Analysis of Rubber by Evolved Gas Analysis Method

Significance of the topic

Rubber materials are central to applications ranging from automotive components to consumer goods. Understanding their composition and thermal behavior is crucial for optimizing performance, ensuring quality control, and developing new formulations. Evolved Gas Analysis (EGA) coupled with GC/MS enables temperature‐resolved detection of decomposition products and additives, offering a detailed profile of polymer and additive content.

Objectives and Study Overview

This study aimed to compare two natural rubber samples, designated A and B, by applying EGA‐GC/MS and thermal desorption GC/MS. Key goals included identifying temperature‐dependent evolution of gases to guide desorption temperature selection and characterizing additives, plasticizers, and vulcanizing agents present in the materials.

Methodology and Used Instrumentation

The experimental workflow consisted of two complementary approaches:

• Evolved Gas Analysis (EGA): A single‐shot pyrolysis system heated samples from 50 °C to 500 °C at 10 °C/min. The generated gases were introduced directly into a GCMS‐QP2010 for mass spectrometric detection.
• Thermal Desorption GC/MS: Based on EGA findings, a desorption temperature of 300 °C was selected. Evolved compounds were separated on a DB‐5ms capillary column and analyzed by GCMS under helium carrier gas.

Used Instrumentation:

• GCMS-QP2010 mass spectrometer
• PY-2020D pyrolyzer (Frontier Laboratories)
• Column: UADTM-2.5N (2.5 m × 1.5 mm ID) for EGA; DB-5ms (30 m × 0.25 mm ID, df 0.25 μm) for desorption
• Carrier gas: helium

Main Results and Discussion

EGA curves for both samples exhibited two major peaks (P-1, P-2). Mass spectra interpretation suggested:

• P-1 corresponds to an antioxidant (NOCRAC 6C, m/z 211, 268).
• P-2 corresponds to cycloparaffinic hydrocarbons (m/z 41, 43, 55, 69).

The thermal desorption GC/MS at 300 °C revealed multiple components:

1. Aniline (potential processing aid)
2. C16 and C18 fatty acids (vulcanizing agents)
3. Antioxidants NOCRAC 810-NA and NOCRAC 6C
4. N-alkanes from C24 to C32 (softening agents)

Comparison showed Sample A contained a higher abundance of long‐chain hydrocarbons, while Sample B exhibited reduced hydrocarbon peaks, indicating formulation differences. Temperature‐resolved ion monitoring demonstrated the onset temperatures for antioxidants, fatty acids, and hydrocarbons, guiding optimal desorption settings.

Benefits and Practical Applications

The combined EGA and thermal desorption approach offers:

• Rapid selection of desorption temperature based on comprehensive thermal profiles
• Simultaneous detection of polymers, additives, and softeners in a single run
• Enhanced quality control by detecting formulation variations between batches
• Insight into thermal stability and degradation behavior essential for material development

Future Trends and Possibilities

Advances may include coupling EGA‐GC/MS with automated data analysis and chemometric models for high‐throughput screening. Integration with advanced detectors such as time‐of‐flight MS or infrared sensors could improve sensitivity and compound identification. Online EGA platforms may enable real‐time monitoring of polymer processing and recycling streams.

Conclusion

This application of EGA and thermal desorption GC/MS provides a robust framework for detailed rubber analysis. Temperature‐resolved gas profiling guides desorption settings and delivers comprehensive additive characterization, supporting quality assurance and formulation optimization in rubber production.