Rheometric Dynamic Analyzer

Fig. 7 The Payne Effect measured on a rheometrics dynamic analyzer (RDA II), using a 10 Hz strain sweep from 0.05% to 10% strain, 65° C, on a typical tire tread containing 50phr HAF black. (View this art in color at www.dekker.com.)...

RDAII Dynamic Analyzer C 10-6-500d 102-10s Rheometric Scientific... 

The Rheometric Scientific RDAII dynamic analyzer is designed for characterization of polymer melts and solids in the form of rectangular bars. It makes computer-controlled measurements of dynamic shear viscosity, elastic modulus, loss modulus, tan 8, and linear thermal expansion coefficient over a temperature range of ambient to 600°C (—150°C optional) at frequencies 10-5 —500 rad/s. It is particularly useful for the characterization of materials that experience considerable changes in properties because of thermal transitions or chemical reactions. 

Rheological measurements were carried out at a Dynamic Analyzer Rheometer RDA II from Rheometrics. Parallel plate geometry with a plate diameter of 25 mm was used to perform the tests where thin films of materials of 1 mm thickness were inserted. To ensure the viscoelastic... 

Mechanical Properties. Dynamic mechanical properties were determined both in torsion and tension. For torsional modulus measurements, a rectangular sample with dimensions of 45 by 12.5 mm was cut from the extruded sheet. Then the sample was mounted on the Rheometrics Mechanical Spectrometer (RMS 800) using the solid fixtures. The frequency of oscillation was 10 rad/sec and the strain was 0.1% for most samples. The auto tension mode was used to keep a small amount of tension on the sample during heating. In the temperature sweep experiments the temperature was raised at a rate of 5°C to 8°C per minute until the modulus of a given sample dropped remarkably. The elastic component of the torsional modulus, G, of the samples was measured as a function of temperature. For the dynamic tensile modulus measurements a Rheometrics Solid Analyzer (RSA II) was used. The frequency used was 10 Hz and the strain was 0.5 % for all tests. 

Mechanical Properties. To reveal the reinforcing effect of liquid crystalline polymer microfibrils on the mechanical properties of the films both their dynamic torsional moduli and dynamic tensile moduli have been studied as a function of temperature using a Rheometrics Mechanical Spectrometer (RMS 800) and a Rheometrics Solids Analyzer (RSA II), respectively. For comparison purpose the modulus of neat matrix polymers and, in some cases, the modulus of carbon fiber and Kevelar fiber reinforced composites has also been measured. 

A sample of the gel was then mounted between 50 mm parallel plates of a Rheometrics Dynamic Mechanical analyzer. The gap between the plates was then reduced to 1 mm and the excess polymer trimmed off. Dynamic scans were then performed at room temperature (G and G as a function of frequency) at 50% strain. 

Viscoelastic behavior can be viewed as three fundamental modulus characteristics G orE =complex modulus, G or E = storage or dynamic modulus, and G" or E" = loss or viscous modulus. The moduli are related by the angle of phase lag 5 in stress-to-strain phase lag. They are derived from measurements of the complex modulus and phase angle 8 relationships of stress to strain, by dynamic mechanical analysis (DMA) using a Rheometric Solids Analyzer, RSA, supplied by TA Instruments [19]. Further information on loss modulus, storage modulus, and DMA is found in Chap. 2, Products and Designs, and Chap. 3, Properties. ... 

To increase the viscosity of polymer blends, additives [such as traditional fire retardants (mainly oxides) and, more recently, nanoclays] are added to polymer blend systems. The present authors recently conducted dynamic rheological measurements for the EVA/LDPE nanocomposite, as reported in [27]. Figure 8.3 (a) and (b) compare the complex viscosity of the EVA/LDPE blend with and without nanoclay as a function of frequency and temperature, respectively. Measurements were carried out on 1 mm-thick samples using a Rheometrics RDA n Dynamic Analyzer rheometer. The frequency-sweep tests were conducted from 0.1 to 100 rad/s with constant temperature (140 °C) and strain amplitude (1%). Eor the temperature-sweep measurements, samples were heated from 300 to 530 °C (15 °C/min) under nitrogen with constant frequency (10 rad/s) and strain amplitude (10%). In both experiments, there is a significant increase of viscosity above that for the neat... 

Dynamic Mechanical Thermal Analyzer (DMTA) c 10-" -2 X 10" 10 -10" Rheometric Scientific, Inc., Piscataway, N.J. 

Small deformation dynamic mechanical analysis on compressed or blown fdms was done using a Rheometrics Scientific RSA II Solids Analyzer. Samples were tested using an initial applied force of 150 grams, an applied strain of 0.1%, and were heated from -100°C to 200°C at 10°C/min. A triplicate set of tests were performed for each samples... 

Dual Cure. Films were prepared for Dynamic Mechanical Analysis (DMA). All films were cast on release paper with a 4.5 mil draw down bar, and partially cured with two 200 watt/inch lamps at half power and a belt speed of 200 ft/min. The films were intentionally under cured to facilitate cutting with minimal flaws. After the films were cut into ii-inch test pieces, they were cured with two 200 watt/inch lamps at 100 ft/min, equal to 260 millijoules/cm dose. The instrument used for the DMA work was a Rheometrics RSA II Solids Analyzer. All tests were made at a frequency of 11 hz with a nominal strain of 0.05%, under nitrogen. Both temperature scans, at 2°C/minute, and isothermal runs were made. 

The instrument for determination of shear moduli was a Rheometric Scientific dynamic mechanical thermal analyzer, model DMTA V. Round shear sandwich geometry was used. The instrument was inverted so that the sandwich fixtures and sample were in water. A water-jacketed 1000 mL Pyrex cylinder supplied by Rheometric Scientific allowed control of temperature with a circulating temperature bath. A sinusoidal linear shear was applied by moving a flat plate between two identical disk-shaped samples over a specified range of frequencies. The two identical disk-shaped samples were sandwiched between the moving plate and two 12 mm diameter plates (called studs) fastened to a frame. The dynamic frequency sweeps to obtain the loss shear modulus, G", from 0.16 Hz to 318 Hz were reported in log scale. For our purposes the applied initial static force was 0.05 N. Sample size was 12 mm diameter and 0.7 mm thickness. The sample was equilibrated at 40°C for 12 hours prior to starting the series of measurements. Shear moduli were measured from high to low temperature with an equilibration time of 2 hours at each temperature. The sequence of measurements was 40°C, 30°C, 25°C, and 15°C. 

Thermal dynamic mechanical analysis (TDMA) was done on a Rheometric Scientific RSA II Solids Analyzer (Piscataway, NJ) using a film testing fixture (5, 6). A nominal strain of 0.1% was us in all cases, with an applied frequency of 10 rad/sec (1.59 Hz). A temperature ramp of 10°C/min was used in all cases. Nominal dimensions of the samples were 6.4 mm x 38.1 mm. The gap between the jaws at the beginning of each test was 23.0 mm. Data analyses were carried out using Rheometrics RHIOS and Orchestrator software. 

All specimens for the mechanical properly measurement were preheated at 60 C for 24 hours in order to prevent reverse reaction (hydrolysis) from the moisture during the processing, and compression molded to a sheet having 1mm thickness and 5 mm width at the temperature of 30°C above its T. Tensile tests were performed using universal testing machine (UTM, Lloyd LR 50K), and dumbbell type specimens according to ASTM D-638 were used with a crosshead speed of 100 mm/min. For dynamic mechanical property measurements, dynamic mechanical thermal analyzer (DMTA, Rheometric Scientific, Mark IV) was employed and specimen with 1mm thickness and 5 mm width sheet was used. All tests were conducted at a 3°C/min heating rate and 1.1 Hz. 

Instead of attempting to assess the resistance of a composition to a flexural strain by accelerating the amplitude of the strain, the frequency of deformation can be increased. Miniatorized versions of the three-point and four-point apparatos of are used in dynamic mechanical analyzers, such as supplied by Rheometrics and others. Flexural modulus can be determined versus frequency over a broad tempera-tore range, before and after heat aging or service in the field. Procedures are covered in ASTM Publication STP1402. 

Figures 12.14 and 12.15 show data obtained in tension using cast films oscillated with the help of an electromagnetic reed vibrator operating at resonance. Commercial instruments available today use forced vibrations without resonance. These are desirable because they allow the user to vary temperature and frequency over wide intervals. For example, in the dynamic mechanical thermal analyzer (DMTA), an instrument made by the Rheometrics Company, a bar sample is clamped rigidly at both ends and its central point is vibrated sinusoidally by the drive clamp. The stress experienced by the sample is proportional to the current supplied to the vibrator. The strain in the sample is proportional to the sample displacement and is monitored by a nonloading eddy current transducer and a metal target on the drive shaft. In this instrument, the...

A Solids Analyzer RSA II (Rheometric Scientific) was used to measure the storage and loss moduli as a fimction of temperature. The 3-point bend fixture was used to mount the samples and 4 C temperature steps were used. All experiments were performed with a 1 Hz frequency, 0.03% strain, and with static force tracking dynamic force. 

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