Differential scanning calorimetry heating curves

Fitting Differential Scanning Calorimetry Heating Curves for Polyetherimide Using a Model of Structural... 

Fig. 8 Differential scanning calorimetry heating curves of PBS crystallized at different temperatures, a PBS with about 2.5 x 10 (Yasuniwa et al. 2005), b PBS with about 6,800 (Papageorgiou and Bikiaiis 2005)...

FIGURE 4.1 Differential scanning calorimetry heating and cooling curves of glyceryl tri-palmitate (Dyn 116) bulk material, with microparticles prepared by solvent evaporation and microparticles prepared by melt dispersion 1 d after the preparation. The plots are displaced vertically for better visualization. (Adapted from [13] with permission from Elsevier.)... 

Figure 4.3 shows a sample temperature-heat flow differential scanning calorimetry (DSC) curve obtained for high-density polyethylene using a PerkinEImer DSC-7 instrument. It illustrates the measurement of the T and heat of melting in a single run. 

Modulated differential scanning calorimetry (MDSC) curves were obtained using a Universal V2.4F TA spectrometer. First scan MDSC heating curves were obtained by heating at 5 C min to the desired temperature. Second scan MDSC heating curves were obtained by first cooling the sample after the first heating in the instrument over ca. 17 min. The sample was then heated at 5 °C min to the desired temperature. 

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. 

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. 

Figure 6. Differential scanning calorimetry scans of 1c polymers. Curves are displaced vertically. Conditions heating, 20 K/min and cooling, 320 K/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. 

More advanced techniques are now available and section 4.2.1.2 described differential scanning calorimetry (DSC) and differential thermal analysis (DTA). DTA, in particular, is widely used for determination of liquidus and solidus points and an excellent case of its application is in the In-Pb system studied by Evans and Prince (1978) who used a DTA technique after Smith (1940). In this method the rate of heat transfer between specimen and furnace is maintained at a constant value and cooling curves determined during solidification. During the solidification process itself cooling rates of the order of 1.25°C min" were used. This particular paper is of great interest in that it shows a very precise determination of the liquidus, but clearly demonstrates the problems associated widi determining solidus temperatures. 

Many different test methods can be used to study polymers and their physical changes with temperature. These studies are called thermal analysis. Two important types of thermal analysis are called differential scanning calorimetry (DSC) and differential thermal analysis (DTA). DSC is a technique in which heat flow away from a polymer is measured as a function of temperature or time. In DTA the temperature difference between a reference and a sample is measured as a function of temperature or time. A typical DTA curve easily shows both Tg and T . 

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] ... 

Differential Thermal Analysis (DTA) — A procedure for recording the difference in temp between a substance and a reference material, against either time or temp as the two specimens are subjected to identical temp regimes in an environment heated or cooled at a controlled rate. The record is the differential thermal or DTA curve the temp difference (A T) is usually plotted on the ordinate with endothermic reactions downward and time or temp on the abscissa increasing from left to right Differential Scanning Calorimetry (DSC) —... 

Isothermal differential scanning calorimetry (DSC) tests were performed on three unsaturated polyester (UPE) samples at three different temperatures (100°C, 110°C, and 120°C). The output for the three DSC tests are presented in the Fig. 2.70. On the graph, label which curve is associated with which test temperature. From the curves in Fig. 2.70 estimate the total heat of reaction, Qt ... 

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