Weight based water vapor adsorption analyzerIt is the core equipment for accurately characterizing the moisture absorption performance of materials, and the operation must strictly follow the process specifications to ensure accurate experimental data and stable equipment operation. The following are the general operating steps for adapting to routine laboratory testing, which need to be adjusted according to the instrument model and experimental requirements:
1、 Preparation before the experiment
Sample pretreatment:
Select representative samples (solid powders, particles, films, etc.) with a quality control range of 10-100mg (matching the instrument balance range) to avoid weak or excessive signals affecting humidity response due to insufficient sample size.
Pre treat the sample according to experimental requirements: usually dry it in a 105 ℃ oven for 2-4 hours to remove residual moisture; Samples that are prone to decomposition or heat sensitivity can be dried under vacuum (40-60 ℃) to ensure that the samples are in a dry state.
After cooling to room temperature, remove the sample with powder free gloves to avoid contamination from sweat and dust on the hands.
Instrument and environmental inspection:
Confirm that the power supply of the instrument is stable, the connecting pipeline is not damaged or leaking, and the humidity sensor and balance are in normal working condition (the instrument self checks without any errors after startup).
The experimental environment should meet the following requirements: temperature of 20-25 ℃, humidity ≤ 60%, no obvious vibration or airflow interference (avoid near air conditioning vents, doors and windows), and prevent affecting the accuracy of the balance and humidity control.
Check if the desiccant inside the instrument (if any) is ineffective, replace it if necessary, and ensure that the inside of the instrument is dry.
Consumables and parameter preparation:
Prepare a clean sample tray (compatible with instruments such as quartz or aluminum sample trays), wipe it with anhydrous ethanol, and air dry to avoid residual impurities.
Pre set experimental parameters: temperature (usually 25 ℃), humidity gradient (such as 0% -95% RH, with a gradient of every 5% -10% RH), equilibrium time (usually 30-60 minutes, or set mass change ≤ 0.01% as the equilibrium standard), and adsorption desorption cycle times (1-3 times as needed).
2、 Sample loading and instrument debugging
Sample disk installation:
Open the instrument sample compartment door, use a special tool to place the empty sample tray on the balance bracket, close the compartment door, start the "blank calibration" program, deduct the sample tray mass (ensure that subsequent measurements only reflect changes in the sample's own mass).
After calibration is completed, open the cabin door and carefully spread the preprocessed sample evenly in the sample tray (to avoid excessive accumulation and affecting water vapor penetration). Gently place it back on the bracket to ensure that the sample tray is stable and not tilted.
Sealing and condition inspection:
Close the sample compartment door and confirm that it is well sealed (with no gaps or leaks). If the instrument has a vacuum function, briefly evacuate it and observe if the pressure is stable to rule out any leaks.
Start the instrument preheating program, wait for the temperature to reach the set value (fluctuation ≤ ± 0.5 ℃), the humidity sensor to stabilize (reading fluctuation ≤ 1% RH), and then proceed to the next step of operation.
3、 Experimental parameter setting and startup
Parameter input:
Create a new experimental method in the instrument operation software, input sample information (name, number, quality), and experimental conditions:
Temperature: Set a constant temperature (such as 25 ℃) and select "Temperature Constant Temperature Control".
Humidity program: During the adsorption stage, the humidity ranges from low RH to high RH (such as 0% → 5% → 10% →... → 95% RH), and during the desorption stage, the humidity ranges from high RH to low RH (such as 95% → 90% →... → 0% RH). Set the equilibrium conditions (time or mass change threshold) for each humidity point.
Protection parameters: Set the balance overload protection and humidity upper limit protection (to avoid exceeding the instrument range).
Experiment initiation:
After carefully checking the parameters, click "Start Experiment" and the software will automatically record the experimental data (time, RH, sample quality changes).
At the beginning of the experiment, observe the operating status of the instrument: the balance reading is stable, the humidity gradient switch is normal, there is no abnormal noise or alarm. If there is a problem, click "pause" immediately, and continue after troubleshooting.
4、 Experimental process monitoring
Real time observation data:
During the experiment, the changes in the adsorption desorption curve were monitored through software, with a focus on:
Does the quality change of each humidity point meet expectations (such as moisture absorbing materials should increase in weight with increasing RH, while hydrophobic materials show slight changes).
Whether the balance state meets the standard: If the quality continues to change after the set time, the balance time can be appropriately extended; If the quality fluctuates too much, check whether the sample is loose and whether the cabin door is sealed.
Exception handling:
If there is a malfunction in the humidity sensor (with unchanged readings or abnormal fluctuations), pause the experiment, calibrate the sensor, or contact maintenance.
If the sample falls off or the sample disk tilts, immediately stop the machine, reload the sample, and restart the experiment (note any abnormal conditions).
During the experiment, it is prohibited to open the cabin door at will to avoid damaging the stability of the experimental environment.
5、 Experiment completion and data export
Experimental termination:
After the adsorption desorption cycle is completed, the instrument automatically enters the "end program". After the humidity returns to the initial value (such as 0% RH) and the sample quality stabilizes, click "stop experiment".
If you need to terminate the experiment in advance, click "Pause" → "Confirm Termination" and indicate the reason in the experiment record.
Data export and saving:
View the raw data (time, RH, Δ m, equilibrium adsorption capacity, etc.), adsorption desorption isotherms, and kinetic curves in the software to confirm that the data is complete and without missing information.
Export data to a computer (format options include Excel, Origin, PDF), with naming conventions (such as "sample name temperature date"), and save the experimental method (for future repeated experiments).
6、 Instrument and sample post-processing
Sample processing:
Open the cabin door, use specialized tools to remove the sample tray, handle the sample properly (store or discard according to experimental requirements), and avoid sample residue.
Instrument cleaning:
Wipe the inner wall of the sample chamber and the balance bracket with a clean soft cloth to remove dust or sample residue; If any samples are spilled, clean them with a vacuum cleaner (specialized micro vacuum cleaner) to avoid contaminating the sensor or balance.
Close the cabin door, start the "instrument cleaning" program (if any), or blow the sample chamber with dry nitrogen for 10-15 minutes to keep the interior dry.
Instrument shutdown:
Follow the software prompts to close the experimental program, exit the operating software, and then turn off the instrument power and cut off the power supply.
Fill in the instrument usage log, recording the experimental date, sample information, running time, equipment status, and abnormal situations.
7、 Operation precautions
Sample pretreatment is crucial, as residual moisture can cause deviations in the calculation of adsorption capacity. Therefore, it is necessary to strictly follow the standard drying process.
When loading the sample tray, handle it gently to avoid colliding with the balance bracket and affecting the accuracy of the balance.
The humidity gradient setting should not be too large (recommended ≤ 10% RH/gradient), otherwise it may lead to insufficient balance and curve distortion.
The experimental environment should be kept stable to avoid frequent walking, vibration, or drastic temperature fluctuations by personnel.
Operators must be familiar with the operation of instrument software, and the first use must be carried out under the guidance of professional personnel. It is prohibited to modify core parameters (such as balance calibration parameters and humidity sensor calibration data) without authorization.