Introduction
In the research and production process of rubber materials, the accurate determination of carbon black content is of great significance for evaluating material properties, optimizing formulations, and controlling quality. As an analytical technique based on mass change, thermogravimetric analysis can realize the quantitative analysis of carbon black content in rubber through the relationship between sample mass and temperature or time under programmed temperature control conditions. This method has the characteristics of easy operation, reliable results and wide range of application, and has been widely used in the rubber industry and related fields.
Principle overview
The basic principle of thermogravimetric analyzers is to measure the change in the mass of a sample with temperature or time under a controlled temperature program. For rubber samples, heating in an inert atmosphere (such as nitrogen) breaks down the rubber polymer and volatilizes it, while carbon black remains stable in an inert atmosphere. By switching to an oxidizing atmosphere (such as air or oxygen), the carbon black is oxidized and decomposed, thus the carbon black content is calculated by mass loss. The entire process can be carried out according to relevant standard methods to ensure data comparability and accuracy.
The initial mass of the sample is set to m0, the remaining mass after decomposition in an inert atmosphere is m1(mainly carbon black and inorganic fillers), and the remaining mass after decomposition in the oxidizing atmosphere is m2(mainly inorganic ash). Then the carbon black content is CCBIt can be calculated by the following formula:
CCB = (m1 - m2) / m0 × 100%
Experimental methods
Sample preparation needs to be representative, usually cutting or grinding rubber samples into uniform pieces or particles, with a generally recommended quality between 10 and 20 mg. The instrument parameters include the heating rate, atmosphere switching point and final temperature. The typical procedure is to heat up at a constant rate in a nitrogen atmosphere until the polymer is completely decomposed (e.g., 600°C), switch to an oxygen or air atmosphere, and continue to heat until the carbon black is fully oxidized (e.g., 800°C). During the experiment, attention should be paid to baseline correction and buoyancy effect compensation.
| Steps | Key parameters: |
| Sample preparation | Homogeneous granules, mass 10-20mg |
| Atmosphere control | Nitrogen to 600°C, switching oxygen to 800°C |
| Rate of warming | 10-20°C/min |
| Data logging | Continuous monitoring of quality changes |
Influencing factors
The accuracy of the analysis results is influenced by several factors. Insufficient sample uniformity may lead to data bias; Too fast heating rate may overlap the decomposition intervals and affect the resolution. The purity of the atmosphere and the timing of switching had an impact on the judgment of the starting point of carbon black oxidation. In addition, the decomposition behavior of other components in rubber (e.g., plasticizers, inorganic fillers) needs to be considered in the analysis. Improve the reliability of your results by optimizing experimental conditions and performing repeated tests.
Application examples
Taking a synthetic rubber as an example, the above method is used for testing. In a nitrogen atmosphere, polymer decomposition leads to a mass loss of about 65%; After switching to oxygen, carbon black oxidation led to a further mass loss of about 25%; The final remaining mass is about 10% inorganic ash. The calculated carbon black content is about 25%, which is basically consistent with the theoretical formula. This result can be used to guide production process adjustments or material property evaluation.
Summary
Thermogravimetric analyzer provides an effective means for the quantitative determination of carbon black content in rubber. Through standardized experimental procedures and rigorous data processing, accurate and reproducible analysis results can be obtained. In practical applications, optimizing method parameters based on specific material properties can help better serve the research and development and quality control of rubber materials.
References
1. Thermal Analysis in Polymeric Materials, Journal of Materials Testing Technology, 2020.
2. Standard Methods for Quantitative Analysis of Rubber Components, International Standards Organization, 2018.
3. Progress in thermogravimetric analysis, Journal of Analytical Instruments, 2021.