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Real-Time Mapping of Polymer Film Thickness Using Near-Infrared Hyperspectral Imaging.
Xiaoyun Chen1, Jin Wang2, Christopher Thurber2
1Analytical Science, 1897 Building, The Dow Chemical Company, Midland, Michigan 48667, USA.
Applied Spectroscopy
|March 13, 2025
Summary
A novel near-infrared (NIR) hyperspectral imaging (HSI) method enables real-time, 2D polymer film thickness mapping. This advanced technique offers superior line-based measurements compared to traditional point-based methods.
Area of Science:
- Materials Science
- Spectroscopy
- Polymer Engineering
Background:
- Traditional polymer film thickness measurement methods (X-ray, capacitance, physical gauging) are limited to point measurements.
- Online monitoring of film thickness is crucial for quality control in polymer manufacturing.
- Existing methods lack the capability for comprehensive, real-time thickness distribution analysis.
Purpose of the Study:
- To develop and validate a new online method for polymer film thickness mapping using near-infrared hyperspectral imaging (NIR-HSI).
- To enable true real-time two-dimensional (2D) thickness profiling of polymer films.
- To compare the performance of the NIR-HSI method with existing industrial thickness measurement techniques.
Main Methods:
- Utilized a Specim NIR camera (1000-2500 nm) for hyperspectral data acquisition of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) films.
- Employed the 2310 nm NIR absorbance peak as the primary feature for quantitative thickness determination across a range of 10–100 μm.
- Applied classical least squares (CLS) analysis to mitigate interference fringes, a common error source in thin film analysis.
Main Results:
- Demonstrated the capability of NIR-HSI to map polymer film thickness with line-based measurements, enabling 2D profiling.
- Established a strong correlation between 2310 nm absorbance and film thickness, consistent with X-ray thickness scanner results.
- Successfully implemented the NIR-HSI method for real-time thickness mapping in an industrial blown film process.
Conclusions:
- NIR-HSI provides an effective, non-contact method for real-time, 2D polymer film thickness mapping.
- The 2310 nm absorbance feature and CLS analysis are key components for accurate quantitative measurements.
- This technology offers significant advantages over traditional point-based methods for online quality control in polymer film production.
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