Differential scanning calorimetry heating rates

The microanalytical methods of differential thermal analysis, differential scanning calorimetry, accelerating rate calorimetry, and thermomechanical analysis provide important information about chemical kinetics and thermodynamics but do not provide information about large-scale effects. Although a number of techniques are available for kinetics and heat-of-reaction analysis, a major advantage to heat flow calorimetry is that it better simulates the effects of real process conditions, such as degree of mixing or heat transfer coefficients. 

FIG. 10 Differential scanning calorimetry heating thermograms of compositions (Fig. 9). Heating rate = 10°C/min. 

From differential scanning calorimetry (dsc) data from Technochemie GmbH—Verfahrenstechnik. Heating rate = 10° C/min ... 

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. 

DSC (differential scanning calorimetry) was performed using a Netzsch Phoenix El apparatus. Typically, samples of about 20 mg were applied in aluminium cold-sealed crucibles with heating/cooling rates of 5 °C/min. 

Differential Scanning Calorimetry. A sample and an inert reference sample are heated separately so that they are thermally balanced, and the difference in energy input to the samples to keep them at the same temperature is recorded. Similarly to DTA analysis, DSC experiments can also be carried out isothermally. Data on heat generation rates within a short period of time are obtained. Experimental curves from DSC runs are similar in shape to DTA curves. The results are more accurate than those from DTA as far as the TMRbaiherm is concerned. 

We use differential scanning calorimetry - which we invariably shorten to DSC - to analyze the thermal properties of polymer samples as a function of temperature. We encapsulate a small sample of polymer, typically weighing a few milligrams, in an aluminum pan that we place on top of a small heater within an insulated cell. We place an empty sample pan atop the heater of an identical reference cell. The temperature of the two cells is ramped at a precise rate and the difference in heat required to maintain the two cells at the same temperature is recorded. A computer provides the results as a thermogram, in which heat flow is plotted as a function of temperature, a schematic example of which is shown in Fig. 7.13. 

Another important technique is the thermal analysis technique of differential scanning calorimetry (DSC). Current high-speed DSC equipment (sometimes also referred to as hyper-DSC) allows for rapid heating (up to 500°C/min) and cooling of (small) samples and therefore an increased rate of analysis per sample... 

The differential scanning calorimetry (DSC) thermogram of miconazole was obtained using a DuPont 2100 thermal analyzer system. The thermogram shown in Fig. 2 was obtained at a heating rate of 10°C/min and was run over the range 50—300 °C. Miconazole was found to melt at 186.55 °C. 

The differential scanning calorimetry (DSC) thermogram of niclosamide was obtained using a General V4 IC DuPont 2100. The data points represented by the curve shown in Fig. 2 were collected from 200 to 400°C using a heating rate of 5°C/ min. It was found that the compound melted at 231.66°C with an enthalpy of fusion equal to 69.31 J/g. 

Measurements of differential scanning calorimetry (DSC) were obtained on a TA Instruments 2910 thermal analysis system (Fig. 2). Samples of approximately 1-2 mg were accurately weighed into an aluminum DSC pan, and covered with an aluminum lid that was crimped in place. The samples were then heated over the range of 20-140 °C, at a heating rate of 10 °C/min. Valproic acid was found to boil at 227 °C. 

The photostability of two polymorphs of nicardipine hydrochloride have been studied using a number of techniques [95]. After irradiation, the drug substance decomposes to a pyridine derivative, and the photodegradation of the /1-form exceeded that of the x-form. It was also found that the color of the two different forms differed with the polymorphic state, but that grinding the two forms lessened the difference in their photochemistries. A correlation between the heat of fusion (measured by differential scanning calorimetry) and the photodegradation rate constant was observed. 

In differential scanning calorimetry, the selected chemical reaction is carried out in a cmcible and the temperature difference AT compared to that of an empty crucible is measured. The temperature is increased by heating and from the measured AT the heat production rate, q, can be calculated (Fig. 3.19). Integration of the value of q with respect to time yields measures of the total heats... 

Differential scanning calorimetry (DSC) was designed to obtain the enthalpy or the internal energy of those processes and also to measure temperature-dependent properties of substances, such as the heat capacity. This is done by monitoring the change of the difference between the heat flow rate or power to a sample (S) and to a reference material (R), A

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Figure 11.5 Differential scanning calorimetry scans of (a) a slowly cooled, and (b) a rapidly quenched PTT sample (heating rate, 10 °C/min)...

The two most popular methods of calculation of energy of activation will be presented in this chapter. First, the Kissinger method [165] is based on differential scanning calorimetry (DSC) analysis of decomposition or formation processes and related to these reactions endo- or exothermic peak positions are connected with heating rate. The second method is based on Arrhenius equation and determination of formation or decomposition rate from kinetic curves obtained at various temperatures. The critical point in this method is a selection of correct model to estimate the rate of reaction. 

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