Profiling Analysis of Polysulfide Silane Coupling Agent

Significance of the Topic

In modern tire manufacturing, silica is used as a reinforcing filler to improve mechanical strength and reduce reliance on petroleum-based materials.
However, its hydrophilic surface impairs bonding with lipophilic elastomers, causing poor processibility and compromised tire performance.
Polysulfide silane coupling agents address this by forming durable bridges between silica and rubber, enhancing adhesion, processibility, and mechanical properties.

Objectives and Overview of the Study

This study aimed to differentiate four commercial Bis(triethoxysilylpropyl) polysulfide (TESPP) coupling agents from distinct manufacturers despite sharing an identical core structure.
The goal was to identify marker molecules and compositional variances using high-resolution mass spectrometry combined with multivariate statistical analysis.

Methodology and Instrumentation

Four TESPP samples were diluted in methanol (1:10000), with a pooled QC sample prepared for repeatability checks.
Analyses were performed in triplicate on an LCMS-IT-TOF system using gradient elution on a Shim-pack XR-ODS column (75×2.0 mm, 2.2 µm) with ammonium formate and acetonitrile.
Profiling Solution software executed retention time alignment and peak picking to generate a data matrix.
PCA was conducted in SIMCA-P to visualize sample clustering, and marker ions were characterized via MSn and Formula Predictor.

Used Instrumentation

• Shimadzu LCMS-IT-TOF high-performance liquid chromatograph/ion trap time-of-flight mass spectrometer
• Shim-pack XR-ODS column (75 mm×2.0 mm I.D., 2.2 µm)
• Profiling Solution retention time alignment and data processing software
• SIMCA-P multivariate analysis package
• Formula Predictor formula prediction tool

Main Results and Discussion

Total ion chromatograms for samples A and B were highly similar, while sample D exhibited a distinct profile dominated by monosulfide (TESPM) rather than higher polysulfides.
PCA score plots clustered A and B together, separated sample C, and isolated D; loadings identified m/z 323, 397, 465 as markers for D and m/z 510, 542 for C.
MSn fragmentation confirmed the presence of TESPT (trisulfide) in A–C and TESPM (monosulfide) uniquely in D.
Additional minor polysulfide and contaminant peaks varied by manufacturer, reflecting differences in synthesis or purity.

Benefits and Practical Applications

This integrated profiling and multivariate workflow offers a robust fingerprinting method for silane coupling agents, enabling rapid supplier differentiation and quality control.
Such capabilities support tire formulators in raw material selection and QC laboratories in verifying batch consistency.

Future Trends and Potential Uses

Emerging high-throughput profiling, AI-augmented statistical analysis, and expanded MSn databases will enhance detection of trace impurities.
Integration with real-time monitoring and sustainable synthesis analytics promises on-line QC and greener coupling agent development.

Conclusion

The combination of LCMS-IT-TOF and multivariate analysis effectively distinguished polysulfide silane coupling agents from different sources and identified characteristic marker ions.
This approach strengthens QC protocols and deepens insight into structure–performance relationships in silica-reinforced rubber systems.

References

• Shimadzu Technical Report C146-E154A: Profiling Analysis of Polysulfide Silane Coupling Agent, Shimadzu Corporation, 2010/2012.