Thermogravimetric analysis of thermal stability of polyvinyl chloride resin

Polyvinyl chloride (PVC) resin, as the core variety of general-purpose plastics, is widely used in key fields such as building pipes, electronic and electrical insulation, packaging materials, etc. Its thermal stability directly determines the feasibility of product processing and service safety. During high-temperature processing or long-term use, PVC is prone to dehydrochlorination chain degradation, leading to material discoloration, brittleness, and even failure. Therefore, accurately characterizing the thermal degradation behavior has become a core requirement for formula optimization and quality control.

Thermogravimetric AnalyzerReal time monitoring of the quality changes of PVC under programmed heating can provide key parameters such as initial decomposition temperature and high degradation rate, providing scientific basis for PVC resin research and development, stabilizer screening, and production process quality control.

1、 Experimental operation steps

1. Measuring instrument: DZ-TGA201 thermogravimetric analyzer

2. Sample preparation process: This experiment focuses on optimizing TGA testing conditions and analyzing thermal degradation behavior of industrial grade PVC resin

2.1 Pre treatment: Place the PVC resin in an 80 ° C drying oven and dry for 4 hours to remove any moisture interference.

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

2.3 Sample dosage: Weigh 10-20mg of the sample and place it in a ceramic crucible. If the sample quantity is too large, it will cause uneven heat transfer, while if it is too small, it will cause weak signals and affect data accuracy;

3. Set software parameters: Set temperature, heating rate, and atmosphere environment through device operation software. End temperature: 700 ° C, heating rate of 20 ° C/min, full nitrogen atmosphere throughout the process.

4. Measurement spectrum analysis:

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

1. Hydrochlorination stage (200-350 ℃): Unstable chlorine atoms on the PVC molecular chain trigger a chain reaction, releasing HCl gas and forming conjugated polyene structures. The mass loss in this stage accounts for about 70% of the total mass.

2. Main chain breakage stage (300-700 ℃): The conjugated polyene structure further decomposes into low molecular weight hydrocarbon compounds, and the residue eventually forms carbonaceous residue.

The first stage DTG peak (around 300 ℃) confirms the concentrated occurrence of HCl removal reaction, and the characteristic absorption peak of HCl can be detected by infrared spectroscopy; The broadening of peak shape in the second stage indicates that the carbon chain degradation reaction is more complex. And from this figure, we can also obtain the initial decomposition temperature of the PVC sample, which is Toneset equal to 246.83 ℃. The peak value of the DTG curve corresponds to the maximum degradation rate Tmax at each stage, and the maximum decomposition rate temperature is 303 ℃.

2、 Experimental conclusion

Thermogravimetric analysis, as the core technology for evaluating the thermal stability of PVC resin, can quantitatively characterize the degradation stage, heat resistance level, and reaction mechanism by accurately analyzing the characteristic parameters of TG-DTG curve. It effectively distinguishes the differences in thermal stability of different formulations of PVC. Even for resins with similar appearances, thermogravimetric analyzers can identify subtle differences through parameters such as initial decomposition temperature and maximum decomposition rate temperature, providing key support for production consistency and reliability control. By combining thermogravimetric analysis with infrared or mass spectrometry, the chemical mechanism of PVC degradation can be further revealed, providing a microscopic basis for the design of stabilizer molecules.