Rheometrics dynamic mechanical analysis

Thermal analysis, moisture uptake and dynamic mechanical analysis was also accomplished on cured specimens. Thermal analysis parameters used to study cured specimens are the same as those described earlier to test resins. The moisture uptake in cured specimens was monitored by immersing dogbone shaped specimens in 71 C distilled water until no further weight gain is observed. A dynamic mechanical scan of a torsion bar of cured resin was obtained using the Rheometrics spectrometer with a temperature scan rate of 2°C/minute in nitrogen at a frequency of 1.6Hz. The following sections describe the results obtained from tests run on the two different BCB resin systems. Unless otherwise noted all tests have been run as specified above. 

Analytical Techniques. The cloud point of the blends was determined with a light-transmission device (21). Once the blend was cloudy, the test tube was taken out and chilled in ice, so that the time and conversion at the cloud point, tc and a could be obtained. The Tg value and conversion were measured by DSC (Mettfer TA3000 microcalorimeter) (22). The gel time, fge], of rubber-cyanate blends was determined as the time at which insolubles appeared in tetrahydrofu-ran (THF). That of PES-cyanate was determined by dynamic mechanical analysis (Rheometrics RDA700). 

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. 

Dynamic Mechanical Analysis. A Rheometrics Dynamic Mechanical Thermal Analyser (DMTA) Mk III was used in a single cantilever arrangement. Both and tan 5 were measured as a function of temperature at a frequency of IHz over the temperature range -145 to +150 C and a heating rate of 2 C/min for the isochronal experiments. 

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. ... 

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. 

DMA Measurements. Elastic tensile modulus, E of the standard polymers was measured by dynamic mechanical analysis, DMA, on a Rheometrics RSAII DMTA apparatus. Measurements were done at 1 Hz. The deformation amplitude was limited to 0.02% for the stiffer polymers and to 0.1% for the softer ones. 

Dynamic mechanical analysis (DMA) of the samples was performed on a Rheometric Scientific DMTA IV at a driving frequency of 10 Hz and a temperature scanning rate of 3"C/min. Tensile tests were performed at room temperature using dumbbell-shaped specimens on an Instron 1121 electronic testing machine at a crosshead speed of 20cm/min. An average value of five specimens was taken. 

The glass transition temperature and the temperature-dependent storage modulus (G ) can be measured particularly sensitive with the DMA (Dynamic Mechanical Analysis) in the torsion oscillation test. The evaluation of the glass transition temperature took place in accordance to the method of the half steps level . The measurements were performed at a Rheometric Scientific DMA MK III (-50°C-350 °C). 

Dynamic mechanical anlaysis (DMA) measurements were done on a Rheometrics RDS-7700 rheometer in torsional rectangular geometry mode using 60 x 12 x 3 mm samples at 0.05% strain and 1 Hz. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA) were performed on a Perkin-Elmer 7000 thermal analysis system. 

Detailed analysis of the isothermal dynamic mechanical data obtained as a function of frequency on the Rheometrics apparatus lends strong support to the tentative conclusions outlined above. It is important to note that heterophase (21) polymer systems are now known to be thermo-rheologically complex (22,23,24,25), resulting in the inapplicability of traditional time-temperature superposition (26) to isothermal sets of viscoelastic data limitations on the time or frequency range of the data may lead to the appearance of successful superposition in some ranges of temperature (25), but the approximate shift factors (26) thus obtained show clearly the transfer viscoelastic response... 

Because of their complex structure the mechanical behavior of polymeric materials is not well described by the classical constitutive equations Hooke s law (for elastic solids) or Newton s law (for viscous liquids). Polymeric materials are said to be viscoelastic inasmuch as they exhibit both viscous and elastic responses. This viscoelastic behavior has played a key role in the development of the understanding of polymer structure. Viscoelasticity is also important in the understanding of various measuring devices needed for rheometric measurements. In the fluid dynamics of polymeric liquids, viscoelasticity also plays a crucial role. " Also in the polymer-processing industry it is necessary to include the role of viscoelastic behavior in careful analysis and design. Finally there are important connections between viscoelasticity and flow birefringence. ... 

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