Mechanical thermal analysis

Thermal mechanical analysis can be used to assess the glass transition of a thin film system. The sample is placed in a temperature-controlled chamber for analysis. Two different probes can be used with thermal mechanical analysis (TMA) a flat probe or a penetration probe. The flat probe measures the thermal expansion of the polymer as the temperature is increased. Very little load is applied, so an accurate measure of change in dimension can be reported. Conversely, the penetration probe can have up to 1.0 N of force placed on the sample. The probe pushes into the sample as it softens to give a crude modulus (or compliance) value or a temperature associated with a 

For bulk polymers, both the coefficient of thermal expansion and the modulus have been measured as mentioned above.A more sensitive procedure has been developed for thin film analysis called local thermal analysis (LTA). In this technique the probe itself is heated and is therefore able to measure the expansion and transitions of thin films more accurately. 

The glass transition temperature of ice cream can be measured by thermal mechanical analysis. A sample of unaerated frozen ice cream mix approximately 0.5 mm thick and 1 cm in diameter is placed between two plates. One of the plates is attached to a probe that measures the expansion of the sample as it is warmed up from below the glass transition temperature. Unaerated samples are used because aeration affects the thermal expansion. However, since the glass transition temperature is a property of the composition of the matrix, the absence of air does not affect the result. The glass transition temperature is indicated by a change in the rate of expansion that occurs at about — 30 °C for a typical ice cream. 

The meltdown test (or melt resistance) of ice cream measures its ability to resist melting when exposed to warm temperatures for a 

TMA is a method for measuring linear or volumetric changes in polymers as a function of temperature, time or force and is often used in conjimction with DSC to investigate the structure and properties of polymers. This combination is often found in commercial microthermal analysers (see Section 6.4.9). While the DSC is concerned with the energetics of physical and chemical changes, TMA measures the dimensional effects associated with these changes and so it can be used to obtain the coefficient of thermal expansion for polymer samples. 

TMA can also measure properties such as Tg and Tm polymers and is similar to DMA in this regard. 

DSC measures the heat flow into or out of a material as a function of time or temperature. What is being measured during a DSC experiment on a polymer sample is changes to its heat capacity (Cp) as a result of either endothermic or exothermic events. Examples of events that bring about the two types of changes are shown below  

A summary of the polymer-related applications that DSC can be used for is given below  

Identification of crystalhne polymers and polymer blends by their melting points. 

TMA results may indirecfly provide information about the spatial orientation of MMT layers in nanocomposite materials. 

A trend of CTE similar to the latter results was obtained by TMA measurements performed on the MWCNTs infused through and between glass fiber tows along the through-thickness direction [74]. Both pristine and functionalized MWNTs were used in fabricating multiscale glass fiber-reinforced epoxy composites. The CTEs of the resin and the resin-fiber system were tested by TMA with a ramp rate of 5 °C/min. 

TMA can also be used to measure Tg, in terms of change in the CTEs, as the polymer turns from glass to rubber state with a dramatic change in free molecular 

that is, polymer composites reinforced with inorganic fillers of dimensions in the nanometer range, have attracted great attention of researchers, due to unexpected synergistic properties derived from the two components. 

the efficiency of intercalation of the polymer in the lamellar galleries is usually measured by means of XRD and/or TEM. Although the wide-angle XRD offers a convenient method to determine the interlayer spacing of the silicate layers in the intercalated nanocomposites, little can be said about the spatial distribution of the silicate layers or on structural nonhomogeneities in nanocomposites. On the other hand, TEM is very time intensive, and only gives qualitative information on the sample as a whole, due to the small investigable area. 

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Thermal stability Hot electrical resistivity, thermal-mechanical analysis ... 

Figure 5. Thermal-mechanical analysis of Celgard microporous membranes.

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). 

BY DIFFERENTIAL THERMAL ANALYSIS OR DIFFERENTIAL SCANNING CALORIMETRY. fBY THERMAL MECHANICAL ANALYSIS EXCEPT WHERE NOTED. 

Thermally stimulated creep (TSCr) method, 21 742-743 Thermally stimulated current spectrometry (TSC), 21 743 Thermal mass meters, 20 681 Thermal mechanical analysis (TMA), of polyester fibers, 20 21 Thermal motion, in silicon-based semiconductors, 22 237-238 Thermal noise, silicon-based semiconductors and, 22 237 Thermal oxidation, 10 77-78, 79 in VOC control, 20 683-685 Thermal oxidation rates, silicon, 22 490 Thermal oxidizers... 

Characterization. Differential scanning calorimetry and thermal mechanical analysis data were obtained on a DuPont 990 thermal analyzer coupled with a DuPont DSC or TMA cell. Isothermal aging studies were carried out with an automatic multisample apparatus. 

Some zeolites such as AIPO4-5 (API) have a negative coefficient of thermal expansion over certain temperature ranges [230, 231]. For a zeolite formed into a pellet, one method to verify the presence of a negative coefficient of thermal expansion is by thermal mechanical analysis (TMA). For just the zeolite, powder X-ray diffraction at various temperatures can be used. Such an analysis can be of importance for identifying pellet strength or vessel containment issues. 

Major methods involved with the generation of information about thermal property behavior of materials include thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), differential thermal analysis (DTA), torsional braid analysis (TBA), thermal mechanical analysis (TMA), and pyrolysis gas chromatography (PGC). 

The glass transition temperature can be measured in a variety of ways (DSC, dynamic mechanical analysis, thermal mechanical analysis), not all of which yield the same value [3,8,9,24,29], This results from the kinetic, rather than thermodynamic, nature of the transition [40,41], Tg depends on the heating rate of the experiment and the thermal history of the specimen [3,8,9], Also, any molecular parameter affecting chain mobility effects the T% [3,8], Table 16.2 provides a summary of molecular parameters that influence the T. From the point of view of DSC measurements, an increase in heat capacity occurs at Tg due to the onset of these additional molecular motions, which shows up as an endothermic response with a shift in the baseline [9,24]. 

Figure 14.8. Thermal mechanical analysis (TMA) curve of 10FEDA/4FMPD film cured at 350°C...

Compatibilizer ABS copolymers have been prepared via an emulsion polymerization process. These copolymers have been functionalized with glycidyl methacrylate (GMA). The functionalized copolymers are blended PBT. Characterization by thermal mechanical analysis indicates that PBT is partially miscible with ABS and the glycidyl grafted ABS (48). 

Williams, N.A., Gugliemo, J. Thermal mechanical analysis of frozen solutions of mannitol and some related stereoiso-meres evidence of expansion during warming and correlation with vial breakage during lyophilization. PDA J. Parenteral Sd. Technol. 47,119-123, 1993... 

Thermal Mechanical Analysis and Dynamic Mechanical Thermal... 

General Experimental Protocols. As noted above, thermal mechanical analysis may be conducted in three separate modes standard, temperature-modulated, and force-modulated. Sample preparation requires dimensional stability, typically including either placement of the sample into a receptacle (useful for powders) or pressing into pellets or tablets. 

Figure 18.24. Thermal mechanical analysis scan of Leonardite humic acid at a heating rate of 2.5 °C min-1.

Figure 18.25. Thermal mechanical analysis scans of Nordic aquatic fulvic acid (NAFA) and Nordic aquatic humic acid (NAHA) indicating transitions near 18 °C and 23 °C, respectively, associated with the collapse of the structures following thermal transitions. Reproduced from DeLapp and LeBoeuf (2004), by permission of the Soil Science Society of America.

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