Thermal mechanical analysis test

Thermal-mechanical analysis (TMA) has proven a more reproducible measure of melt integrity [20]. The TMA test involves measuring the shape change of a separator under load while the temperature is linearly increased. Typically, separators show some shrinkage, then start to elongate, and finally break (see Fig. 5). 

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

FFE-1, the blsphenol A/blsphenol fluorenone copolyester had a Tf (Indicative of glass transition) at 177 C. Polymer FPE-4 could not be molded into a Clash-Berg specimen. Therefore, a filter paper was coated by THF solution of sample FPE-4 and dried. Eight strips were compiled and made into one test specimen and the Clash-Berg test was run. A Tg of 270 C is indicated (Figure 9). This is the same value as that determined by thermal mechanical analysis. 

Dynamic mechanical thermal analysis measures damping and dynamic moduli and is covered in Chapter 21. Thermal mechanical analysis measures deformation of a test piece. such as the dimensional change due to thermal expansion (also called thermodilatometry) and indentation at the softening point of the material. 

Thermal mechanical analysis affords a method of obtaining precision results on a small test piece as a function of temperature. A procedure for plastics using DMA is given in a draft ISO standard, ISO DIS 11359-2 [9]. 

Ramamurthy and his colleagues [29] investigated the influence of addition of MWNTs to PANi Aims fabricated by solution processing. The physical characterization of these composites by tensile testing and dynamic thermal mechanical analysis indicated that PANi containing 1% w/w MWNTs is more mechanically and thermally stable than PAni itself. However, only marginal improvements in mechanical properties were reported. 

Dynamic Mechanical Analysis (qv) (DMA) or dynamic thermal mechanical analysis (DTMA) indicate damage in polymers or PMC (34), and aging effects in polymers by a shift in the transition temperature (35). Limitations are the volume of the test chamber or the required specimen shape. 

With a direct measurement of cooperativity of the thin films via dielectric spectroscopy not attainable, attention was turned to probing the system indirectly. As discussed previously, changes in the glass transition temperature can indicate changing cooperativity. Thermal mechanical analysis (TMA) was used to survey the Tg of the system. Due to the favorable interactions of the PMMA side chains and the native oxide layer of silicon, the thinner films were expected to increase in cooperativity and therefore show an increase in Tg. The tests were started with the thickest films, 900 nm. 

Thermal mechanical analysis (TMA) was performed on a TA 2940 thermal mechanical analyzer to measure the glass transition tempanture and thermal expansion coefficients. The heating rate was 5 IC/min. For each sample, three specimens wo-e tested. 

An appropriate cure cycle was established based on the results obtained from the thermal analysis and cure rheology studies of the resin and cured BCB bar and dogbone shaped samples were fabricated for testing. Bar shaped specimens had the dimensions of 3.5 x 0.5 X 0.125 and were used to stake compact tension specimens for fracture toughness studies and for dynamic mechanical analysis of a torsion bar. Dogbone shaped specimens for tensile tests had a gauge area of 1 x 0.15 and were approximately 0.040 thick. 

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. 

Under suitable simplifying assumptions, a kinetic mechanism based on 13 components and 89 second-order reactions is developed. The relevant kinetic parameters (preexponential factors, activation energies, and heats of reaction) are computed on the basis of literature information. In the subsequent chapters, this kinetic model is used to test the techniques for identification, thermal stability analysis, control, and diagnosis of faults presented. 

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. 

The small sample size, rapid removal of pyrolysis or combustion products, and availability of huge excesses of reactant oxygen during thermal analysis can lead to erroneous interpretation of the material in terms of its performance in actual thermal situations. However, thermal analysis tests can provide basic information on the pyrolysis and combustion mechanism and can provide data on the relative performance of materials. This information should be supported by larger-scale fire tests. 

While TMA is one of the older and simpler forms of thermal analysis, its importance is in no way diminished by its age. Advances in DSC technology and the appearance of dynamic mechanical analysis (DMA) as a common analytical tool have decreased the use of it for measuring glass transitions, but nothing else allows the measurement of CTE as readily as TMA. In addition, the ability to run standardized material test methods at elevated temperatures easily makes TMA a reasonable alternative to larger mechanical testers. As the electronic, biomedical, and aerospace industries continue to push the operating limits of polymers and their composites, this information will become even more important. During the last 5 years a major renewed interest in dilatometry and volumetric expansion has been seen. Other thermomechanical techniques will also likely be developed or modernized as new problems arise. 

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