 to 150 Hz. Static shear modulus measurements were made by applying a constant load (below the proportional limit of the materials) for 10s and recording the angular deformation of the specimens. Data were analyzed by ANOVA and Duncan's Post hoc test (alpha=0.05). Storage shear moduli (at 1 week measurement) ranged from 3.39 to 9.67 GPa, and loss tangents from 0.0735 to 0.0235; static shear moduli ranged between 2.66 and 9.80 GPa. High values of elastic moduli and low tandelta values were obtained with packable composites, while low moduli values were obtained with flowable composites. Statistically significant (alpha=0.05) differences were recorded between materials of the same category. Storage time, 24h and 1 week after initial polymerization, resulted in significant increases in both moduli of elasticity. Dynamic shear storage moduli were highly correlated to the static ones (r(2)=0.92; P<0.05). The results of the aging studies showed that the rigidity of these materials increases significantly even 1 week after the clinician turns off the curing unit.

Impedance spectroscopy: an accurate method of differentiating between viable and ischaemic or infarcted muscle tissue.

The object of the paper is to present results that show that impedance spectroscopy is an accurate method of assessing the condition of muscle tissue. Specimens of muscle tissue were excised from 36 Atlantic salmon and subjected to impedance spectroscopy measurements made at intervals during an 8h period of ischaemia and necrosis. These measurements were conducted for three different temperatures and for both the longitudinal and the transverse orientations of the muscle fibres. The specimens were also subjected to ATP, pH and visco-elastic measurement and analysis to establish the degree of correlation between changes in these quantities and impedance spectroscopy parameters due to ischaemia. It was concluded that the mean relaxation time, tau(c) was the impedance spectroscopy parameter that best described the changes taking place in the muscle tissue during the post-mortem period, decreasing by 60-76% during the 8h. This was the case for all three temperatures and for both orientations. Furthermore, the muscle tissue changes due to ischaemia, as reflected in the decrease in the mean relaxation time tau(c), were highly correlated with changes in the tissue ATP, pH and dynamic shear storage modulus G'.