Dynamic spectrometer

Rheometric Scientific markets several devices designed for characterizing viscoelastic fluids. These instmments measure the response of a Hquid to sinusoidal oscillatory motion to determine dynamic viscosity as well as storage and loss moduH. The Rheometric Scientific line includes a fluids spectrometer (RFS-II), a dynamic spectrometer (RDS-7700 series II), and a mechanical spectrometer (RMS-800). The fluids spectrometer is designed for fairly low viscosity materials. The dynamic spectrometer can be used to test soHds, melts, and Hquids at frequencies from 10 to 500 rad/s and as a function of strain ampHtude and temperature. It is a stripped down version of the extremely versatile mechanical spectrometer, which is both a dynamic viscometer and a dynamic mechanical testing device. The RMS-800 can carry out measurements under rotational shear, oscillatory shear, torsional motion, and tension compression, as well as normal stress measurements. Step strain, creep, and creep recovery modes are also available. It is used on a wide range of materials, including adhesives, pastes, mbber, and plastics. 

All the viscoelastic measurements were carried out in the Rheometrics Dynamic Spectrometer RDS-770 at a frequency of 1Hz, a strain of 0.1%, and a temperature range of -140° to 140°C incremented every 2 degrees. The Texas Instrument Terminal Silent 700 was tapped to provide a hookup to an IBM 308X main frame computer located some miles away. The output of the Rheometrics unit was converted to a data file to be used in conjuc-tion with SAS (1). All statistical manipulations, software developments, and the necessary graphics that are reported here were carried out with the aid of SAS. 

Rheological Experiments. Melt viscosity and low-strain oscillatory experiments were performed on a Rheometrics RDS-7700 dynamic spectrometer equipped with a 0.2-2.0-g-cm torque transducer. The samples were mounted on 25-mm-diameter parallel-plate fixtures with a gap of 0.5 mm. Prior to each scan, samples were heated to 50 °C and then cooled slowly to room temperature. Steady-shear... 

Dynamic Mechanical Properties. Dynamic mechanical properties were measured with a Rheometrics Dynamic Spectrometer Model 7700 in the torsional rectangular mode. Temperature sweeps were run from -160 to 34O C using a strain of 10% and frequencies of 1, 10, and 100 radians per second (rad/s). Data was obtained at 5 degree temperature increments with at least a one minute thermal equilibration time at each temperature. Only the 10 rad/s data are reported in this paper. 

Figure 11 compares the low-temperature modulus characteristics of representative fiber-coating (buffer) materials of the three types described earlier. The figure depicts the dynamic tensile modulus as a function of frequency at -40 °C. The data were obtained on films of the materials by using a Rheometrics rotational dynamic spectrometer operated over the frequency range from 10 to 10 rad/s. Curves obtained at different temperatures were shifted both horizontally and vertically in accord with established linear... 

In a rheometric dynamic spectrometer such as RDS7700 manufactured by Rheometrics, Inc., the torque and normal force generated in response to an imposed motion are measured by a transducer. A microcomputer determines stresses from these values with measured sample motion to calculate strains and viscoelastic functions such as G, G", and tan d [12]. 

Operations Manual of Rheometric Dynamic Spectrometers, RDS-7700, Rheometrics, Inc., New Jersey. 

Rheological experiments were performed with a Rheometrics RDS-II and a Philips selfmade dynamic spectrometer. Circular samples for this measurement were cut from the compression moulded sheets. 

Next, we would like to explain some of the details of our experimental technique because there are difficulties in handling these amorphous systems, most of which are pressure-sensitive adhesives at room temperature. For our work we used a dynamic spectrometer manufactured by Rheometrics Inc. (RDS). Both the parallel-plate and torsional-rectangular sample geometries were used initially, and we employed both temperature and frequency sweeps to obtain our data. The details of our testing technique are presented below. 

We first examined the dynamic mechanical properties of various elastomers which are commonly used for PSA applications. The dynamic mechanical properties of these elastomers were characterized using the parallel-plate mode of the Rheometrics dynamic spectrometer (RDS). The measurement of dynamic mechanical properties was carried out on bulk or dried latex samples. Caution should be taken during the drying step to avoid crosslinking or degradation. All the temperature scan data of rubber-resin blends in this paper were measured at 10 rad/sec with less than 2% strain. 

A Rheometrics Dynamic Spectrometer, RDS-7700, was used for measurement of dynamic mechanical properties. The samples were cut to 13 by 64 mm and were 1.3 to 1.6 mm thick. A liquid nitrogen controller was used to achieve the desired temperature. Measurements were taken at 10° temperature increments, with an equilibration time of two minutes at each temperature. The range studied was from -100 to 160°C, with a strain setting of 1 percent and a rate of 6.28 radians per second. 

The dynamic mechanical properties of both TPUs were determined with a Rheometrics ARES dynamic spectrometer. Rectangular samples (25 mm x 12.7 mm x 2.0 nun) were torsionally stressed at 1 Hz with a strain of 0.1%. Storage modulus (G ) and loss modulus (G") were determined as a function of temperature from -lOOTC to 200KC in 3fC increments with 1 minute equilibrium intervals. 

The dynamic rheological properties of both TPUs in the melt were determined with a Rheom cs ARES dynamic spectrometer with a 25 mm parallel plate configuration. Circular samples (2mm gap) were stressed at 1 Hz with a strain of 1%. Complex viscosity (t] ) was determined as a function of temperature from lOOTC to 250KC at 5fC/min. This was immediately followed by a cooling scan back to 50°C at the same rate. 

---