Rheometric dynamic scanning

Analytical techniques, such as rheometric dynamic scanning and differential scanning calorimetry, that give information on changes in viscosity and the amount of heat absorbed or liberated during cure... 

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. 

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. 

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. 

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. 

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 Spectroscopy. Samples were run in the tensile mode using a Rheometrics Model 605 Mechanical Spectrometer. Temperature scans were run from -160 to 240 C using a strain of 0.15% and a frequency of 1 Hertz. Samples were maintained in a nitrogen atmosphere during testing. 

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. 

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 (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. 

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