The new Rubotherm System Control Software (RSCS) allows the flexible configuration of sorption measurements. The measurement is then carried out automatically and the measured data is recorded and archived. Data analysis is also performed fully automatically. The RSCS software turns Rubotherm’s IsoSORP devices into fully automated analyzers for sorption measurements under realistic and process-relevant conditions.
For performing data analysis instrument-specific and sample-specific parameters are determined automatically in blank and buoyancy measurements. With these parameters the experimental sorption data is processed by a sophisticated mathematical model based on the physical principle of the measurement methodology. The measuring results are provided to the user clearly in an online isotherm or isobar 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 in case of a FlexiDOSE FLOW dosing system - and the sample temperature (and where necessary the heating rate) 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 and temperatures (maybe temperature ramps). For the duration of each segment either a fixed time or equilibrium condition can be specified.
When using equilibrium conditions, the software continuously determines the deviations of the measured values of pressure, temperature and sample mass from their moving average within a certain period which can be set by the user. Once these deviations are less than the tolerable threshold set by the user, the software recognizes this point as equilibrium state. Then automatically it starts the next segment (or measuring point) of the sorption measurement. The equilibrium detection has the advantage that the segment’s durations are adjusted automatically, and thus remain as short as possible. The equilibrium criteria (time duration for moving average calculation, tolerable threshold of pressure, temperature and sample mass from their averages) are pre-set by the user but can also be adjusted during the measurement.
All segments defined by the user are automatically processed with the time-controlled or equilibrium-controlled sequence. From the measuring results at the end of the segments (usually equilibrium values) the adsorption isotherm is determined automatically by performing the buoyancy correction. The resulting isotherm is plotted online on the software screen.
For isobaric, non-isothermal measurements, the sample mass is determined and plotted in a similar diagram as function of the temperature.
Absolute adsorption data may be calculated on user’s demand from the excess adsorption isotherm determined automatically by the software. Therefore, the software can determine automatically the density of the adsorbed phase from the negative slope of the excess isotherm in the highest pressure / density range. Alternatively - for instance if no measured values are recorded at high pressures and consequently no declining part of the isotherm exists - the user has the option to specify manually the density of the adsorbed phase. Using this value the absolute adsorption isotherm is calculated and plotted in a separate diagram. From the shape of this calculated absolute adsorption isotherm it can be estimated, whether or not the used density of the adsorbed phase is physically meaningful.
Of course, all the experimental data are continuously measured and recorded in data files. These values allow, for example, analysis and illustration of the kinetics of sorption process with an external mathematical / graphical software (such as MS Excel, Origin, SigmaPlot, ...). The following diagram shows an example of an evaluation of the kinetics of sorption of CO2 in a polymeric material at 120°C.
The RSCS-software is installed on DELL computers with MS Windows operating system and comes with the IsoSORP devices.