Ozawa method

Ozawa extended Avrami s theory to crystallization under non-isothermal conditions in a crystallization process at a constant rate. 

More than four DSC curves at different cooling rates were measured for the melt sample heat-treated at above the melting temperature for a given time, and the kinetic parameters can be obtained according to the equation [17]  

Deriving Eq. (4.11) with respect to 1/Tat fixed conversion degrees of decomposition, Eq. (4.12) is obtained  

The mean value of the preexponential factor Aj at each heating rate can be calculated from Eq. (4.13) [18]  

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The Ozawa method involves a relmement of this equation, namely dlnj8/d(l/r ) = -. Q52EJR,... 

A comparison of the kinetic parameters for the thermal decomposition of 2, 2 -azobis(isobutyronitrile) (AIBN) obtained by different DSC methods is given in Table 5.14 (184). The ASTM E-698 method is a modification of the Ozawa method (181), whereas the single scan DSC method is that described by Prime (182, 183). 

Table 4.2 Kinetic parameters obtained from Friedman, Kissinger, and Ozawa methods [12].

Figure 4.5 Determination of from Ozawa method (experimental data and fitted straight lines for different conversion degrees of decomposition) [12]. (With permission from Elsevier.)...

Using Ozawa method, the theoretic curves at different heating rates were obtained and compared well with the experimental results from [1], as shown in Figure 4.7 for all heating rates. 

DMA, the kinetic parameters of the glass transition can be determined by multicurves methods such as the Ozawa method (see Chapter 4). While only one heating rate is available here, the modified Coats-Redfern method is used [13, 14] as demonstrated in the following. Integration of Eq. (2.12) leads to ... 

A plot of In (j) against l/T, at a given fractional mass, yields a straight line from whose slope E can be calculated. Further, if the TG curves are plotted as fractional mass against VT at various heating rates the curves may be superimposed on each other by a lateral shift which is proportional to ln0. A master curve is thereby obtained. If the TG curves cannot be superimposed in this manner, the Ozawa method is not applicable. In practice, the degree of conversion at the DTG peak temperature varies with... 

Fig. 10.31 Illustration of the Ozawa method to treat (a) several DSC curves with various cooling rates a. (b) A group of crystallinity data Xc are read at a constant temperature, then (c) the Ozawa index can be obtained from the slope of lg[—ln(l — X )] versus lg(a)...

With a change of cooling rate, the temperature region for polymer crystallization shifts. The Ozawa method may not be easy to provide enough data points exhibiting a good linear relationship. Liu and Mo proposed a combination of Ozawa equation... 

Accordingly, on a series of crystallinity versus time curves (see Fig. 10.31b), one can take the data points along the horizontal equal-crystallinity line, and then obtain the ratios of the Avrami indexes and the rate constants separately from the slope and the intercept of log(fl) versus log(f)- The experiments have verified that a better linear relationship can be obtained in comparing this approach to the conventional Ozawa method. 

Determination of Apparent Activation Energy by Ozawa Method (Ozawa-Flynn-Wall Method) [9]... 

This method has an extra advantage over the modifed Ozawa method employed in the literature for the determination of activation energy of crystallization that the intercept of In (jS/ Tp) against 1000/ Tp gives the value of pre-exponential... 

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