TMA and DMA

DMA provides materials scientists, pol5mer chemists, and design engineers with detailed information on the elastic and inelastic (plastic) deformation of materials, modulus, and damping (energy dissipation) properties of materials. The damping behavior of S5mthetic and natural mbbers is important in vibration and acoustic application, for example. 

The mechanical modulus can be measured under different types of load-shear, flexure, and so on. The measured modulus can be expressed as the storage modulus (related to the 

Thermometric methods of analysis have wide analytical applications. They can be used not only for the identification of chemical compounds, but also for the quantitative analysis of mixtures of compounds and for characterizing many types of engineering materials such as 

Introduction to Thermal Analysis Techniques and Applications Chapman and Hall New York, 1988. 

Callister, W.D. Materials Science and Engineering An Introduction, 5th ed. John Wiley and Sons New York, 2000. 

Storage modulus Loss modulus Storage/loss compliance tan delta ( ) 

Complex/dynamic viscosity Creep compliance Relaxation modulus Static/dynamic force Temperature 

Stress/strain Frequency Sample stiffness Displacement 

DMA provides materials scientists, polymer chemists, and design engineers with detailed information on the elastic and inelastic (plastic) deformation of materials, modulus, and damping 

The mechanical modulus can be measured under different types of load shear, flexure, and so on. The measured modulus can be expressed as the storage modulus (related to the stiffness of the material) and the loss modulus (related to the viscous behavior or softness of the material) under the various types of loads. DMA is used to follow the curing of polymers and cross-linking of polymers and to measure glass transition tanperatures. 

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Beside BAs, low-molecular-weight alkylamines, commonly used as indicators of food quality, can also be present in fish muscle. Tri- and dimethylamine (TMA and DMA) are produced by bacterial reduction of the osmoregulatory substance trimethylamine oxide (TMAO) in fresh marine fish and by enzymatic reduction in frozen storage of gadoid fish (cod, cusk, hake, pollack), with concurrent formation of formaldehyde. 

Technological Advances. TMA and DMA are both widely employed in the characterization of viscoelastic behavior of polymers, composites, and other materials. Notably, TMA and DMA are particularly useful in identifying glass transitions and other low energy-associated sub-glass transitions, which may not be easily... 

Potential as a Tool for Thermal Analysis of NOM. As mentioned above, TMA and DMA represent more sensitive thermal analytical techniques relative to... 

DSC and DTA. They can be used to confirm suspicious glass transitions revealed by DSC and most important, they can further quantify molecular mobility associated with sub-glass transitions. For example, DSC analysis of poly (ethylene 2,6-naphthalene dicarboxylate) (PEN) only revealed the presence of a glass transition around 112 °C (Hardy et al., 2001). DMA analysis of the same sample, however, revealed two secondary relaxations below this glass transition (Hardy et al., 2001). In the case of humic materials, it is not uncommon for DSC to fail to detect clear thermal transitions due to their heterogeneous nature, which contributes to overlap/ broadening or washout of thermal transitions. As such,TMA and DMA represent powerful, complementary tools to DSC. 

TMA and DMA are widely used to study the properties of polymers and other materials under various experimental conditions in the temperature range from —200 to approximately 850CC. The former usually gives limited information on viscoelastic responses as well as dimensional changes, whereas the latter is concerned with viscous responses. 

FIGURE 9.10 Derivatization of TMA and DMA. DMA and TMA were derivatized to form A,A-dimethyl-p-toluene sulfonamide and Af,A-dimethyl-2,2,2-trichloroethyl carbamate. These were isolated using gas chromatography and fragmented using electron impact ionization. 

The potential use of amine concentration as a criteria to assess freshness in finfish and shellfish has been discussed by many researchers. The volatile amines trimethylamine (TMA) and dimethylamine (DMA) have been widely used as indicator of heshness of marine fish (Castell et al, 1971). Tables X and XI give the concentration of TMA and DMA in herring and... 

Figure 16.34 Representative sample probe shapes for TMA and DMA measurements. (Courtesy of PerkinElmer, Inc. Shelton, CT, www.perkinelmer.com.)...

In a manner analogous to TMA and DMA, a specimen can be subjected to a constant or oscillating electric field rather than a mechanical stress during measurements. Dipoles in the material will attempt to orient with the electric field, while ions, often present as impurities, will move toward the electrode of opposite polarity. The resulting current flow is similar in nature to the deformation brought about by mechanical tests and represents a measure of the freedom of charge carriers to respond to the applied field. The specimen is usually presented as a thin film between two metal electrodes so as to form a parallel plate capacitor. Two types of test can be performed. 

In the TMA plot in Fig. 7 it is possible to note the interactive nature of the substrate on the curing of the PF adhesive. For example, the modulus of elasticity (MOE) increase curve shows two sections (and a two peak first derivative curve). This indicates formation of entanglement networks of the resin in wood which is not possible on noninteractive substrates such as glass as in Fig. 6. Of course DMA and TMA give equally good results when used on the same wood substrate [379,380]. The ABES technique is also linearly correlated with TMA and DMA results as has been demonstrated by the linear relationship that has been found for both MUF and tannin formaldehyde adhesives in the results of TMA and ABES [381]. 

The important bioanalytical technique of microcalorimetry has been added to Chapter 16, Thermal Analysis, and TMA and DMA have been greatly expanded, thanks to the excellent materials and invaluable assistance from TA Instruments. Optical thermal instrumentation is now covered with the assistance of Expert System Solutions, Italy. 

Glass Transition Temperature Tg (DSC, TMA, and DMA). The resin systems used in today s copper-clad laminates are almost all three-dimensionally cross-linked thermoset polymers. This means that the materials are manufactured (in a curing reaction) into a hard final product and cannot be remelted many times the way thermoplastic polymers can. In many cases, different resin systems are blended to create a material with specific properties. The functionality of the individual resins and their ratio in the blend define the properties of the thermoset.The degree of cure of the hardened thermoset resin system can be described by characteristics such as percent of uncured monomer and heat of final cure or by mechanical properties such as hardness, modulus, and yield stress. But one of the most commonly used characteristics to describe the degree of cure and cross-hnk density of a thermoset polymer is the glass transition temperature (Tg). 

Hassel [103] has compared DSC, TG, thermal evolution analysis, TMA and DMA in evaluating flame retardant textiles based on different polyester fibres. Also the thermoanalytical analysis (DSC, TGA) of a sisal reinforced flame retardant poly-ester/(DBDPO, Sb203) formulation has been described [104]. Larcey et al. [105] have reported use of a simultaneous TG-DSC system (STA) to investigate the suitability of using magnesium hydroxide as a flame retardant and smoke suppressant in PP formulations. 

Infrared spectroscopy and thermal methods - DSC, TGA, TMA, and DMA - add specific information on the physical and mechanical properties of polymeric adhesives. 

There are two main types of mechanical thermal analysis instruments, namely thermomechanical analysis and dynamic mechanical analysis, TMA and DMA respectively. The first is a simple technique that has been available for many years and simply records change of sample length as a function of changing temperature. Despite this simplicity it enables the measurement of phase transitions, glass transition temperature and coefficient of thermal expansion. It has the advantage of being simple to use and perhaps more importantly the interpretation of results is quite straightforward. 

Both the TMA and DMA apply force and measure the displacement that results from this stimulus. Most TMAs and DMAs currently in production use linear variable displacement transducers (LVDTs) to measure displacement. There is one exception, which is the TA Instruments 2980, or later variant Q800, which uses an optical displacement transducer instead. 

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