Isothermal method, differential scanning calorimetry

The kinetics of copolymerization or curing of epoxy resins with cyclic anhydrides initiated by tertiary amines was investigated by chemical analysis 52,65,73,74,90) differential scanning calorimetry isothermal methods electric methods , dynamic differential thermal analysis , IR spectroscopy dilatometry or viscometry Results of kinetic measurements and their interpretation differ most authors agree, however, that the copolymerization is of first order with respect to the tertiary amine. 

Differential Scanning Calorimetry (DSC) This is by far the widest utilized technique to obtain the degree and reaction rate of cure as well as the specific heat of thermosetting resins. It is based on the measurement of the differential voltage (converted into heat flow) necessary to obtain the thermal equilibrium between a sample (resin) and an inert reference, both placed into a calorimeter [143,144], As a result, a thermogram, as shown in Figure 2.7, is obtained [145]. In this curve, the area under the whole curve represents the total heat of reaction, AHR, and the shadowed area represents the enthalpy at a specific time. From Equations 2.5 and 2.6, the degree and rate of cure can be calculated. The DSC can operate under isothermal or non-isothermal conditions [146]. In the former mode, two different methods can be used [1] ... 

Stavinoha and Kline (2001) adapted ASTM method D 6186 (Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry [P-DSC]) for analyzing the oxidative stability of SME treated with antioxidants. This report concluded that isothermal P-DSC analysis is suitable for screening the effectiveness of antioxidants for treating biodiesel. 

Chrzanowski FA, Ulissi LA, Fegely BJ, Newman AC. Preformulation excipient compatibility testing, application of a differential scanning calorimetry method versus a wet granulation simulating isothermal stress method. Drug Dev Ind Pharm 1986 12 783-800. 

Despite the great diversity in the design of microcalorimeters and the experimental procedures described in the literature [1-10], only two microcalorimetric methods have found widespread application in cydodextrin (CyD) studies and drug-design research. These two methods are differential scanning calorimetry (DSC) and isothermal titration microcalorimetry (ITC). DSC and ITC can be con-... 

Differential scanning calorimetry (DSC) is a sensitive method which has enabled changes in biological systems to be examined providing medical researchers with distinct opportunities. Other thermoanalytical techniques such as thermogravimetry (TG) and isothermal titration calorimetry (ITC) are useful in the evaluation of thermal stability and to measure the heat generated in physical and chemical reactions. 

A study of the relaxational transitions and related heat capacity anomalies for galactose and fructose has been described which employs calorimetric methods. The kinetics of solution oxidation of L-ascorbic acid have been studied using an isothermal microcalorimeter. Differential scanning calorimetry (DSC) has been used to measure solid state co-crystallization of sugar alcohols (xylitol, o-sorbitol and D-mannitol), and the thermal behaviour of anticoagulant heparins. Thermal measurements indicate a role for the structural transition from hydrated P-CD to dehydrated P-CD. Calorimetry was used to establish thermodynamic parameters for (1 1) complexation equilibrium of citric acid and P-CD in water. Several thermal techniques were used to study the decomposition of p-CD inclusion complexes of ferrocene and derivatives. DSC and derivative thermogravimetric measurements have been reported for crystalline cytidine and deoxycytidine. Heats of formation have been determined for a-D-glucose esters and compared with semiempirical quantum mechanical calculations. ... 

The kinetics of curing of a poly(phenylene ether)/epoxy resin system has been investigated by an advanced iso-conversional method. Curing experiments with different PPE/EP ratios were carried out using non-isothermal differential scanning calorimetry. It was shown that the curing mechanism of this system is very complicated [21],... 

In differential scanning calorimetry (DSC), the sample is not heated at a constant rate, but a definite quantity of heat is either added or taken away isothermally. This method is particularly suited to measure the heats of fusion at crystallization or to follow the course of crystallization at a given temperature. 

The experimental procedure involves initiation of the polymerization by irradiation followed by cutting off the light after a certain time at a degree of conversion chosen, and monitoring the reaction in the dark. As experimental methods, both isothermal differential scanning calorimetry (photocalorimetry, photo-DSC) [2,6, 7, 18-32] and real-time infrared... 

The amorphous nature of these powders was confirmed by several techniques, including X-ray powder diffraction and electron-beam microdiffraction, differential scanning calorimetry, and transmission electron micrography, which reveal the powder microstructure. Moreover, the material shows a surface area as high as 120 m2 g-l (by the BET gas adsorption isotherm method), i.e., 150 times larger than a commercially available 5 pm-diameter iron powder. 

The term calorimetry denotes a variety of measurement methods which involve a measurement of the heat of physical or chemical changes in a sample. One of the most commonly used calorimetric methods is differential scanning calorimetry in which the difference in the heat flow rate to a primary sample and a reference sample is measured, when both are subjected to the similarly alternating temperature. Usually this is done in a specified, controlled atmosphere. In isothermal calorimetty the measurement temperature is kept as constant as possible, and, instead of temperature alternation, the other environmental parameters such as gas atmosphere, relative humidity, light exposure, etc., are alternated. 

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