Rheometrics Mechanical Spectrometer

Striking support of this contention is found in recent data of Castro (16) shown in Figure 14. In this experiment, the polymerization (60-156) has been carried out in a cone-and-plate viscometer (Rheometrics Mechanical Spectrometer) and viscosity of the reaction medium monitored continuously as a function of reaction time. As can be seen, the viscosity appears to become infinite at a reaction time corresponding to about 60% conversion. This suggests network formation, but the chemistry precludes non-linear polymerization. Also observed in the same conversion range is very striking transition of the reaction medium from clear to opaque. 

Rheological Properties Measurements. The viscoelastic behavior of the UHMWPE gel-like systems was studied using the Rheometric Mechanical Spectrometer (RMS 705). A cone and plate fixture (radius 1.25 cm cone angle 9.85 x 10" radian) was used for the dynamic frequency sweep, and the steady state shear rate sweep measurements. In order to minimize the error caused by gap thickness change during the temperature sweep, the parallel plates fixture (radius 1.25 cm gap 1.5 mm) was used for the dynamic temperature sweep measurements. 

Dynamic melt viscosity studies on the star blocks and a similar triblock were carried out using a Rheometric Mechanical Spectrometer (RMS) (Rheometrics 800). Circular molded samples with -1.5 mm thickness and 2 cm diameter were subjected to forced sinusoidal oscillations (2% strain) between two parallel plates. The experiment was set in the frequency sweep mode. Data were collected at 180 and 210 °C. 

The dynamic melt viscosity measurements of select star blocks and a similar triblock were carried out on a rheometric mechanical spectrometer, RMS. Circular molded samples of 2 cm diameter and -1.5 mm thickness were subjected to forced sinusoidal oscillations. Dynamic viscosities were recorded in the frequency range of 0.01-100 rad/s at 180 °C. Figure 10 shows the complex viscosities of two select star blocks and a similar linear triblock. The plots showed characteristic behavior of thermoplastic elastomers, i.e., absence of Newtonian behavior even in the low frequency region. The complex viscosity of the star block... 

Example 11.1 Chain Modification (Branching and Partial Cross-linking) of PET with Triglycidyl Isocyannrate (TGIC) Dhavalkikar (39) conducted the reaction cited in the Example title on samples placed between the rheometrics mechanical spectrometer (RMS) parallel disks in the temperature-controlled chamber under nitrogen. He followed the reaction dynamics chemorheologically by measuring, in-line, the in- and out-of-phase dynamic moduli G (t) and G"(t) they are indicative of the elastic and viscous nature of the molten reactive samples. 

Viscoelastic experiments were conducted on a Rheovibron DDV-II-C apparatus and on a Rheometrics Mechanical Spectrometer. The Rheovibron studies were carried out in tension on cured samples at 3.5, 11,... 

The authors are grateful to Paul Rempp of the Centre de Recherches sur les Macromolecules, Strasbourg, France, for generously supplying the diblock copolymers used in this study. Homopolymers were supplied by Shell Chemical and Phillips Petroleum. Support for this research was provided by the Office of Naval Research and by the Petroleum Research Fund, administered by the American Chemical Society. The Rheometrics Mechanical Spectrometer used in this study was obtained through the support of the RIAS Program of the National Science Foundation. 

The Torsion Impregnated Cloth Analysis (TICA) measurements utilized here were conducted under nitrogen with a Rheometrics Mechanical Spectrometer (RMS) according to the procedures described in the previous paper (7). 

The TICA specimen preparation procedure has been described elsewhere (4). The mechanical measurements were made with the Rheometrics Mechanical Spectrometer (RMS) which measures the in-phase and out-of-phase stress response (a and b component respectively) of a specimen being subjected to a sinusoidal shear strain. The instrumental set-up was reported by Lee (6). The frequency of the strain function was kept constant at 1.6 Hz (10 rad/sec). All temperature scan experiments were scanned at 2 C/min rate. The temperature was scanned down at the same rate when the maximum temperature was reached. 

Rheometrics Mechanical Spectrometer Operating Manual, Rheometrics Inc., 1974. 

The rheological experiments were performed on a Rheometrics Mechanical Spectrometer RMS 705F. Cone and plate geometry was used in order to generate a homogeneous shear history throughout the sample, a prerequisite in order to analyse transient behaviour. All experiments have been performed at 293K. 

Rheology. The rheological properties of the blends and their components were determined on a Rheometrics Mechanical Spectrometer (RMS 800). Three kinds of dynamic oscillatory measurements (i.e. temperature, time, and frequency sweeps) were carried out. All experiments were done by using a parallel plate attachment with a radius of 12.5 mm and a gap setting from 1.2 to 1.8 mm. There was no significant dependence of the experimental results on the gap setting. 

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. 

Figure 9. Viscosity of letterpress ink and oils (described in Figure 8) measured as a function of shear rate in a Rheometrics Mechanical Spectrometer with cone and plate fixtures and a cone angle of 2°20 (22).

The dynamic shear storage modulus (G1) and loss modulus (G") were measured from -150° to 50°C using the forced torsion fixture on a Rheometric Mechanical Spectrometer (RMS). When the storage modulus dropped below 10 Pa. this fixture became insensitive. For moduli less than 10 Pa, the parallel plate fixture with serrated disks was used. The parallel plate fixture was used to extend the dynamic mechanical measurements to high temperatures. Degradation above about 250°C dictated this temperature as an upper limit for RMS measurements. Further discussion of equations and use of these fixtures are given elsewhere (2,8). 

A special unit, equipped for fight scattering measurements, was attached to a Rheometrics Mechanical Spectrometer with cone and plate to follow the transitional events during shearing of polymer blend melts. The predictions of p obtained by the proposed model were found to be in a reasonable agreement with the experimental observations for poly(methyl methacrylate) blends with either 8 or 10 wt% polystyrene, PMMA/PS. The most interesting finding that came out of this work was that, both theoretically and experimentally, under steady-state flow condi-... 

Viscosity measurements were made at 50 C on a Rheometrics Mechanical Spectrometer Model RMS-7200 in steady shear mode with the cone and plate geometry. 

A differential scanning calorimeter (DSC) (Du Pont 910) was used to monitor the Tg s of the epoxies. The heating rate was 10°C/min. The dynamic mechanical properties of the epoxies were monitored by a Rheometrics mechanical spectrometer (Model RMS-7200). Epoxy specimens with dimensions of 6.4x1.3x0.3 cm were torqued at an oscillating frequency of 2.0 Hz. The shear storage (G ) and loss (G") moduli and tan 5 were determined from -160°C to +140 C. The densities of the epoxies were performed on 1x1x0.3 cm epoxy specimens that were immersed in methyl ethyl ketone for seven days. The weights (w) and volumes (v) of the specimens were measured prior to (wj and V ) and after (wf.and Vf) immersion and the swelling ratio v /v determined. 

Two commercial viscometers were used at higher shear stresses a Rheometrics Mechanical Spectrometer with sensitive transducer (data kindly provided by P. J. Whitcomb of General Mills Chemicals Co.), and a Contraves instrument (data kindly provided by W. Gale and B, Boseck of Exxon Production Research Co.). Viscosity standards from Cannon Instrument Co. were used to check the Contraves instrument. 

Other rotating instruments include ones with three point loading [6], for which examples of correlation with extrusion behavior have been given [10) and an annular trough arrangement fitted to a Rheometrics mechanical spectrometer (11). Fitting an annular shear cell to a torque rheometer is also possible [8]. 

A series of viscoelastic fluids based on SE-30 (General Electric, polydimethyl siloxane gum, = 450,000) were used in the evaluation of the Differential Rheometer (DR) for viscoelastic fluids. The samples were prepared with a serial dilution technique starting with a 8.874% mixture of low molecular weight PDMS (Scientific Polymer Products, Inc., = 103,400) in SE-30. Portions of this mixture were serially diluted with pure SE-30 to obtain four different viscoelastic fluids. The samples were characterized on a Rheometrics Mechanical Spectrometer (RMS) in the oscillating parallel plate mode. The measurements were taken at 22 C using 25-mm fixtures and a strain amplitude of less than 5 percent. 

The results of the experimental characterization of the viscoelastic fluid samples with the Rheometrics Mechanical Spectrometer (RMS) are presented in Table 1. The reported standard deviations for each sample at a given frequency is for three independent. sample loadings. Since the frequency was swept for a given sample loading, the observations at different frequencies cannot be considered strictly independent. The theoretical equations for the opposed squeeze flow of two viscoelastic fluids were tested by varying sample modulus, thickness and strain amplitude. In addition, the ability of the DR to resolve small differences was compared with that found with the RMS. 

A Rheometrics Mechanical Spectrometer Model RMS-605 was used for frequency scanning, forced driven mechanical testing. 

Two liquid crystalline copolyesters of 60 mole % PHB/PET and 80 mole % PHB/PET were used in this study. These samples were supplied by Tennessee Eastman and the properties are given elsewhere. Rheological properties were measured under various conditions of shear and thermal history using a 0.1 radian cone and plate attachment of a Rheometrics Mechanical Spectrometer (RMS). Various types of flow histories were used in this study and these are listed below ... 

The Rheometrics Mechanical Spectrometer we originally used was a standard laboratory instrument, as is the Weissenberg Rheogoniometer, which could also have been used at that time. The polymers were also readily available, the solvent was not exotic or toxic, and measurements were made at room temperature with no particular precautions. The three techniques which we employed to stretch the shear rate range were ... 

The design of the Rheometrics Mechanical Spectrometer of the era was helpful, as it allowed rapid reloading and trimming of excess sample. 

The dynamic mechanical data were obtained in two different modes. The low temperature data (-140°C to 20 C) were obtained in the torsion mode on a Rheometrics System IV at 10 rad/sec. The high temperature data were obtained in the parallel plate mode on a Rheometrics Mechanical Spectrometer at 10 rad/sec. 

Dynamic Mechanical Testing. Composite samples were tested in the dynamic torsional mode of a Rheometrics Mechanical Spectrometer (RMS 800) using an angular frequency of 10 rad/s, a strain of 1%, and a nitrogen atmosphere. The dynamic storage and loss moduli of 45 mm long rectangular samples (8 mm x 1.5 mm) were recorded as a function of temperature. The temperature was increased from 50 to 250 C at constant rates and then decreased at the same rates. 

---