4.9. REAL ATMOSPHERIC TEMPERATURE MODE: Prediction of the reaction progress (-) and reaction rate d/dt (s-1) for real atmospheric temperature profiles which allows the investigation of the properties of low-temperature decomposed solids under different climates (yearly temperature profiles with daily minimal and maximal fluctuations).




Figure: Available climates for the determination of the thermal stability of substances. Possible extension to a database containing more than 7000 different climates.

Example:

Let us calculate the solid state reaction extent of a low-temperature decomposed substance in Las Vegas, New York and Quebec (see next figure). It can be seen that within 10 years, the degree of the decomposition amounts to about 50 % in Quebec whereas in Las Vegas and New York full conversion is reached after 2 and 6 years, respectively.



Figure: Reaction progress (DSC, normalized signals) of a low-temperature decomposed substance as a function of time for the Las Vegas, New York and Quebec temperature profiles.



Figure: Reaction rate d/dt (DSC, normalized signals) of a low-temperature decomposed substance as a function of time for the Las Vegas, New York and Quebec temperature profiles.



Figure: Average daily minimal and maximal temperatures recorded for each day of the year between 1961 and 1990 (Las Vegas, New York and Quebec).


Comments:

The important goal of the investigation of the kinetics of the thermal decomposition of solids is the need to determine the thermal stability of substances, i.e. the temperature range over which a substance does not decompose with an appreciable rate. The correct prediction of the reaction progress of materials which are unstable under ambient conditions (food, drugs, some polymers, etc.) requires accurate application in the calculations of both:
- the kinetic parameters
- the exact temperature profile for a given climate

Calculations can be achieved for any fluctuation of the temperature which makes possible the predictions of thermal stability properties for varying climates. Exact consideration in the calculations of daily minimal and maximal temperature variations of worldwide climates provides very valuable insight when interpreting and quantifying the reaction progress of materials subjected to atmospheric conditions.