Experimental techniques differential scanning calorimetry

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. 

From the discussion presented of reactions in solids, it should be apparent that it is not practical in most cases to determine the concentration of some species during a kinetic study. In fact, it may be necessary to perform the analysis in a continuous way as the sample reacts with no separation necessary or even possible. Experimental methods that allow measurement of the progress of the reaction, especially as the temperature is increased, are particularly valuable. Two such techniques are thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). These techniques have become widely used to characterize solids, determine thermal stability, study phase changes, and so forth. Because they are so versatile in studies on solids, these techniques will be described briefly. 

To use equation 2.10 correctly, we need to know how the heat capacities vary in the experimental temperature range. However, these data are not always available. A perusal of the chemical literature (see appendix B) will show that information on the temperature dependence of heat capacities is much more abundant for gases than for liquids and solids and can be easily obtained from statistical mechanics calculations or from empirical methods [11]. For substances in condensed states, the lack of experimental values, even at a single temperature, is common. In such cases, either laboratory measurements, using techniques such as differential scanning calorimetry (chapter 12) or empirical estimates may be required. 

The enthalpies of phase transition, such as fusion (Aa,s/f), vaporization (AvapH), sublimation (Asut,//), and solution (As n//), are usually regarded as thermophysical properties, because they referto processes where no intramolecular bonds are cleaved or formed. As such, a detailed discussion of the experimental methods (or the estimation procedures) to determine them is outside the scope of the present book. Nevertheless, some of the techniques addressed in part II can be used for that purpose. For instance, differential scanning calorimetry is often applied to measure A us// and, less frequently, AmpH and AsubH. Many of the reported Asu, // data have been determined with Calvet microcalorimeters (see chapter 9) and from vapor pressure against temperature data obtained with Knudsen cells [35-38]. Reaction-solution calorimetry is the main source of AsinH values. All these auxiliary values are very important because they are frequently required to calculate gas-phase reaction enthalpies and to derive information on the strengths of chemical bonds (see chapter 5)—one of the main goals of molecular energetics. It is thus appropriate to make a brief review of the subject in this introduction. 

The aim of this contribution is to highlight new applications of calorimetric techniques to study soft matter organization directly on this length scale. Two original techniques, namely thermoporosimetry (TPM) and photo-differential scanning calorimetry (photoDSC) will be presented from both the theoretical and experimental points of view. After giving the state of the art of the two techniques,... 

Extensive work has been carried out to quantify the physical behaviour of the triglycerides. Five or six crystalline forms have been identified using experimental techniques such as observing crystals melting under a microscope, and more recently, differential scanning calorimetry (DSC) and X-ray diffraction (or a combination of those). 

The aromaticity has been studied by pressure differential scanning calorimetry (PDSC). The details of the experimental technique and of the methods for calculating aromaticity from a PDSC thermogram... 

Detection and characterization of polymorphs and/or solvates rely on various experimental techniques. X-ray powder diffraction (XRPD), solid state nuclear magnetic resonance (NMR), solid state infrared (IR) and solid state Raman are useful in demonstrating differences in the solid state. Thermal analytical techniques, including differential thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetry (TG), are also... 

Availability of direct experimental studies of thermochemistry of surface centers/adsorbates Limited technique—in situ differential scanning calorimetry Sinev and Bychkov (1999) ( + /-)... 

The most important experimental techniques in this field are structural analyses by both X-ray and neutron diffraction methods, and infrared and Raman spectroscopic measurements. Less frequently used techniques are nuclear magnetic resonance, both broad band NMR spectroscopy and magic angle spinning methods (MAS), nuclear quadrupole resonance (NQR), inelastic and quasielastic neutron scattering, conductivity and permittivity measurements as well as thermal analyses such as difference thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetry (TG and DTG) for phase transition studies. 

The experimental scatter for the differential scanning calorimetry values was reported to be within 4%, but it is not reported how well the authors equation corresponded to the measured values, or how well measurements obtained from the two techniques agree near 300 K. Unfortunately, the DSC data were not part of the supplementary material. 

Differential scanning calorimetry (DSC) is an experimental technique to measure directly the heat energy uptake that takes place in a sample during controlled increase (or decrease) in temperature. At the simplest... 

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