Dynamic mechanical thermal analyzer DMTA

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

The dynamic mechanical properties were studied via a Polymer Laboratories Dynamic Mechanical Thermal Analyzer (DMTA) used with ... 

The dynamic mechanical thermal analyzer (DMTA) is an important tool for studying the structure-property relationships in polymer nanocomposites. DMTA essentially probes the relaxations in polymers, thereby providing a method to understand the mechanical behavior and the molecular structure of these materials under various conditions of stress and temperature. The dynamics of polymer chain relaxation or molecular mobility of polymer main chains and side chains is one of the factors that determine the viscoelastic properties of polymeric macromolecules. The temperature dependence of molecular mobility is characterized by different transitions in which a certain mode of chain motion occurs. A reduction of the tan 8 peak height, a shift of the peak position to higher temperatures, an extra hump or peak in the tan 8 curve above the glass transition temperature (Tg), and a relatively high value of the storage modulus often are reported in support of the dispersion process of the layered silicate. 

The variation of the damping factor (tan 5) with temperature was measured using a Polymer Laboratories Dynamic Mechanical Thermal Analyzer (DMTA). The measurements were performed on the siloxanfe-modified epoxies over a temperature range of — 150° to 200 °C at a heating rate of 5 °C per minute and a frequency of 1 Hz. The sample dimensions were the same as those used for flexural modulus test specimens. 

Recently, Hon and San Luis [23] studied the thermal properties of cyanoethylated wood by DSC and dynamic mechanical thermal analyzer (DMTA). Depending upon the N content, the cyanoethylated wood exhibited a softening temperature ranging from 162°C to 177°C and melting temperature ranging from 240°C to 270 C. The DMTA measurements suggest that wood materials are susceptible to degradation upon cyanoethylation. 

BENDING OF A BEAM. The complex dynamic Young s modulus can be determined from the forced, non-resonant oscillations of a single or double cantilever beam. The apparatus considered in this paper is the Dynamic Mechanical Thermal Analyzer (DMTA) (6), manufactured by Polymer Laboratories, Inc. Figure 3 shows the experimental setup for the single cantilever measurement. A thin sample is clamped at both ends. One end is attached to a calibrated shaker through a drive shaft. 

Figure 3. Dynamic mechanical thermal analyzer (DMTA) apparatus.

The dynamic mechanical property data for Groups 1,2,and 3 materials were obtained from a Polymer Laboratory Model 983 Dynamic Mechanical Thermal Analyzer (DMTA), and include log tan S (loss factor), log E (storage modulus), and log E (loss modulus). Frequency was held constant at 10 Hz for all samples. The superposed results are shown for each group in Figures 2-10. 

Glass transition temperature, Tg, and storage modulus, E , were measured to explore how the pigment dispersion affects the material (i.e. cross-link density) and mechanical properties. Both Tg and E were determined from dynamic mechanical analysis method using a dynamic mechanical thermal analyzer (DMTA, TA Instruments RSA III) equipped with transient testing capability. A minimum of 3 to 4 specimens were analyzed from each sample. The estimated uncertainties of data are one-standard deviation. 

Dynamic mechanical properties were determined with a Polymer Laboratories Dynamic Mechanical Thermal Analyzer (DMTA) using the tensile mode. The fiber length was in all cases 20 mm at an initial 0.5% elongation. The heating rate was set to 5°C/min. Break tenacities were measured on an Instron tensile tester model 1130 using a sample length of 25.4 mm and a strain rate of 0.508 mm/min (0.02 in./min). All reported break-tenacities and moduli are the mean values of four measurements. 

There is a growing tendency to incorporate nanofillers into polymer blends. When the two polymers differ significantly in rigidity, their behavior resembles that of TPE. For example, a blend of PA-6 with PP (PA-6/PP = 70/30) compatibilized with EPR-MA was melt-compounded with 4 phr of MMT-ODA [Chow et al., 2005]. The CPNC had a high degree of clay dispersion and distribution. The dynamic mechanical thermal analyzer (DMTA) data (at 10 Hz) showed a tendency opposite to that observed for TPE The largest enhancement of E was obtained for non-compatibilized CPNC at the lowest temperature of -100°C (by about 25%) the addition of EPR-MA reduced this effect by one-half, up to - -100°C. However, for these systems the tensile moduli measured in steady state and dynamic mode at 23°C were comparable (i.e.. 

Thermal stability properties are measured by two complementary methods, i.e. tensile-type measurements at elevated temperatures using a hot-air environmental chamber and also the Dynamic Mechanical Thermal Analyzer (DMTA) method. In the DMT A test a small rectangular strip (40 mm X 10 mm x 2 mm) is subjected to constant cyclic deformation over a changing temperature range and the storage modulus ( ) recorded and used to relate change of stiffness with temperature. 

Dynamic mechanical spectra were obtained with a Rheovibron Model DDV II-C at 110 Hz and the Dynamic Mechanical Thermal Analyzer (DMTA) manufactured by Polymer Laboratories, England at 1Hz. The approximate heating rate for the sample was maintained near 3°C per minute in the Rheovibron and 5°C per minute for the DMTA. 

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. 

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...

---