Dynamic shear rheometer

Although the dynamic shear rheometer (DSR) can measure dynamic viscosity, its main use is to determine the viscous and elastic behaviour of bituminous binders at medium to high temperatures, particularly to determine the complex shear modulus (G ) and the phase angle (5) of bituminous binders when tested in dynamic (oscillatory) shear, using parallel plate geometry. Details for determining viscosity with DSR can be found in Tredrea (2007). 

All types of bituminous binders can be tested with the DSR, such as unaged, aged and recovered bituminous binders, cut-backs and bituminous binders stabilised from emulsions. 

In the DSR, the sliding plate is circular and oscillates on the horizontal plane at a preselected frequency or at a range of frequencies. The typical range of frequencies used is 0.1 to 10 FIz (0.62 to 62.83 rad/s). When testing bituminous binders for compliance to ASTM D 6373 (2007), the frequency used is 10 rad/s (1.59 Hz). 

The test may be carried out under strain control conditions or under stress control conditions. ATSM D 7175 (2008) proposes target strain or stress values, depending on the bitumen tested (original, RTFO residue or pressurised ageing vessel [PAV] residue). 

The testing temperature - ) is selected within the typical range 25°C to 85°C. When a bituminous binder is tested for compliance to ASTM D 6373 (2007), the temperature is selected from an appropriate table and is within the range 4°C to 88°C. 

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Rheological Measurements of Bitumens Using Dynamic Shear Rheometers ... 

TABLE 17.6 Effect of filler and additives in HDPE (MEI 0.48 g/10 min) on the consistency index (j/o) [zero viscosity] and power-law index (n) determined in the parallel plate (dynamic shear) rheometer... 

Dynamic shear rheometer (DSR) (Figure 4.7) Dynamic (Pa.s) Bitumen/modified bitumen... 

AASHTO T 315. 2012. Determining the rheological properties of asphalt binder using a dynamic shear rheometer (DSR). Washington, DC American Association of State Highway and Transportation Officials. 

Additionally, the American practice for specification testing or quality control of bituminous mixtures also uses the properties complex shear modulus, G, and phase angle, 5 (see Section 7.4), using either the Superpave shear tester (SST) (see Section 7.4.9) or the dynamic shear rheometer (DSR) (see Section 7.4.10). 

ASTM D 7552. 2009. Standard test method for determining the complex shear modulus (G ) of bituminous mixtures using dynamic shear rheometer. West Conshohocken, PA ASTM International. 

ASTM D6601, 2002. Measurement of cure and after cure dynamic properties using a rotorless shear rheometer. 

Experimentally, the dynamic shear moduli are usually measured by applying sinusoidal oscillatory shear in constant stress or constant strain rheometers. This can be in parallel plate, cone-and-plate or concentric cylinder (Couette) geometries. An excellent monograph on rheology, including its application to polymers, is provided by Macosko (1994). 

With automated rheometers it is relatively easy to obtain dynamic shear data than steady shear data. For this reason, the interrelationship between co and t) on one hand and y and t a on the other is of interest. The Cox-Merz rule, that is, equal magnitudes of i)a and if at equal values of y and co, respectively (Equation 5.17), was obeyed by several synthetic and biopolymer dispersions (Lopes da Silva and Rao, 1992). 

Neat polymers and their blends were studied In dynamic shear field (using RMS) and In constant shear stress field using Rheometrlc Stress Rheometer, RSR. The molecular parameters of polymers and blends were determined by Size Exclusion Chromatography in trichlorobenzene at 14O C. The morphology of freeze-fractured specimens was characterized In Scanning Electron Microscope, SEM, Jeol JSM-35CF. 

Table 17.11 shows data for neat and a rice-hulls-fllled HDPE in the steady shear flow (a cone die) and the dynamic shear. One can see that the difference in the consistency index for neat HDPE between these two experimental approaches was only 14%. However, that for the filled composite was 32%. In the presence of the coupling agent, the difference was much higher 116,400 Pa.s" (cone die) and 50,600 Pa.s" (ARES rheometer), that is, 130% difference. 

Several researchers reported viscoelastic behavior of yeast suspensions. Labuza et al. [9] reported shear-thinning behavior of baker s yeast (S. cerevisiae) in the range of 1 to 100 reciprocal seconds at yeast concentrations above 10.5% (w/w). The power law model was successfully applied. More recently, Mancini and Moresi [10] also measured the rheological properties of baker s yeast using different rheometers in the concentration range of 25 to 200 g dm. While the Haake rotational viscometer confirmed Labuza s results on the pseudoplastic character of yeast suspension, the dynamic stress rheometer revealed definitive Newtonian behavior. This discrepancy was attributed to the lower sensitivity of Haake viscometer in the range of viscosity tested (1.5 to 12 mPa s). Speers et al. [11] used a controlled shear-rate rheometer with a cone-and-plate system to measure viscosity of... 

Dynamic mechanical properties are measured to evaluate melt rheology of thermoplastics with and without additives which may modify rheological characteristics of these compositions. " Dynamic oscillatory shear rheometers are used for these purposes. Two geometries of test fixtures are used including parallel plates and cone and plate. Instrument use for these measurements must be capable of measuring forces (stress or strain) and frequency. Temperature must be controlled in a broad range and various modes of temperature sweeps should be available. Sample geometry is not specified but it should be suitable for measurement in particular experimental setup. 

Rheological measurements were performed in a stress rheometer fixture with a 2-cm cone and plate having a 1° cone angle and gap of 27 pm. Dynamic shear moduli were measured at 0.5% strain between 0.1 and 100 rad/s. Creep compliance was measured with a constant applied stress in the range of 0.1 to 5 kPa. Both measurements were performed over a series of temperatures to obtain data for time-temperature superposition. 

Figure 58 Schematic diagrams of an ER suspension under (a) off-state electric field b) on-state electric field (c), both an electric and a shear fields d) both an electric and a dynamic shear field. Two bold lines stand for electrodes and parallel-plate of the rheometer. Reproduced with permission from T. Hao, J. Phys. Chem., 102(1997)1...

There are many designs of rheometer for materials with different viscoelasticities. For example, liquids can be examined in the Couette geometry, which consists of vertical concentric cylinders, one of which rotates with the sample between the gap. Cone-and-plate and parallel disc cells are also widely used. For soft solids, oscillatory shearing between vertical parallel plates yields the dynamic shear moduli. 

Two copolymers, a poly(styrene-6-isoprene-7>-styrene) (SIS) triblock (60 wt% S Mn=100,000, Mw/Mn=1.04) and a poly(styrene-Wsoprene) (SI) diblock (70 wt% S Mn=50,000, Mw/Mn=1.05), were synthesized by anionic polymerization. The selective solvent used here was an aliphatic white mineral oil (MO) produced by Witco (380PO). Specific masses of each copolymer and MO weae dissolved in cyclohexane and cast into molds. Upon solvent evaporation, the resultant films were vacuum-dried for up to 7 h at 120 C. Steady-shear tests were performed on a Rheometrics dynamic stress rheometer (DSR) as a function of shear stress (x) to measure the solution viscosity (q), while dynamic tests were performed here to discern G and G" as functions of x, oo and temperature. 

Rheology. Dynamic and steady shear measurements were done with an Rheometric Al S rheometer. 25mm parallel plate fixtures were used for the dynamic shear experiments frequency sweeps over the frequency range O.Ol-lOOHz were made between 120 - 260lfc using film specimens. All measurements were made within the Unear viscoelastic Umit, which was determined from strain sweeps. Steady shear experiments as a function of shear rate were made between 150 - 2801C with a 25 mm cone-and-plate fixture. The shear rate range used was 0.001 to 25 s. ... 

The Weissenberg Rheogoniometer (49) is a complex dynamic viscometer that can measure elastic behavior as well as viscosity. It was the first rheometer designed to measure both shear and normal stresses and can be used for complete characteri2ation of viscoelastic materials. Its capabiUties include measurement of steady-state rotational shear within a viscosity range of 10 — mPa-s at shear rates of, of normal forces (elastic... 

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