The new Rubotherm System Control Software (RSCS) allows the flexible configuration of thermogravimetric measurements. The measurement is then carried out automatically and the measured data is recorded and archived. Analysis and blank run correction of the experimental data is also performed fully automatically. The RSCS software turns Rubotherm’s DynTHERM instruments into fully automated analyzers for TGA measurements under realistic and process-relevant conditions.
For performing data analysis instrument-specific and measurement-specific parameters are determined automatically in blank measurement. The result of this blank measurement quasi represents the baseline for the subsequent TGA measurement. For determining the change in mass of the sample material, the blank measurement is subtracted from the thermogravimetric measurement with sample. The resulting sample mass changes during the measurement are provided to the user clearly in an online diagram and as tabulated data in files for further use.
A measurement is configured in segments. A segment is a part of the measurement with specific conditions for the reaction gas and the sample in the balance. The gas pressure, the gas flows (i.e. the composition of the reaction atmosphere), the heating rate and the sample temperature are selected for each segment. The desired values for these quantities are defined in a comfortable configuration by the user in form of a set-point table.
A complete measurement consists of a user defined number of segments with different pressures, gas flows, temperature ramps and sample temperatures. For the duration of each segment either a time-based or an event-based controller (for example on reaching a defined mass change of the sample) can be given. In case the event-based control is used, the software continuously determines the deviations of the selected measuring variable (pressure, temperature or sample weight) from the given threshold value. If this pre-set value is achieved the software automatically continues the measurement with the next segment. The event detection has the advantage that the segment durations will be adjusted automatically, and thus remain as short as possible.
All user-defined segments are processed automatically by time-controlled or event-controlled sequence. From the experimental results the sample mass change is determined in real time automatically by the correction with the blank measurement and displayed graphically in the software.
Of course, all the experimental data are continuously measured and recorded in data files. These values allow presentation and comparison of measured data in different diagrams by using Rubotherm’s data analysis software RTG. With RTG the further evaluation of the measured data is possible by subtracting different measurements, the application of data filtering and smoothing functions, the calculation of derivatives of the sample mass change and determination of the mean temperatures of mass loss steps (so-called “step transition temperature”).
The results can be combined automatically in a report and saved by only one click in a MS Word file. The export of the diagrams generated in RTG in various graphic formats plus the export of the data as ASCII file for further use in external mathematical / graphical software (such as MS Excel, Origin, SigmaPlot, ...) is also possible.
The following two diagrams show the results of a thermogravimetric measurement, evaluated with a RTG Software with Calcium Oxalate monohydrate (CaC2O4) as reference substance. In the first diagram the mass loss curve and the pressure of N2 atmosphere in a DynTHERM instrument is plotted as a function of sample temperature. The measurement was carried out at about 2.5 bar pressure. The mass losses of each step coincide with the expected stoichiometric weight loss. The decomposition steps are shifted to higher temperatures compared to measurements at ambient pressure – which is a known correlation. This proves that thermogravimetric measurements with Rubotherm DynTHERM devices determine quantitatively correct sample masses even at elevated pressures.
In the next diagram, the first derivative of the above mass loss curve (DTG) is presented. This representation of the data provides insight into the kinetics of mass loss.
The RSCS software is installed on DELL computers with MS Windows operating system and comes with the DynTHERM devices. The RTG software is supplied on a USB stick to install on user PC with MS Windows operating system.