Thermogravimetric analysis of epoxy anti-corrosion coatings using a thermogravimetric analyzer

Epoxy anti-corrosion materials have become the core protective materials in corrosive environments such as petrochemicals, marine engineering, and bridge infrastructure due to their excellent adhesion, chemical inertness, and mechanical strength. Their long-term service stability directly determines the service life and safe operation of the protected substrate. Under complex working conditions such as high temperature, humidity, and chemical media, epoxy materials are prone to curing cross-linking failure, molecular chain degradation, and other problems, resulting in coating foaming, peeling, and loss of protective function. Thermogravimetric analysis (TGA), as a key technology for quantifying the thermal properties of materials, has advantages such as high sensitivity, dynamic monitoring, and objective data. It can capture the quality changes of epoxy anti-corrosion materials in real-time during the programmed heating process, accurately obtain thermal degradation characteristic parameters, and provide scientific basis for material formulation optimization, construction process improvement, and service life evaluation.

1、 Operation steps of the experiment

1. Experimental equipment:DZ-TGA201 Thermogravimetric Analyzer

2. Sample preparation process: This experiment focuses on optimizing TGA testing conditions and analyzing thermal degradation behavior of industrial grade epoxy anti-corrosion coatings (after curing).

2.1 Pre treatment: Place the cured epoxy coating sample in an 80 ℃ drying oven for 4 hours to thoroughly remove adsorbed moisture and residual small molecule solvents, avoiding interference with test results;

2.2 Preparation method: Use a grinding machine to crush the sample, sieve it to ensure uniform particle size.

2.3 Sample Dosage: Use a ceramic crucible as the sample container, accurately weigh 15 ± 2mg of the sample and place it in the crucible. Excessive sample size can lead to uneven internal heat transfer, temperature gradients, and affect the determination of degradation rate; If the sample size is too small, the signal will be weak and the accuracy of the data will be reduced.

3. Set software parameters: Set temperature, heating rate, and atmosphere environment through device operation software.

End temperature: 800 ° C, heating rate of 20 ° C/min, full nitrogen atmosphere throughout the process.

4. Measurement chart:

5. Measurement spectrum analysis:

From the data in the above figure, we can see that the thermal degradation of epoxy resin under nitrogen atmosphere exhibits a typical three-stage characteristic

5.1 Stage 1 (200-350 ℃): During this stage, the mass loss accounts for 3-5% of the total mass, mainly due to the volatilization process of residual trace moisture, incompletely cured epoxy monomers, and small molecule additives in the sample. The DTG curve has no obvious peak in this interval, indicating that the reaction is gentle at this stage and belongs to the physical volatilization process.

5.2 Second stage (350-600 ℃): This stage is the main degradation stage, with mass loss accounting for 40-50% of the total mass, corresponding to the strong sharp peak of the DTG curve, with a Tmax of 465.94 ℃. This stage mainly involves the breakage of ether bonds, ester bonds, and other small molecule degradation products such as phenol and formaldehyde on the molecular chain of epoxy materials, while the cross-linking structure gradually disintegrates. It is the core evaluation range for the thermal stability of materials.

5.3 Third stage (650-800 ℃): Based on material differences, the mass loss in this stage accounts for about 5% of the total mass, and the DTG curve shows a broad and gentle peak with a Tmax of 620.8 ℃. The main cause is the further cracking of incomplete carbides formed in the previous stage, releasing low-carbon hydrocarbon compounds. The final residue is stable carbonaceous residue, with a residual amount of about 35-40%.

The key thermal performance parameters of the epoxy anti-corrosion material can be obtained through curve analysis: the initial decomposition temperature (Tonset) is 256.84 ℃, the maximum decomposition rate temperature is 465.94 ℃ (main degradation stage), and the residual amount is 45% at 800 ℃. Among them, Tonset and Tmax in the main degradation stage directly reflect the material's tolerance to high temperature environments, while the residual amount is related to the material's carbon forming flame retardant performance and long-term anti-corrosion potential.

2、 Conclusion of the experiment

This DZ-TGG201 thermogravimetric analyzer has a combination technology that can simultaneously detect small molecule products released during thermal degradation, reveal degradation reaction mechanisms, and provide scientific support at the micro level for the optimization of epoxy anti-corrosion material formulations (such as stabilizer selection, crosslinking agent ratio adjustment) and modification technology research and development (such as nano filler composite, flame retardant modification). In the future, with the continuous upgrading of testing technology, TGA will play a more important role in predicting the long-term service life of epoxy anti-corrosion materials, evaluating their adaptability to harsh environments, and promoting the development of the anti-corrosion material industry towards high performance and high reliability.