Determination of the Cross-linking Agent in Cross-linked Polycarbonate by Reactive Pyrolysis GC/MS

Significance of the Topic

Cross-linking agents such as 1,1,1-tris(p-hydroxyphenyl)ethane (THPE) are used to fine-tune the melt viscosity of polycarbonate. Determining the precise concentration of THPE incorporated into the polymer backbone is crucial for controlling material properties and ensuring consistent performance in molding and recycled applications.

Objectives and Study Overview

This study aims to develop a rapid, simple and quantitative method for measuring THPE content in cross-linked polycarbonate. The approach replaces conventional hydrolysis and solvent extraction steps with reactive pyrolysis coupled to gas chromatography.

Methodology and Used Instrumentation

The analytical workflow involves:

• Sample preparation: dissolving cross-linked polycarbonate in dichloromethane and depositing on a deactivated sample cup.
• Derivatization: adding tetramethyl ammonium hydroxide (TMAH) methanol solution directly in the pyrolyzer cup.
• Reactive pyrolysis: heating the sample at 400°C in a double-shot pyrolyzer model 2020iD interfaced to a split/splitless GC-FID.
• Chromatographic conditions: Ultra ALLOY-5 column, He carrier gas, split ratio 1:200, oven ramp from 200°C to 320°C at 5°C/min.

Main Results and Discussion

Reactive pyrolysis generates two key methylated products: dimethyl bisphenol A (Me-BisA) from the polymer backbone and trimethyl THPE (Me-THPE) from the cross-linker. Quantification using peak-area ratios indicates a THPE content of approximately 0.4 weight percent in the sample. Method reproducibility was excellent, with a relative standard deviation of 1.2% over five replicates.

Benefits and Practical Applications

The proposed method offers significant advantages over traditional approaches:

• Streamlined workflow with no need for time-intensive hydrolysis or liquid–liquid extraction.
• Improved data quality and reproducibility suitable for QA/QC and research laboratories.
• Potential for rapid screening of cross-linked polymers and recycled materials.

Future Trends and Applications

Advances may include coupling reactive pyrolysis to mass spectrometry for enhanced specificity, applying the technique to other polymer matrices and cross-linking agents, and integrating high-throughput automation for industrial quality control.

Conclusion

This work demonstrates a robust, quantitative reactive pyrolysis GC method for determining THPE in cross-linked polycarbonate. The approach reduces sample preparation, accelerates analysis and delivers reliable results, supporting optimized polymer processing and recycling strategies.

References

1. K. Odagiri et al. Presentation at the 12th Polymer Analysis & Characterization Japan 2007, IV-15.