Multiple heating rate

By applying multiple heating rate DSC measurements and Ozawa s isoconver-sional model free method, an activation energy of 34.2 kcal mol1 and pre-exponential factor of 1.99 1012 s 1 were calculated from the DSC peak maximum temperature - heating rate relationship. 

The kinetics of the cure of ATS at 130°C in nitrogen determined by various methods are shown in Figure 1. The dashed curve represents the prediction based on kinetic parameters determined by analysis of scanning DSC data by the method of multiple heating rates described previously (8). This method utilizes a rate equation of the form ... 

Multiple Heating Rate Data. The major effort of this study has been to correlate the data in a model which will be valid for multiple heating rates. The advantage of the AH model was more evident for this purpose. Three models were used to correlate the multiple heating rate data 1) CR-LM, 2) AH-LM, and 3) CR-AH-LM. A comparison of the correlated results of these three models is presented in Table IX. From Table IX, it can be seen that ... 

The CR model is not suitable for correlating multiple heating rate data as the AAD values were much higher than those of the other models. 

For most sets of multiple heating rate data investigated, both the AH-LM and CR-AH-LM models give a reasonably good fit. 

Fig. 9. Master cure curve for polyurethane pultrusion resin system. Data points from isothermal DSC and DSC simulated cure profiles were shifted to times at 80°C by means of equation 14 using the activation energy measured from multiple heating rate DSC. The solid line is calculated from the second-order kinetic equation found to fit the master...

Kinetic analyses of multiple nonisothermal, also referred to as multiple heating rate, runs are most commonly performed by using the methods of Friedman, Ozawa, and Flynn and Wall. However, application of the Kissinger method (Kissinger 1957) is discouraged because the method yields a single value of... 

TGA Isothermal or non-isothermal analysis Constant or multiple heating rates Thermal and/or oxidative stabilities and compositional properties Decomposition temperature (thermal stability) Percentage of mass loss and residue Temperature of thermal degradation beginning, maximum and total decomposition Total mass loss Activation energies evolution Kinetic models... 

Plotting ln[g(a)] versus ln(q) and using the method of least squares linear regression, if the mechanism studied conforms to certain g(a) function, the slope of the straight line should be equal to -1.0000 and the linear correlation coefficient should be equal to unity. The values of E and A do not influence the shape of the most correct reaction mechanism function determined. In order to determine of the most probable mechanism function, the values of the conversion a corresponding to multiple heating rates taken at the same temperature were put into the left side of Eq. (22.20) and all the 35 types of mechanism functions presented in Table 22.2 were tested. The slope and correlation coefficient were obtained from the plot of ln[g(a)] versus ln q). The most probable... 

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