Multi-Step Analysis of Automobile Tire Rubber

Importance of the Topic

Automobile tire rubber is a complex material composed of natural and synthetic polymers, carbon black, oils and various additives. Comprehensive analysis of these components is essential for product development, quality control, regulatory compliance and end-of-life recycling processes. A targeted analytical approach enables accurate identification of contaminants, additives and polymer composition in tire samples.

Objectives and Study Overview

This study presents a multi-step temperature programming method using pyrolysis-gas chromatography to selectively analyze volatile contaminants, semi-volatile additives and polymer constituents in tire rubber. The approach aims to simplify chromatograms, improve detection of minor components and provide clear identification of polymer monomers.

Methodology

The analytical sequence consists of three thermal steps:

• Initial heating at 150 °C to remove low-boiling volatiles and environmental contaminants.
• Intermediate heating at 300 °C to vaporize inherent additives such as hydrocarbon oils and antioxidants.
• High-temperature pyrolysis at 700 °C to cleave the polymer backbone, releasing monomeric and dimeric fragments for identification.

Used Instrumentation

Pyrolyzer: CDS Pyrolyzer 6200 with Pyroprobe interface
• Temperature program: 150 °C for 20 s, 300 °C for 15 s, 700 °C for 10 s
• Interface and valve oven held at 300 °C, transfer line at 315 °C

GC–MS conditions:
• Column: 30 m × 0.25 mm, 5 % phenyl methyl siloxane
• Carrier gas: Helium, split ratio 100:1
• Oven: 40 °C hold 2 min, ramp 10 °C/min to 325 °C

Key Results and Discussion

The low-temperature step effectively removed environmental volatiles, eliminating interference in subsequent analyses. The 300 °C phase revealed a broad hydrocarbon oil peak (20–30 min) and a distinct antioxidant 6-PPD peak at ~27 min. The final pyrolysis at 700 °C produced a simplified pyrogram dominated by butadiene-isoprene monomer and dimer fragments, confirming the rubber polymer type.

Benefits and Practical Applications

• Enhanced selectivity by isolating contaminant, additive and polymer signals
• Improved chromatographic clarity and peak resolution
• Rapid identification of polymer composition for QA/QC and forensic analysis
• Minimal sample preparation with automated thermal sequencing

Future Trends and Potential Applications

• Integration with high-resolution mass spectrometry for detailed structural elucidation
• Automated data processing and chemometric analysis for pattern recognition
• Extension to other rubber products and recycled tire materials
• Development of standardized protocols for regulatory and environmental studies

Conclusion

The multi-step pyrolysis-GC method offers a robust tool for comprehensive profiling of tire rubber, enabling sequential removal and analysis of volatiles, additives and polymers. This approach improves analytical specificity, streamlines workflows and supports diverse applications in quality control, materials research and forensic investigations.