Deterioration Analysis of Automobile Headlight Cover by Plastic Analyzer

Significance of the Topic

FTIR spectroscopic analysis is a key approach for assessing the degradation of plastic components in automotive applications. Over time, exposure to heat and UV light causes discoloration, embrittlement and chemical alterations that impact performance and safety. Rapid and reliable identification of degradation products supports maintenance decisions, quality control and design improvements.

Objectives and Study Overview

This study applies a dedicated FTIR-based Plastic Analyzer system to characterize deterioration on an automotive headlight cover. By comparing spectra from a discolored region and a transparent region, the aim was to identify base polymers and any coating or oxidation products responsible for yellowing.

Methodology and Instrumentation

The analysis combined the following components:

• IRSpirit Fourier Transform Infrared Spectrophotometer
• QATR-S single-reflection ATR accessory
• Plastic Analyzer Method Package with UV-damaged and thermal-damaged plastics libraries
• IR Pilot macro program for automated parameter setting

A yellowed area and an adjacent transparent area of the headlight cover were sectioned and analyzed by ATR-FTIR. Difference spectra were generated to isolate coating components.

Main Results and Discussion

Spectrum comparison revealed that both regions predominantly consist of polycarbonate (PC). Difference analysis of the transparent area against the yellowed area matched deteriorated polymethylmethacrylate (PMMA) from the UV-damaged library, suggesting a PMMA protective coating. Common broad OH stretching bands around 3400 cm−1 indicated oxidative degradation in both regions. In the yellowed zone, the absence of PMMA signals implied coating delamination following extended UV exposure, leading to pronounced polymer aging.

Benefits and Practical Applications of the Method

• Enables non-expert users to perform detailed polymer deterioration studies
• Identifies coating and base material contributions through library-assisted searches
• Supports quality control for automotive parts exposed to harsh environments
• Facilitates investigation of microplastics and environmental degradation

Future Trends and Potential Applications

Advances may include expanded spectral libraries covering novel polymers and additives, integration with machine learning for automated spectral interpretation, portable ATR-FTIR systems for in-field diagnostics, and applications in microplastic research and environmental monitoring.

Conclusion

The FTIR-based Plastic Analyzer approach successfully distinguished polycarbonate substrate and PMMA protective coatings, traced oxidative degradation, and explained the yellowing mechanism. This methodology offers robust, user-friendly tools for polymer degradation analysis in industrial and research settings.

Instrumention

• IRSpirit FTIR Spectrophotometer
• QATR-S Single-reflection ATR Accessory
• Plastic Analyzer Method Package (UV and thermal libraries)
• IR Pilot Macro Program

References

• Shimadzu Corporation. IRSpirit Fourier Transform Infrared Spectrophotometer Application News No. 01-00126-EN, First Edition, June 2021.