Analysis of Inorganic Additives in Resin by FTIR and EDX

Significance of the Topic

Inorganic additives play a critical role in enhancing the functionality, stability and workability of various materials across industries such as plastics, electronics and pharmaceuticals. Accurate identification and quantification of these additives are essential for quality control, product development and regulatory compliance.

Objectives and Study Overview

This study demonstrates the application of Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDX) for the analysis of common inorganic additives in both pure form and within a resin matrix. Four representative additives — aluminum silicate, aluminum hydroxide, magnesium silicate, and calcium carbonate — are characterized by FTIR, followed by combined FTIR/EDX analysis of an actual connector cover sample.

Methodology

Pure additive samples were examined by attenuated total reflection FTIR using a diamond prism. A connector cover containing an inorganic filler was analyzed by both FTIR and EDX to resolve compositional ambiguities. FTIR spectra were matched against a standard library. EDX provided elemental and compound quantification.

Used Instrumentation

• FTIR: IR Tracer-100 with Quest accessory and diamond ATR prism; 4 cm-1 resolution; 40 scans; Happ-Genzel apodization; DLATGS detector.
• EDX: EDX-7000 with Rh X-ray tube; 15 kV for Na-Sc and 50 kV for Ti-U; vacuum atmosphere; 10 mm measurement diameter; 100 s integration time.

Main Results and Discussion

FTIR analysis of pure additives revealed broad absorption bands at low wavenumbers and characteristic peaks at higher wavenumbers, enabling identification of each compound:

• Aluminum silicate: diagnostic peaks corresponding to Si-O vibrations.
• Aluminum hydroxide: distinct OH stretching modes.
• Magnesium silicate: combined Si-O and OH features.
• Calcium carbonate: strong peak near 1390 cm-1.

Connector cover FTIR spectra matched polyvinyl chloride and showed a shifted carbonate peak at approximately 1415 cm-1, suggesting filler presence but ambiguous assignment from FTIR alone. EDX qualitative results identified chlorine and calcium as major elements. Quantitative EDX confirmed about 26% Ca and 72% Cl by weight. Compound quantification indicated CaCO3 and PVC matrix along with minor oxide components, conclusively verifying calcium carbonate as the inorganic additive.

Benefits and Practical Application

The integrated FTIR/EDX approach offers robust qualitative and quantitative insights into additive composition without extensive sample preparation. This methodology supports contaminant analysis, compliance testing and material verification in electrical, chemical, pharmaceutical and food industries.

Future Trends and Possible Applications

Emerging directions include micro-FTIR imaging, automated spectral deconvolution, combined XRF-FTIR platforms and machine learning based library searches. These advancements promise higher throughput, enhanced sensitivity and greater analytical depth for additive characterization.

Conclusion

The combined use of FTIR and EDX enables clear identification and quantification of inorganic additives within complex matrices. This synergy enhances confidence in additive analysis for research, development and quality control applications.

Reference

1. Toshikatsu Nishioka, Tatsuya Housaki. A Guide on Plastic Analysis. Maruzen Publishing Co., Ltd., 2011.
2. Hirotomo Ochi, Hideo Okashita. Shimadzu Review, 45(1-2):51, 1988.
3. Sachio Murakami et al. Shimadzu Review, 69(1-2):133, 2012.