Rate from thermograms

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... 

Figure 6 Heating (a) and cooling (b) thermograms obtained with a-lactal-bumin (5% protein concentration, pH 6.5). ACpd is the heat capacity change between native and denatured forms /3 is the heating scanning rate. (From Ref. 190, with permission.)...

Fig. 10.2 Influence of heating rate on thermogram. Poly(butylene teiephthalate) sample cooled from 250°C at 10°Cmin then analyzed at indicated rates (a) 10°Cmin...

In a testing context, it refers to the first detection of exothermic-activity on the thermogram. The differential scanning calorimeter (DSC) has a scan rate of I0°C/min, whereas the accelerating rate calorimeter (ARC) has a sensitivity of 0.02°C/min. Consequently, the temperature at which thermal activity is detected by the DSC can be as much as 50°C different from ARC data. 

Differential Scanning Calorimeter (DSC) thermograms were obtained on a Perkin Elmer DSC-2 run at 10°C per minutes. Dynamic Mechanical Thermal Analysis (DMTA) spectra were obtained on a Polymer Labs DMTA at a frequency of 1Hz with a temperature range from -150°C to +150°C at a scan rate of 5°C per minute. 

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. 

The differential scanning calorimetry (DSC) thermogram of primaquine diphosphate was obtained using a DuPont TA-9900 thermal analyzer attached to a DuPont Data unit. The thermogram shown in Fig. 2 was obtained at a heating rate of 10 °C/min, and was run from 50 to 300 °C. The compound was found to melt at 209.8 °C. 

Heat-flow microcalorimetry may be used, therefore, not only to detect, by means of adsorption sequences, the different surface interactions between reactants which constitute, in favorable cases, the steps of probable reaction mechanisms, but also to determine the rates of these surface processes. The comparison of the adsorption or interaction rates, deduced from the thermograms recorded during an adsorption sequence, is particularly reliable, because the arrangement of the calorimetric cells remains unchanged during all the steps of the sequence. Moreover, it should be remembered that the curves on Fig. 28 represent the adsorption or interaction rates on a very small fraction of the catalyst surface which is, very probably, active during the catalytic reaction (Table VI). It is for these... 

Figure 2. TGA thermograms of products from dipropyltin dichloride (-----), tripropyltin dichloride ( ), dioctyltin dichloride (A/A/J, dibutyltin dichloride (-), diphenyltin dichloride (----------), and cotton itself (- -) at a heating rate of 20°C/min in air...

Figure 3. DSC thermograms of native CBH I and of fragments produced by limited proteolysis. For native CBH I and the core fragment, protein concentrations were in the range from 0.91 to 1.31 mg/ml. The concentration of the tail fragment was 0.41 mg/mL. Scan rate was 30 C/hr. Each division on the ordinate represents 20,000 cal/mol/deg.

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] ... 

The cure at Tc < Tgoo produces different DSC thermograms than the cure at Tc > Tgoo. For Tc = 80°C (< Tgoo), vitrification is attained when Tg equals Tc. This occurs somewhere between 14 and 20 h. From this time on, polymerization takes place at a very slow rate. A residual reaction heat is measured even after 264 h at 80°C. 

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