Calcium carbonate (CaCO₃) is one of the most commonly used fillers in PVC products. In industrial production, manufacturers often adjust the CaCO₃ ratio to reduce costs, improve rigidity, and optimize processing performance.

Because different PVC formulations usually contain different filler ratios, calcium carbonate analysis is also important in material identification, quality control, and forensic investigations involving plastic samples.

Among the available testing technologies, Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) and Fourier Transform Infrared Spectroscopy (FT-IR) are two widely used methods for determining CaCO₃ content in PVC materials.

1. SEM-EDS Analysis

Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) is mainly used for microscopic elemental analysis.

PVC contains chlorine (Cl), while calcium carbonate contains calcium (Ca). By measuring the relative proportion of Ca and Cl elements in the sample, technicians can estimate the calcium carbonate filler content through calibration data.

Advantages of SEM-EDS

• Requires only a very small sample amount

• Suitable for tiny plastic fragments and trace samples

• High sensitivity for micro-area analysis

• Useful for forensic and failure analysis applications

Limitations of SEM-EDS

SEM-EDS results can be influenced by the thermal history of the sample.

If PVC materials have experienced burning or prolonged high-temperature exposure, chlorine may partially escape from the material as HCl gas. This changes the Ca/Cl ratio and may lead to inaccurate results.

For this reason, severely heat-damaged PVC samples are generally not recommended for SEM-EDS quantitative analysis.

2. FT-IR Analysis

Fourier Transform Infrared Spectroscopy (FT-IR) is a mature non-destructive material analysis method widely used in laboratories and industrial quality control.

Calcium carbonate produces characteristic absorption peaks in the infrared spectrum. By analyzing these peaks and comparing them with calibration standards, the CaCO₃ concentration in PVC can be estimated.

Advantages of FT-IR

• Non-destructive testing method

• Fast and stable analysis process

• Mature and widely available technology

• Suitable for routine quality control

FT-IR is commonly preferred when the sample needs to remain intact or when sufficient material is available for standard testing procedures.

SEM-EDS vs. FT-IR

Both methods have their own advantages depending on the testing objective and sample condition.

In many practical applications, laboratories combine SEM-EDS and FT-IR to cross-check data and improve analytical reliability.

As PVC formulations continue evolving in industries such as cable, pipe, flooring, and construction materials, accurate calcium carbonate filler analysis remains an important part of product quality control and material identification.

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