Overview
The hot melt glue ash content tester works based on the principle of high temperature burning. The core process is to fully burn the hot melt adhesive sample under specific high temperature conditions, so that the organic components are completely decomposed and volatilized, and the final residual inorganic matter is ash. By measuring the mass change of the sample before and after burning, the ash content can be accurately calculated. The calculation formula is as follows:
Ash content (%) = (M3 - M1) / (M2 - M1) × 100%
Among them, M1For the mass of the empty crucible, M2For the crucible before burning and the total mass of the sample, M3The total mass of the crucible and ash after burning. This method refers to a number of common standards for the determination of material residues.
Preparation before operation
In order to ensure the accuracy and operation safety of the measurement results, the following preparations must be completed before the experiment. First, check whether the power supply line, high temperature furnace and exhaust system of the meter are normal. Secondly, prepare laboratory equipment, including a clean crucible with a constant weight, a dryer, an analytical balance, and a high-temperature sampling and weighing tool. Finally, ensure that the laboratory is well ventilated and that personal protective equipment such as heat-resistant gloves and goggles are available.
Sample preparation is a critical step. The hot melt sample to be tested should be evenly mixed and cut or ground into suitable small pieces or particles to ensure that it can be heated evenly and completely burned in the crucible. It is recommended that the initial quality control of the sample be between 2 and 5 grams, which needs to be adjusted according to the estimated ash content and instrument specifications.
Assay steps
This section details the complete operation process from weighing to calculation. Please follow the step order exactly.
Step 1: The empty crucible is always heavy
The clean crucible is placed in a high-temperature furnace and burned to a constant weight at a set temperature (e.g., 550±25°C). After taking it out, it is cooled in a dryer to room temperature, and its mass M is accurately weighed with an analytical balance1。 Repeat the burning, cooling, and weighing process until the difference between two consecutive weighing values does not exceed the specified value (e.g., 0.3 mg).
Step 2: Sample weighing and loading
The prepared hot melt glue sample is placed in a crucible with a constant weight, and the total mass of the crucible and the sample is accurately weighed using an analytical balance2。 The net weight of the sample (M) was recorded2 - M1）。 When loading, make sure that the sample is laid flat at the bottom of the crucible to avoid excessive accumulation.
Step 3: Low-temperature carbonization
The crucible containing the sample is placed in a low-temperature area of an electric heating plate or muffle furnace for initial carbonization. This process involves slow heating to prevent the sample from splashing or spilling due to rapid decomposition. Wait until the sample is completely carbonized and no more smoke is generated.
Step 4: High-temperature burning
The carbonized crucible is transferred to the central area of the high-temperature furnace that has been preheated to a specified temperature (typically 550°C to 850°C, depending on the relevant standard or material properties). The burning time should ensure that the sample is completely ashed, usually no less than 2 hours. When the burning is complete, turn off the heating power.
Step 5: Cooling and weighing
After the furnace temperature drops below 200°C, use crucible tongs to move the crucible to the dryer, cover the lid tightly, and cool to room temperature. Accurately weigh the total mass of the crucible and ash M using an analytical balance3。 If incomplete ashing is suspected, the high-temperature burning, cooling and weighing steps can be repeated until a constant weight is reached.
Step 6: Result calculation and recording
The obtained quality data will be M1, M2, M3Substituting the above calculation formula can obtain the percentage of ash content. At least two samples should be measured in parallel, the calculation results should be averaged, and all raw data and calculations should be recorded.
Notes:
Safety and precision are the core concerns of the operating process. The following points must be strictly observed.
| High temperature operation | Use special tools to remove and place the crucible throughout the process to avoid burns. Do not touch the high-temperature part of the furnace during burning and cooling. |
| Sample handling | During the carbonization stage, the heating rate should be controlled to prevent losses caused by sample deflagration or spillage. |
| Environmental control | The cooling process must be carried out in the dryer to prevent moisture absorption from the ash from affecting the weighing accuracy. |
| Instrument calibration | Regularly use reference materials to verify instrument temperature accuracy and calibrate analytical balances as scheduled. |
| Furnace cleaning | After each experiment, it is necessary to clean up any residues that may exist in the furnace to keep the heating environment clean. |
| Data review | If the deviation of the parallel sample measurement results is too large, the sample uniformity, operation process or instrument status should be checked and re-measured. |
Routine instrument maintenance includes checking the heating element, thermocouple status, and the clearness of the exhaust channels. Before re-activating after long-term deactivation, no-load heating test and temperature distribution uniformity test should be carried out.
Cited Literature
GB/T 4498-2023 Rubber and rubber products - Determination of ash content
ASTM D5630-22 Standard Test Method for Ash in Plastic Materials
ISO 3451-1:2019 Plastics - Determination of ash - Part 1: General methods