Kinetic Software

The needed thermochemistry for many thousands of molecules is available from standard sources such as the JANAF tables. " Polynomial fits of this data in the form required by our kinetics software are also available. However, experimental thermochemical data is often lacking for many of the intermediate species that should be included in a detailed kinetics mechanism. Standard methods have been developed for estimating these properties, discussed in detail by Benson. ... 

With the possibility that dozens or even thousands of elementary chemical reactions may have to be included in a complex reaction mechanism, the need for a general and compact formalism to describe detailed reaction kinetics becomes apparent. Chemkin [217] is a widely used chemical kinetics software package designed to aid in such complex reaction kinetics calculations. 

Schumacher E (1997) DETMECH Chemical Reaction Kinetics Software. In ... 

Sichina, WJ, Prediction of epoxy cure properties using Pyris DSC Scanning Kinetics Software, Perkin Elmer Instruments, Application Note, Thermal Analysis, PETech-48 2000. 

H NMR spectra were recorded on Briiker ACP 400 or DPX 400 spectrometers using deuterated solvents obtained from CEA or Aldrich. Polymerization kinetics, followed by NMR, were recorded using the Briiker built-in kinetics software. Molecular mass analyses were carried out by gel permeation (size exclusion) chromatography on a Polymer Laboratories system. THF was the eluent at 1.0 mL min with a PL-gel 5 jim (50 X 7.5 mm) guard column, two PL-gel 5 pm (300 x 7.5 mm) mixed-C columns with a refractive index detector. Samples were compared against narrow standards of poly(methyl methacrylate), A/p = 200 to 1.577 x 10 g mol , obtained from Polymer Laboratories, except for methyl methacrylate dimer, trimer, and tetramer which were prepared by catalytic chain transfer polymerization at the University of Warwick. 

A comparative investigation of the applicability of commercial kinetics software was carried out using ... 

Here, we should make the following comment. Noteworthy, most chemists starting studies in this field, in general are not familiar with the relevant mathematical methods and the details of computer software. This, in turn, causes certain difficulties in analyzing the obtained results. In our opinion, the added complication is in the lack of confidence of many researchers in completely understanding the currently used kinetic software. Surely, successful computations carried out using these programs will serve as a positive factor. 

So, it can be summarized that the kinetic software codes undoubtedly are the powerful tool in hands of researchers, but their usage requires a creative approach. It is not difficult to predict that degree of active manual calculations will decrease considerably over the time. 

It is important that the value method of studying complex chemical reactions is easily compatible with computational methods of calculation. This emphasis is validated by the kinetic software package VALKIN described here. 

A generalization of this example to multi-well and multi-channel systems is straightforward and easily implemented in kinetic software (discussed later). All integrals are replaced by finite sums and energy graining will be one important input parameter to such codes. 

Rates of reaction of both these types of curing experiments are very useful to polymer scientists. There are several different kinetics software packages available to characterize materials. There are scanning kinetics, isothermal kinetics and model-free kinetics calculations. Each has its own unique application or is best suited for certain applications. Figure 6 depicts the thermal curve of an epoxy cure with a second curve superimposed representing the percent area as the reaction advances. 

Combining these results with Eq. (6.8) and using the proper model, for example, the Arrhenius approach, yields an equation that connects the measured quantities

kinetic parameters n, A, and Tact- Such an equation can only be solved numerically. Nowadays powerful sofiware is available that does the job of determining the kinetic parameters from the measured heat flow rate function. But to get reliable results, the proper kinetic model must be selected first. The theory behind it is not simple, and a lot of experience is necessary to handle the rather complex kinetic software. 

Model-free kinetics software employs numerical integration methods to measure activation energy versus conversion from cure exotherms at three or more heating rates, or from isothermal data at three or more temperatures. In both cases a minimum of four runs is recommended. Predictions like conversion-time plots and calculated DSC curves are made using Eq. (3.31). An advanced version of MFK software allows analysis of data from arbitrary heating programs, such as combined ramp and isothermal. A drawback of the commercial software is that a discrete mathematical relationship is not produced that can be exported and incorporated into cure models. 

The decomposition kinetic analysis of the mass loss curves was carried out using standard TGA kinetics software that is based on the Flynn-Wall method (Flynn and Wall 1966a,b) and described in Section 3.5.5. In this technique a plot of the logarithm of the heating rate (log q) against the reciprocal of the absolute temperature [see. Eq. (3.23)] was made where the conversion or mass loss equaled 4%, 5.5%, 8%, 12%, 18% and 26%. From the slope of this plot (Fig. 3.32) the activation energy for decomposition E) was calculated from Eq. (3.32), which is based on Eq. (3.23) ... 

In this section we briefly review commercial thermogravimetric analyzers in alphabetical order of manufacturer. Please visit the respective supplier Websites for current offerings and more information. See Section 3.2.1 for descriptions of balance configurations. While most suppliers offer autostep-wise software to control the furnace temperature (see Fig. 3.40), kinetics software such as the ASTM El 641 Flynn-Wall method described in Section 3.5.5, and the ability to interface to a Fourier transform infrared spectrometer (FTIR) or mass spectrometer (MS), the reader interested in these applications is advised to confirm the features of particular TGA systems. 

The purpose of the non-isothermal study was then to determine at the same time the values of the energy of activation and n with only one experiment. A certain number of suppliers of apparatuses (thermogravimetiy) propose kinetics software that makes it possible to use these methods to determine the energy of activation, and n. Of coiu e, if the basic assumptions of these expressions do not apply, we always obtain a value of the energy of activation and a value of n with no physical meaning and even changing with time ... 

This is the so-caUed Arrhenius plot. Since the slope is dependent upon activation energy, plots of these types are often displayed within kinetics software to allow the operator to check the consistency of the data. This is of particular value where isothermal data are obtained at a series of different isothermal temperatures. A similar expression can be derived for kinetics based on a series of different scan rates, and results in an Arrhenius plot of scan rate versus reciprocal temperature. These plots are then checked at a series of desired conversions. 

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