Thermogravimetric Analyzer for Determining the Solid Content of Coatings

Thermogravimetric analyzers determine the solid content of coatings by monitoring the change in sample mass with temperature, offering faster and more precise results compared to traditional oven methods. During the measurement, the sample is heated in an inert atmosphere, and the mass remaining after volatile components evaporate represents the solid components. The solid content is then calculated using a formula. Typical conditions include a heating rate of 10°C/min, a temperature up to 600°C, and a nitrogen atmosphere. Attention must be paid to sample uniformity and heating rate control during operation. This method is suitable for various types of coatings, features a high degree of automation, and is applicable for both research and quality control purposes.

Overview

The solid content of coatings is one of the key parameters for evaluating the performance of coatings, which directly affects the mechanical properties, durability and construction efficiency of coatings. Traditional measurement methods such as the oven method are easy to operate, but they are time-consuming and can have additional effects on temperature-sensitive components. By monitoring the change of sample quality with temperature or time, thermogravimetric analyzers can quickly and accurately determine the solid content of coatings, especially suitable for R&D and quality control processes.

Principle of determination

Based on the principle of conservation of mass, the thermogravimetric analyzer records the changes in sample quality in real time under the condition of program temperature control. After the paint sample is heated, volatile components (such as moisture, solvents) gradually escape, and the remaining mass is the solid component. The solid content can be calculated by the following formula:

Solid content (%) = (W_f / W_i) × 100

Among them, W_iis the initial mass, W_ffor the final quality. The assay is usually performed in an inert atmosphere to avoid oxidative reaction interference.

Instruments and conditions

Thermogravimetric analyzers need to have a highly sensitive balance and a precise temperature control system. Typical assay conditions are as follows: The temperature ramp rate is typically 10°C/min, the temperature range is from room temperature to 600°C, the atmosphere is nitrogen or argon, and the flow rate is about 50 mL/min. The recommended sample size is 5-20 mg, evenly tiled in a crucible to ensure consistent heat transfer.

Parameters	Typical setup
Rate of warming	10°C/min
Temperature range	Room temperature to 600°C
Atmosphere	Nitrogen
Sample volume	5-20 mg

Procedure:

Start by calibrating the instrument to ensure accurate balance and temperature readings. Representative paint samples are taken and placed in a crucible to record the initial quality. Place the crucible in a thermogravimetric analyzer and heat up according to the set program. Monitor the quality change curve in real time and record the final quality when the quality no longer degrades. The solids content is calculated by formula, and the assay is repeated to verify repeatability.

Notes:

Sample uniformity, temperature rise rate, and atmosphere type can all affect the results. The uneven sample is easy to cause local overheating, and the volatile content may not completely escape if the temperature rises too quickly. Method optimization is recommended, such as determining the appropriate temperature range through pre-experiments. In addition, the instrument should be cleaned regularly to avoid residue interference.

Influencing factors	Control measures
Sample uniformity	Stir well and then sample
Rate of warming	Optimized to 5-20°C/min
Atmosphere purity	Use high-purity inert gas

Application:

This method is suitable for a wide range of coatings, including water-based, solvent-based, and powder coatings. Thermogravimetric analyzers provide more comprehensive thermal decomposition information than traditional methods, which can help analyze component composition. It has a high degree of automation and strong data traceability, making it suitable for batch testing.

References

International standard ISO 11358-1:2022, General principles for thermogravimetric analysis of plastics.

Chinese National Standard GB/T 27761-2011, Determination method of weight loss and residual amount of thermogravimetric analyzer.

Paint Testing Technology Handbook, Chemical Industry Press, 2019.