TMA Equipment

The sample holder is generally made of quartz or steel. A sample is placed on the holder and the selected probe is placed in contact with the sample surface. A measured load is applied and the temperature program started. As the sample expands, softens, or contracts, the position of the probe changes. The position change is measured by the LVDT, which provides a voltage proportional to the deflection of the probe. 

Loads of 0.1-200 g or forces of 0.1-100 N may be selected and furnace temperatures may be programmed from -150°C to 1000°C, depending on the particular instrument. Samples of various sizes and shapes may be measured lengths of 1 pm-50 mm are common, with diameters in the 10 mm range, depending on the particular probe and instrument design. 

TMA instruments must be calibrated for both temperature and dimensional motion. The temperature is calibrated using the same type of melting point standards used for DSC. High-purity In, 

and A1 are often used. The LVDT is calibrated by using a standard with a well-known linear CTE, such as Al. The initial length of the standard is determined at room temperature and then the change in length of the standard with temperature is measured. The linear CTE, a, is defined by 

The calculated value of a is compared to the literature value for the material and a correction factor is applied to the data if needed. 

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Thermomechanical Analysis (TMA). Thermomechanical analysis (TMA) measures shape stability of a material at elevated temperatures by physically penetrating it with a metal rod. A schematic diagram of TMA equipment is shown in Fig. 2.23. In TMA, the test specimen s temperature is raised at a constant rate, the sample is placed inside the measuring device, and a rod with a specified weight is placed on top of it. To allow for measurements at low temperatures, the sample, oven, and rod can be cooled with liquid nitrogen. 

Sample preparation will depend on the glass to be measured and the TMA to be used. In typical TMA equipment, the sample space is of about 10 mm diameter. In order to allow for the sample to be pressed out during the measurement, the maximum sample diameter at the start will be about 5 mm. Sample height is not critical but should be less than the... 

In liquid-liquid systems effects of surfactants are again quite complex they serve to reduce circulation and depress interfacial turbulence, promote emulsification, aed provide en additional burrier to mass tmas-fer. ioo.ios present any particular system of interest should be investigated specifically. In practice, the effects are difficoli to isolate because of the low concentration levels of coniaminants that are effective and die maliy sources of contamination available in processing equipment. 

The table below lists the various TA techniques following the notation of the ICTA (International Committee for Thermal Analysis) nomenclature committee. The three "classic" TA techniques are DSC, TGA and TMA of which DSC is still the "workhorse". TA is also covering, however, a substantial number of other techniques and applications and several of these techniques are described in this book. This book is not a comprehensive textbook about TA but more a survey of the author s work during many years, at the Koninklijke Shell Laboratorium in Amsterdam. It describes in six chapters the use of the various TA techniques (printed in bold in the table) for specific problems, illustrating the versatility of TA. A technical description is only given for equipment of own design. 

The automated systems have a broad price range, depending on the degree of automation. In addition, some laboratories have had local initiatives to develop automated TMA construction (19). As is expected, the equipment needed for the manual method is the least expensive Fig. 3 shows a manual TMA machine. It is important for the laboratory embarking on an investment in this area to evaluate the machines. Each machine is different with different capabilities designed to... 

The measured quantity can be weight loss (TGA), a mechanical quantity (TMA) or a comparison between the behavior of two specimens (DTA) which, when properly calibrated, yields thermodynamic quantities that compare favorably with older, more conventional calorimetric techniques. Since the measurement time and equipment costs for scanning calorimetry (DSC) are orders of magnitude lower, the DSC has essentially replaced the conventional adiabatic calorimeter and finds a place in nearly every modern analytical laboratory. 

Phenaz-TMA/AuNPs on DNA and theLPR color changes involved. Furthermore, it was possible to create 2D patterns of metallic nanoarrays by the TP technique. Our methods summarized here do not require any special equipments, and should provide a useful system for investigating the electromagnetic (light) field localized between MNPs. 

Since the equipment to measure the temperature-induced dimension variation employs an LVDT displacement sensor, the requirement of a solid sample is mandatory. The effects of post-cure reaction on the measurement, instead, need much more detail and discussion. For a partially cured thermosetting resin, a post-cure reaction is expected when the actual temperature rises above the corresponding glass-transition temperature, Tg. Above this temperature, the volume variation due to post-cure reactions is superimposed upon thermal expansion (18). For this reason, TMA is a technique for measuring the CTE of the partially cured sample that is suitable only within the glassy region (T < Tg), while for a fiilly cured sample useful information can also be obtained for the CTE in the rubbery... 

Thermomechanical Analysis. The equipment used in thermomechanical analysis (TMA) is similar in principle to that for TD, but provision is made for applying various types of load to the specimen, so that penetration, extension, and flexure can be measured. This approach to analyzing such modes of deformation is illustrated schematically in Figure 15. The technique finds most use in polymer studies, as in the determination of glass-transition and softening temperatures for thin films and shrinkage characteristics of fibers. 

Fig. 1 Alkyd resin processing equipment. [Reprinted from Amoco TMA as Primers for Alkyd-Melamine Enamels and Acrylic Lacquers, Tec. Bull. TMA 25a. Amoco Chemical Corp., Chicago, Illinois, 1974.]...

MAO prepared by the use of CuS04 5H20 contains small amounts of copper compounds. To produce a pure MAO and to prevent any side reactions it is necessary to use TMA and water or ice only. This allows the calculation of mass-balances and a better characterization. The research group of Sinn used an ice-plate that was washed with a stream of a TMA solution [32]. The reaction takes place at the surface only, forming a white film. This film is dissolved if the stream of the solution on the top of the plate exceeds turbulence. A rotating scraper was used in such a way that it did not erode the ice. A detailed description of the equipment can be found in [33]. 

Ari DIDC Monomers Preparation and Properties. The general procedure is detailed for 2,6 TDA-DIDC. The following components were placed in a 500 ml 3-neck round bottom flask equipped with N2 purge, mechanical stirrer and a dean-stark trap TMA (25.0556 g 0.13 moles) DMF (75 ml). The mixture was heated to 60°C for 1 hour to dissolve the TMA. Then 2,6TDA (7.941 Ig 0.065M), DMF (25 ml) and mXylene (20 ml) were added to the reaction mixture and the dean-stark trap was filled with mXylene. The temperature was raised to 190°C and water (2.5-3.0 ml)... 

The morphology of the composites were carefully analyzed by WAXS and TEM for the montmorillonite and AFM for the elastomer-dispersed phase. The additional mechanical property that was measured in this work was the CTE with the same equipment, TMA 7, and protocol that was employed in the second article in this series (see above). 

The coefficient of thermal expansion (CTE) can be measured through several methods, the most direct being through linear or volumetric dilatometry. Thermal mechanical analyzers (TMAs) are ideally suited for such measurements, as their components are made of very low expansion materials such as quartz. With precise temperature control, they are able to accurately measure linear dimensional changes as a function of temperature. They are often equipped to measure other properties such as softening temperature in addition to the coefficient of thermal expansion as a function of temperature. 

We measured the coefficient of thermal expansion, CTE, of RX-55-AE-5 using a TA Instruments Model 2940 TMA that was controlled by a TA 500 Thermal Analyzer equipped with a TMA Mechanical Cooling Accessory [6,7]. A quartz micro-expansion probe sat on top of all samples with a force of 0.01 Newtons (N). The change in the length of the sample was as it was heated or cooled was measured by a linear transformer that converted the vertical distance of the quartz motion probe and was recorded by the TA Instrument software. Ultra high purity nitrogen carrier gas was used at a constant flow rate of 100 cm /min. Samples were heated at a linear heating rate of 3°C /min. 

A practical distinction between TMA and TDA is simply that in TMA some kind of stress or load is applied to the test material, while in TDA no load or stress is required. The same basic equipment may be used. In commercial equipment the temperature may go as low as -170°C or as high as 1000°C. 

A wide variety of equipment is available, which includes the measurement of various properties. The list given here, with brief descriptions, is illustrative rather than comprehensive. Logically volume changes and measurement of density should be discussed under this heading. However, most commercial TMA units note only a single dimensional change on fabricated units (it is difficult to make TMA measurements on powders). The measurement of density involves techniques which would be difficult to... 

Thermomechanical analysis (TMA) predates the use of dynamic mechanical analysis techniques. TMA is used for 7 determination, but is significantly less sensitive than DMA and cannot be used for studying the weaker p relaxations, as seen in many polymers. In many respects TMA is the simplest form of thermal analysis equipment. A small sample is mounted in the instrument, which is surrounded by a furnace and the variation of sample length is recorded as a function of time or temperature. 

In plastics analysis, there are a variety of analytical methods for characterization of morphological differences related to degradation of resins from reprocessing. These techniques include FTIR, thermal analysis (TGA, DSC, TMA, DMA), Colorimetric analysis, ESCA or XPS, and GPC. These methods can be laborious and require technical expertise and equipment not always readily available. An imaging method correlated to one of these techniques, especially Melt Flow Index, is extremely useful. Such a method is rapid to obtain by imaging, reduces sample preparation time, and provides a scale of intensities for purposes of correlation. The method is surface sensitive. 

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