Isothermal crystallization differential scanning calorimetry

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. ... 

KNUDSEN J c, ANTANUSE H s, RisBO j and SKIBSTED L H (2002) Induction time and kinetics of crystallization of amorphous lactose, infant formula and whole milk powder as studied by isothermal differential scanning calorimetry, Milchwissenschaft, 57, 543-546. 

A glass transition (-75°C) and two broad bands close to 0°C are obtained b y differential scanning calorimetry performed at the cooling rate of 10°C/min from 20°C to -150°C followed by an isothermal at this temperature for 10 min and then heated to 30°C at the same rate. If the heating rate is lowered to 2 or 1 °C/min, a crystallization peak is obtained at 10°C. 

Crystallinity was determined using differential scanning calorimetry. About 5-10 mg of an experimental agent was heated from 25 to 200°C at a heating rate of 20°C/ minute. The sample was isothermed at 200°C for 1 minute and then cooled at a cooling rate of 20°C/minute to ambient temperature. Crystallization data represents peak temperatures of exotherms in the cooling cycle and are summarized in Table 1. 

Fig. 3. Isothermal crystallization thermogram obtained by differential scanning calorimetry (DSC) indicating the determination of f, and reduced crystallinity (f) (adapted from Ref. 9).

Fig. 1. Differential scanning calorimetry (DSC) isothermal analysis curves of fat A. blank sample, B. sample with DK F-10, C. sample with P-170, D. sample with S-170 (Emulsifier concentration is 0.5%). Isothermal crystallization at 17°C (right side), and heating curves (left side), start at about 20°C at a rate of 5°C/min (rapidly cooled at a rateof 80°C/min). (Continued)...

In the work reported by Ng and Oh (2), an Avrami exponent of three was observed for palm oil from solid fat content (SFC) measurements. Using differential scanning calorimetry (DSC) to monitor the isothermal crystallization of palm oil, Kawamura (3) reported an Avrami exponent of four for palm oil. 

The overall crystallization kinetics of molten blends were analyzed by differential scanning calorimetry with a Perkin-Elmer DSC 2 apparatus. Following melting, the samples were heated at 85° C for 5 min. and isothermally crystallized at various T recording the heat of crystallization as a function of permanence time. The fraction of the material crystallized after time t was determined by means of the relation - Qt/Qoo> where Q - is the heat generated at time t and Qoo is the total heat of crystallization for t = . 

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. 

Differential scanning calorimetry was used to study the non-isothermal crystallization behavior of blends of poly(phenylene sulfide) (PPS) with the thermotropic liquid-crystalline copoly(ester amide) Vectra-B950 (VB) [126], The PPS crystallization temperature and the crystallization rate coefficient increased significantly when 2-50% VB was added. The Ozawa equation was shown to be valid for neat PPS as well as for the blends. The values of the Avrami exponents matched well against those determined previously using isothermal analysis, and they are independent of the concentration of VB. 

The effect of low absorbed doses of gamma radiation in the morphology and melting behaviour of isothermal crystallized iPP has been studied using X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. 

The crystallization kinetics of amorphous materials can be investigated either isothermally or non-isothermally by using thermal analysis techniques. In the isothermal method, the sample is heated above the glass transition temperature and the heat absorbed during the crystallization process is measured as a function of time. On the other hand, in the non-isothermal method, the sample is heated at a fixed rate and then the change in enthalpy is recorded as a function of temperature. Thermal analysis techniques such as differential thermal analysis (DTA) and differential scanning calorimetry (DSC) are quite popular for kinetic analysis of crystallization processes in amorphous solids (Araujo Idalgo, 2009 Malek, 2000 Prasad Varma, 2005). 

Al-Ghamdi, A.A., Alvi, M.A., Khan, S.A. (2011). Non-isothermal crystallization kinetic study on Gai5Se85-iAgc chalcogenide glasses by using differential scanning calorimetry. Journal of Alloys and Compounds, 509, pp. 2087-2093,0925-8835... 

Differential scanning calorimetry (DSC) is a thermal method commonly used to determine the hquid crystal phase transition during heating and cooling of a sample at controlled rate [5]. The DSC method measures the flux between the sample and a reference (an inert material - aluminum oxide, gold, etc.) subjected to the same (isothermal and dynamic) temperature program. There are two types of differential scanning calorimetry ... 

Differential scanning calorimetry (DSC) can be used to study the onset of crystallization on cooling from the melt where nudeated polymers have higher onset temperatures (Figures 2 and 3). Isothermal studies provide kinetic data where Avrami analysis (equation 2, where x = reduced... 

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