Pyrolysis of Rubber with Antioxidant 6-PPD - JSB

Importance of the Topic

Characterization of complex polymer materials such as tire rubber and conductive inks is essential for performance evaluation, formulation optimization and patent analysis. Rapid analytical methods that deliver detailed compositional information support quality control, regulatory compliance and competitive intelligence in materials development.

Objectives and Study Overview

This study presents two case applications:

• Pyrolysis of automobile tire rubber containing antioxidant 6 PPD to determine polymer monomer composition, antioxidant identity and added hydrocarbon oil fractions in a single run.
• Hyphenated gel permeation chromatography infrared spectroscopy de formulation of a silver ink paste to separate three polymeric components and identify their chemical structure and supplier origin.

Methodology and Instrumentation

• Pyroprobe GC MS analysis of tire sample. A 100 microgram piece of rubber was placed in a quartz tube in the coil filament of a CDS Pyroprobe 2000 interfaced via a Model 1500 valved interface at 300 C to an Agilent 6890 gas chromatograph column HP 5 coupled to a 5973 MSD detector. Pyrolysis was performed at 700 C for 10 seconds with a heating rate of 10 C per millisecond.
• GPC IR analysis of silver ink paste. Gel permeation chromatography was performed on a hyphenated IR system such as a DiscoVIR LC instrument. Helium carrier gas with a 50 to 1 split ratio was used and separation was achieved on a suitable column. Infrared spectra were captured over the full FTIR range for each separated fraction and matched against an IR database for component identification.

Main Results and Discussion

• Pyrolysis of tire rubber at 700 C yielded early peaks corresponding to butadiene and isoprene monomers and dimers from the polymer matrix, a distinct peak for antioxidant 6 PPD confirmed by mass spectrum at m z 268, and a region of unresolved hydrocarbon oil peaks at the end of the pyrogram. This single analysis provided comprehensive data on the rubber copolymer composition, antioxidant type and oil additive.
• GPC IR separation of the silver ink paste revealed three polymeric components. Component A was identified as an aliphatic polyester resin with high molecular weight broad distribution used for flexible adhesion. Component B was an aliphatic polyurethane grade with medium molecular weight narrow distribution ideal for elastomeric cross linking. Component C was a ketoxime blocked HDI trimer latent cross linking agent stable at room temperature and activated at elevated temperature. Supplier origins were assigned by matching IR bands to reference spectra.

Benefits and Practical Applications

These analytical approaches enable rapid de formulation of complex polymer blends in a single workflow. Py GC MS informs tire compound design by detailing monomer ratios, antioxidant levels and oil content. GPC IR de formulation supports ink and coating developers in understanding polymer architecture, additive identity and sourcing without extensive manual separation. Both methods strengthen quality assurance, accelerate formulation development and guide intellectual property analysis.

Future Trends and Possible Applications

Advances in pyrolysis pyroprobe design and coupling with high resolution MS will enhance sensitivity for trace additives and cross linked polymers. Integrated GPC IR instruments with machine learning based spectral matching will allow fully automated de formulation and real time feedback. The expansion of hyphenated chromatography infrared methods to online reaction monitoring and polymer aging studies will further broaden applications in materials science and industrial analytics.

Conclusion

Pyrolysis GC MS and GPC IR are powerful complementary techniques for comprehensive characterization of polymer formulations. Single run analysis of complex materials delivers actionable data on polymer composition, additive identity and functional performance. Adoption of these methods enhances formulation development, quality control and competitive intelligence in the polymer and materials industry.

Reference

• T P Wampler LC GC 17 1999 S14