Characterization of tire fillers with Axia ChemiSEM

Importance of the topic

Tire compounds are complex engineered composites in which the identity, amount and dispersion of fillers strongly control mechanical performance, aging and failure modes. Accurate and rapid characterization of fillers (reinforcing, semi-reinforcing and non-reinforcing) within rubber layers is therefore essential for failure analysis, quality control and formulation optimization. The ability to map elemental distributions and obtain quantitative point composition in situ accelerates root-cause investigations and supports corrective actions in manufacturing and materials selection.

Goals and overview of the study

This application note demonstrates the use of the Axia ChemiSEM platform to identify and map filler particles in a tire cross section. The aim was to show that live quantitative EDS imaging integrated with SEM imaging speeds up and simplifies: locating regions of interest, discriminating filler chemistries with similar BSE contrast, and obtaining quantitative point analyses to confirm material identity and distribution relevant to failure analysis.

Methods and analytical workflow

The workflow combined large-area SEM montage imaging for specimen navigation with higher-magnification secondary electron (SE) and backscattered electron (BSE) imaging to resolve microfeatures and particle morphology. Live quantitative elemental mapping continuously acquires and processes X-ray data during imaging, enabling on-the-fly selection of elements to visualize distributions. Targeted point analyses (30–60 s) were used to obtain quantitative atomic % values for confirmation. Typical operating conditions reported include 20 keV accelerating voltage, beam currents from ~0.48 to 0.94 nA, low-vacuum mode for large montages, and acquisition times from tens to ~100 seconds depending on ROI complexity.

Used instrumentation

• Axia ChemiSEM (SEM platform with integrated live quantitative EDS mapping)
• Conventional SEM detectors: secondary electron (topography) and backscattered electron (compositional contrast)
• Integrated EDS detector and software enabling continuous X-ray acquisition and on-screen elemental selection and mapping

Main results and discussion

• Large-area navigation montage: A 19×19 tile montage provided fast overview imaging of the tire cross section to locate tread, subtread/undertread and cap-ply regions, enabling efficient ROI selection for higher-resolution analysis.
• ZnO identification: Clusters of zinc oxide were clearly visible by BSE contrast and confirmed by live elemental maps showing Zn and O distributions. ZnO presence is consistent with its role in vulcanization and heat dissipation.
• Aluminosilicate filler: A particle near the external surface displayed Al and Si signals in a roughly 12.4 at.% Al to 6.8 at.% Si point analysis (with high O and carbon background from the matrix), consistent with an aluminosilicate (formally referred to as Al2SiO5 in the note). Quantitative maps and point spectra were produced from a single image acquisition (≈100 s).
• Calcium carbonate (CaCO3): Layered particles in subtread/undertread regions produced elemental maps dominated by Ca and O and a point analysis with comparable Ca and C and ~3× O, supporting assignment to CaCO3. CaCO3 was identified as a low-cost semi-reinforcing filler used to increase volume, hardness and abrasion/heat resistance.
• Talc (hydrous magnesium silicate): Plate-like particles with elevated Mg, Si and O signals and a measured Mg:Si atomic ratio near 3:4 were consistent with talc (Mg3Si4O10(OH)2). Talc was localized in inner layers where tear resistance and toughness are required.
• Matrix effects and spatial resolution: High acceleration voltage (20 keV) yields an interaction volume that can include signals from the rubber matrix and nearby ZnO, explaining some oxygen and minor Zn/S signals in point spectra. The integrated imaging/EDS approach allowed rapid discrimination despite these factors.

Benefits and practical applications

• Speed and simplicity: Live quantitative mapping integrated in the SEM user interface eliminates complex EDS setup and reduces time-to-result, allowing users to switch between imaging and elemental visualization with a single click.
• Comprehensive ROI characterization: Simultaneous acquisition of SE/BSE signals with continuous EDS enables correlating morphology, location within the tire structure and composition to assess dispersion and potential causes of inhomogeneity-related failures.
• Failure analysis and QC: The approach supports routine failure investigations, production troubleshooting and formulation verification by quickly identifying improper filler types, agglomeration, or uneven distribution across layers.

Future trends and potential uses

• Lower-voltage mapping and improved spatial resolution: Adapting beam energy and detector geometries to reduce interaction volume could improve phase separation for sub-micron fillers and decrease matrix contribution to spectra.
• Automated defect classification: Combining live elemental maps with machine learning could enable automated detection of filler agglomerates, segregation and anomalies across large montages for high-throughput QC.
• Multi-modal correlative analysis: Integration with Raman, FTIR or micro-tomography could provide polymer-phase identification and 3D filler distribution, enhancing root-cause analysis for complex tire failures.
• Real-time production feedback: Faster, user-friendly SEM-EDS can be deployed closer to process control to monitor batch-to-batch consistency and support rapid corrective actions in manufacturing.

Conclusions

Live quantitative EDS mapping within the Axia ChemiSEM platform streamlines identification and spatial mapping of common tire fillers (ZnO, aluminosilicates, CaCO3, talc) directly during SEM imaging. The combined imaging and on-the-fly elemental quantification reduces setup complexity and acquisition time, improves detection of compositionally similar particles that cannot be resolved by BSE alone, and thus provides an efficient workflow for failure analysis and quality control in tire materials characterization.

Reference

• Brewer HK. The Pneumatic Tire. U.S. Department of Transportation, National Highway Traffic Safety Administration, 2006.
• Roy K. A critical review on the utilization of various reinforcement modifiers in filled rubber composites. Journal of Elastomers & Plastics. 2019;52(2):167–193. doi:10.1177/0095244319835869