Calorimetry techniques

Strict control of the fusion process is imperative. In addition to thickness, hardness, continuity and adhesion checks, correct cure may be assessed by differential scanning calorimetry techniques, which are designed to measure any difference in the glass transition temperature of a laboratory-cured powder and the cured coating taken from the factory-coated pipe. 

This paper reviews recycling technologies of PMMA waste, its applications and its markets. It relates in detail experimentation on thermal and oxidative depolymerisation of PMMA scrap, under nitrogen and oxygen atmospheres, at different heating rates by thermogravimetry and differential scanning calorimetry techniques. 15 refs. 

Mixing calorimetry Technique used to measure heat evolved upon instantaneous mixing of two or more chemicals usually designed to be rapid (15 to 45 minutes), operating over the range of-50 to 200 degrees Celsius (°C). 

Solvation enthalpy data for neutral short-lived species, like radicals, are even more scant than for long-lived stable molecules. They can only be experimentally determined through indirect methods, namely, by comparing the enthalpies of reactions of those species in solution and in the gas phase. The former are obtained, for instance, by using the photoacoustic calorimetry technique (see chapter 13), and the latter by several gas-phase methods. 

The photoacoustic calorimetry technique employs photolysis by laser pulses of a mixture containing di-im-butyl peroxide, an appropriate metal hydride, and solvent. Photolysis of the peroxide gives i-BuO radicals that abstract a hydrogen atom from the hydride, and the measured photoacoustic signal is proportional to the overall reaction enthalpy. After calibration,... 

There are various methods to conduct a fragment screening campaign. The most commonly utilized methods include various NMR techniques, mass spectrometry, SPR, and biochemical screens. X-ray crystallization is a preferred method since it provides a binding conformation, but can only be used when the target protein is well behaved. Various calorimetry techniques have also been used for fragment screening, but these have been less commonly utilized. The merits of each method have been discussed in the literature (26) and will not be outlined here. 

The low-temperature properties of some of these peculiarly filled materials have also been studied by the calorimetry techniques mentioned in Chapter 2. Of particular interest is the way in which reinforcing particles can affect the crystallization of a polysiloxane, both in the undeformed state and at high elongations.45... 

Guillot A, Stoeckli F, and Bauguil Y. The microporosity of activated carbon fibre KF1500 assessed by combined C02 adsorption and calorimetry techniques and by immersion calorimetry. Adsorpt. Sci. Technol., 2000 18(1) 1-14. 

Ollivon, M., Loisel, C., Lopez, C., Lesieur, P., Artzner, F., Keller, G. 2001. Simultaneous examination of structural and thermal behaviours of fats by coupled X-ray diffraction and differential scanning calorimetry techniques application to cocoa butter polymorphism. In, Crystallization and Solidification Properties of Lipids (N. Widlak, R. Hartel, S. Narine, eds.), pp. 34-41, AOCS Press, Champaign, IL. 

A comparison between pulsed flow and conventional pulsed static calorimetry techniques for characterizing surface acidity using base probe molecule adsorption has been performed by Brown and coworkers [20, 21]. In a flow experiment, both reversible and irreversible probe adsorption occurring for each dose can be measured, and the composition of the gas flow gas can be easily modified. The AHads versus coverage profiles obtained from the two techniques were found to be comparable. The results were interpreted in terms of the extent to which NH3 adsorption on the catalyst surface is under thermodynamic control in the two methods. 

Nb(cr) and Nb(t) obtained from levitation calorimetry techniques. In the vicinity of the adopted enthalpy vlaues for Nb(cr)... 

Simultaneous Examination of Structural and Thermal Behaviors of Fats by Coupled X-ray Diffraction and Differential Scanning Calorimetry Techniques Application to Cocoa Butter Polymorphism... 

In a study of selective adsorption of sulfur compounds and aromatic compounds in a hexadecane on commercial zeolites, NaY, USy, HY, and 13X by adsorption at 55 °C and flow calorimetry techniques at 30 °C, Ng et al. found that a linear correlation between the heat of adsorption and the amount of S adsorbed for NaY.162 Competitive adsorption using a mixture of anthracene, DBT, and quinoline indicates that NaY selectively adsorbs quinoline, while anthracene and DBT have similar affinity to NaY, indicating that NaY is difficult to adsorptively separate sulfur compounds from aromatic hydrocarbons with the same number of the aromatic rings. 

Frolova et al. [84FRO/MEL] used a vacuum adiabatic calorimetry technique to measure the low temperature (5.7 to 313.6 K) specific heat of Zr(S04)2 4H20(cr). They... 

This is an investigation of the heat capacity of zirconium, titanium and zirconium alloys using an adiabatic calorimetry technique in the temperature range 60 lo 960°C. Two samples of zirconium were studied and nine separate experiments were accepted by the authors. However, all experiments exhibited a maximum in the heat capacity between 180 and 250 C, a feature which is inconsistent with previous or subsequent studies of the heat capacity or enthalpy of the metal, fhe position of the maximum varied from run to run. I lic author e.xplaincd the peak as being due to the presence of an amount of zirconium hydride in the sample and provided some evidence for the observed behaviour, demonstrating that as little as 0.26% hydrogen (28.5 ppm) could explain the results obtained. If this explanation was correct, each of the runs would contain a differing... 

This study presented data for the heat capacity of pure monoclinic zirconium dioxide and yttria-stabilised zirconium dioxide. The data were determined using the adiabatic calorimetry technique between 13 and 300 K. The purity of the zirconium dioxide used was 99.983%. There are no uncertainties reported in the study although the standard deviation in data from the experimental technique is reported as 0.3% at 50 K and 0.1% above 100 K. 

Various techniques have been developed in turn the Mooney viscometer, the Wallace-Shawbury curometer, the oscillating disc rheometer (ODR), and the moving disc rheometer (MDR), in addition to the calorimetry techniques. The isothermal calorimetry and its counterpart in scanning mode, the isothermal moving disc rheometer (MDR), and the improvement of this last technique with the rubber process analyzer run in scanning mode, are considered. 

In calorimetry techniques, enthalpy changes accompanying physical or chemical events, whether they are exothermic or endothermic, are measured and monitored either as a function of temperature or time. Thus, a calorimeter is able to collect a heat flux exchanged between the sample and the sensible part of the apparatus, generally made of thermocouples, and to register it. The result is a profile of the rate of enthalpy change, either as a function of temperature as the sample is heated at a known linear rate in differential scanning calorimetry (DSC), or as a function of time when the calorimeter is held at constant temperatnre in isothermal differential calorimetry (DC). 

The calorimetry techniques have been used for many purposes in the cure of rubber, including to measure the heat of the overall cure reaction, but also for evaluating the kinetics of the heat evolved from the overall reaction. The only question at first was what way to use the calorimetry In the early eighties, it seemed to a majority of the authors that the isothermal condition would be preferable, but finally the operation in scanning mode was preferred. 

Finally, the history has been similar both with the MDR or the calorimeter. After being utilized under isothermal conditions a few decades ago, the calorimetry technique is now widely used in the scanning mode, and the MDR, quite recently, could be used in scanning mode with the rubber process analyzer. 

MetastabiUly - a common feature in both macromolecular and pharmaceutical systems - is a second major challenge for the coming years. For a thorough understanding of die kinetics of all lands of temperature- and time-dependent processes related to metastability, there is now an urgent need for new and better-matching thermal analysis and calorimetry techniques. 

Metals as a class of materials are limited in the thermal analysis and calorimetric techniques that can be used for quality control purposes. Some high temperature DTA work can be done, but DSC, DEA, DMA, and most calorimetry techniques are not found in quality control labs working with metals, but there are some alternative approaches. Because metals are usually formed at very high temperatures, there is little to be done once the metal is formed and cooled. However, there are some interesting techniques that are used to study the influences of the cooling process on the formation of the various phases of the metal in a product. 

The receptor cavity of calix [njarenes favors the formation of complexes with amines by proton transfer. NMR spectrometry and calorimetry techniques allowed for the evaluation of the role of the cavity and the phenolic oxygens in the case of calix[4]arene complexes with aliphatic amines. Hydrophobicity and bas strength are important, and thus, the order of binding is tert-butyl-... 

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