Dynamic thermal analysis

A technique is described [228] for solving a set of dynamic material/energy balances every few seconds in real time through the use of a minicomputer. This dynamic thermal analysis technique is particular useful in batch and semi-batch operations. The extent of the chemical reaction is monitored along with the measurement of heat transfer data versus time, which can be particularly useful in reactions such as polymerizations, where there is a significant change in viscosity of the reaction mixture with time. 

Other thermal techniques are Thermogravimetric Analysis (TGA) [55,68], High Pressure Calorimeter (HPC) [1], Thermomechanical Analysis (TMA) [1,141], and Differential (or Dynamic) Thermal Analysis (DTA) [74]. These are rarely used and will not be discussed here. 

Equation (9.19) is the most basic equation for the dynamic thermal analysis of an SOFC cell/stack. As one would expect, the equation shows that under steady state, the change in enthalpy from inlet to exit is equal to the internal heat generation within the system. 

Salhab M, Keith LG, Laguens M et al (2006) The potential role of dynamic thermal analysis in breast cancer detection. Int Semin Sing Oncol 3 8... 

Dynamic thermal analysis confirm these findings, where the epoxy diacrylate material begins to oxidize at a considerably lower temperature than the urethane diacrylate (Table II). The instability of the epoxy diacrylate is also confirmed by UV spectra of films heated in oxygen to 200 "C on quartz plates (Figure 2). Absorptions at 282 and 278 nm in the initial spectrum are... 

However, to use thermodynamically calculated results for the interpretation requires the consideration of the materials microstructure, specific crystallization behavior and the kinetics of phase formation and phase reaction. This is true especially for the interpretation of dynamic thermal analysis experiments (e.g. DTA, TG). Moreover, heat treatments (e.g. thermolysis) are often carried out in an inert atmosphere and evaporating gaseous species are continuously removed by flowing gas atmospheres (inert or reactive). This effect deeply... 

J. Chiu, Dynamic thermal analysis of polymers, an overview, J. Macromol. Sci. Chem.) A8, 1 (1974). 

NONEQUILIBRIUM THERMODYNAMICS AND MODERN DYNAMIC THERMAL ANALYSIS TECHNIQUES... 

DMTA Dynamic Thermal Analysis of Mechanical Properties... 

Irgashi and Kambe [3] also studied the thermal degradation of polyethylene and used dynamic thermal analysis (DTA) as well as TGA techniques. The experiments were carried out in both air and nitrogen. The PE studied were, two low-density samples. By means of DTA, the crystallinities of the high-pressure samples were found to be 33% and 36% while those for the low-pressure samples were 64% and 77%, and the melting points of the latter samples were higher than those of the former. 

TGA, dynamic thermal analysis (DTA) and infrared (IR) techniques have been used [11-13] to determine E and n of BPA and resorcinol based epoxies. Figure 3.3 shows the TGA derived curves for BPA and resorcinol-based epoxy resins. The replacement of the phenyl group between two glycidyl ether groups in resorcinol diglycidyl ether by a 2,2-diphenylpropyl group increased appreciably the maximum decomposition rate. 

The papers presented in the following chapters represent advances in pressure sensitive adhesives (ultraviolet light activated acrylate monomer - low Tg polyether formulations) photoinitiated cationic polymerization (light activated aryliodonium and arylsulfonium salts of lewis acids in epoxy resin formulations) polymer and formulation design criteria for radiation curable adhesives radiation curable composites (dynamic thermal analysis characterization of electron beam cured... 

Dynamic Thermal Analysis Characterizations of Electron-Beam Cured Adhesives... 

Thermogravimetric Analysis A dynamic thermal analysis technique in which the weight loss of a sample is measured continuously while its temperature is increased at a constant rate. 

Schwartz and co-workers [97] used isothermal differential thermal analysis to study the diffusion of Irganox 1330 (1,3,5 tris (3,5 di-tor -butyl-4-hydroxyl benzyl) mesitylene) in extruded sheets of isotactic polypropylene (iPP). Studies were conducted over the temperature range 80-120 °C. The measurements showed a clear relation between oxidation induction time and oxidation maximum time [both determined by isothermal dynamic thermal analysis (DTA)] and the concentration of stabiliser. It was possible to calculate the diffusion coefficients and the activation energy of diffusion of Irganox 1330 in iPP by measuring the oxidation maximum times across stacks of iPP sheets. 

DMA provides material scientists and engineers with the information necessary to predict the performance of a material over a wide range of conditions. Test variables include temperature, time, stress, strain, and deformation frequency. Because of the rapid growth in the use of engineering plastics and the need to monitor their performance and consistency, dynamic thermal analysis has become the fastest growing thermal analysis technique. 

Table 3.8 Frequency dependence of transition and relaxation temperatures from dynamic thermal analysis ...

Figure 2.9 shows results of a long-term tensile test at 120 °C versus failure times obtained by long-term dynamic thermal analysis for iPP with different Irganox 1330 concentrations between 0 and 0.03 w w%. The beginning of the abrupt decrease in tensile strength is coincident with the oxidation maximum time. 

Anderson and Ereeman [11] studied the thermal properties of a styrenated polyester synthesised by condensation involving a glycol and two dicarboxylic acids, one of which was unsaturated. A crosslinking reaction of the styrene (used as a solvent and copolymer) was effected by the use of free-radical initiators. TGA, dynamic thermal analysis, IR and mass spectrometric techniques were used to study the thermal degradation of this polymer in air and in argon. Based upon IR analysis, the unit basic structure of the polyester was taken to be as in Equation 3.18 ... 

Dan and co-workers [8] studied the structures and thermal and thermo-oxidative stabilities of the gel and chlorinated natural rubber from latex. The polymers were analysed by chemical analysis, high-resolution pyrolysis-gas chromatography-mass spectroscopy (HR-Py-GC-MS) coupled with Fourier-transform infrared spectroscopy, and thermal analysis techniques [dynamic thermal analysis and thermogravimetric analysis (TGA)]. 

Brinson, H. F., Dickie, R. A., and Debolt, M. A., Measurement of Adhesive Bond Properties Inclnding Damage by Dynamic Thermal Analysis of a Beam Specimen, J. Adhesion, 55 17-30 (1995)... 

Dynamic Mechanical Thermal Analysis (Dynamic Thermal Analysis) DMTA DMA Response to Oscillatory Load... 

Choi et al. reported the preparation of CdS and polyacrylonitrile (PAN)-CdS nanocomposites by y-irradiation polymerization." The prepared CdS and PAN-CdS nanocomposites were characterized by powder XRD, IR spectroscopy, Fourier transform (FT) Raman spectroscopy, TEM, X-ray photoelectron spectroscopy (XPS) and TGA (thermogravimetric analysis/dynamic thermal analysis). In photoluminescence (PL) spectroscopic analysis, the maximum peak of PAN-CdS nanocomposites prepared by y-irradiation polymerization was at about 485 nm, whereas the maximum peak of CdS nanocomposites was at about 460 nm. 

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