DSC techniques

Temperature-risiag elution fractionation (tref) is a technique for obtaining fractions based on short-chain branch content versus molecular weight (96). On account of the more than four days of sample preparation required, stepwise isothermal segregation (97) and solvated thermal analysis fractionation (98) techniques usiag variatioas of differeatial scanning calorimetry (dsc) techniques have been developed. 

Changes in heat capacity and measurement of T for blends have been used to determine components of copolymers and blends (126—129), although dynamic mechanical analysis has been found to give better resolution. Equations relating T of miscible blends and ratios of components have been developed from dsc techniques, eg, the Fox equation (eq. 1), where f the blend, or is the weight fraction of component 1 or 2,... 

It explodes without melting when heated [1]. The title compound and its barium, lead(II), and mercury(II) salts were studied by DTA and DSC techniques. The lead salt is the least stable and most powerful primary explosive of the 4 compounds [2],... 

The DSC technique enables crystalline materials to be characterised by their melting point. Additives that come into this category include hydrocarbon waxes and poly(tetrafluoroethylene) (PFTE) lubricant. The presence of PTFE in low friction acetal mouldings can be established from the detection of the PTFE melting endotherm at 320°C. 

In many respects, differential scanning calorimetry (DSC) is similar to the DTA method, and analogous information about the same range of thermal events can be obtained. However, DSC is far easier to use routinely on a quantitative basis, and for this reason it has become the most widely used method of thermal analysis. The relevance of the DSC technique as a tool for pharmaceutical scientists has been amply documented in numerous reviews [3-6,25-26], and a general chapter on DSC is documented in the U.S. Pharmacopeia [27]. 

Since DSC is a quantitative technique, the enthalpies determined for reactions can be used for analytical purposes. For instance, a method has been described whereby the water content in hydrate species can be determined using DSC techniques [35]. In this method, it was assumed that the enthalpy of binding n moles of water molecules in a hydrate is the same as that of n moles of water... 

Some scientists describe DSC techniques as a subset of DTA. DTA can be considered a more global term, covering all differential thermal techniques, while DSC is a DTA technique that gives calorimetric (heat transfer) information. This is the reason that DSC has calorimetry as part of its name. Most thermal analysis work is DSC, and Sections 15.3.3 and 15.3.4 provide information about the instrumentation and applications of this technique. 

Chlorinated silicone oil (DC200, with 15, 30 or 40% chlorine content structure shown has 32%) decomposed violently on heating. Thermal stability decreased with increasing chlorine content and was investigated by TGA and DSC techniques. 

Determination of the reaction rate from calorimetric measurements, using DSC technique, is very useful and was applied with success for many template polymerization systems and for blank polymerizations.Two types of calorimetric measurements were described isothermal and scanning experiments. The heat of polymerization can be measured by DSC method, measuring thermal effect of polymerization and ignoring the heat produced from decomposition of the initiator and heat of termination. In isothermal experiments sample is placed at a chosen temperature and thermogram is recorded versus time. Assuming typical relationship... 

In Chapter 2 the DSC technique is discussed in terms of instruments, experimental methods, and ways of analysing the kinetic data. Chapter 3 provides a brief summary of epoxy resin curing reactions. Results of studies on the application of DSC to the cure of epoxy resins are reviewed and discussed in Chapter 4. These results are concerned with the use of carboxylic acid anhydrides, primary and secondary amines, dicyanodiamide, and imidazoles as curing agents. 

Moreover, the DSC technique investigates other types of deviations, such as the effect of the solvent or catalytic effects due to impurities. 

The SP-DSC has a lower instrumental cost and is simpler and safer to operate, while the HP-DSC technique has a lower operational cost and does not require sample preparation (shorter total analysis time). 

The transition of a number of phospholipid chains from an ordered to a disordered state is of direct relevance to the state of the cell membrane - it is a characteristic parameter for each phospholipid. The dynamic molecular organization in vesicles and membranes has been described in detail [15] and is shown schematically in Figure 3.3. Using the thermodynamic DSC technique, changes in phase transition... 

The TG-DSC technique has recently been reviewed [56]. Redfern [57] has reviewed single sample simultaneous thermal analysis, i.e., TG-DSC and TG-DTA studies of polymers. 

Table I shows the Tg values obtained in this work on standard polystyrene samples in most cases, the values obtained from DTA data are slightly higher than those obtained by DSC. Since these data were to be used for detailed comparisons with data obtained by others as well as by ourselves on styrene block copolymers, we first compared our data on anionically polymerized standard polystyrenes with those obtained on other anionically polymerized polystyrenes by other workers also using DTA and DSC techniques. This comparison is shown graphically in Figure 1. In Figure 1, the solid curve is drawn through a combination of our data with that obtained by Wall et al. (25) using a Dupont 900...

A study of the kinetics of thermal decomposition reactions using pentaerythritol tetranitrate(PETN), a high explosive, as the model substance was first conducted by SC-DSC. In this study, information was obtained that was relative to the characteristics of the DSC technique. However, the question as to how the results of analyses of this type were useful for practical work arose, and studies in this area were stopped. Subsequently, studies have proceeded on the evaluation of hazards by collecting as much data on self-reactive substances as possible. 

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