Deterioration Analysis of Automobile Headlight Cover by Plastic Analyzer

Importance of the Topic

Automobile headlight covers made from plastic alloys are prone to UV- and heat-induced degradation during outdoor use, leading to discoloration and loss of mechanical performance. Reliable identification of degradation products facilitates maintenance decisions and design improvements.

Study Objectives and Overview

The aim is to demonstrate the application of the IRSpirit Fourier Transform Infrared Spectrophotometer coupled with Shimadzu Plastic Analyzer Method Package for deterioration analysis of a PC-based automotive headlight cover. A comparative investigation between transparent and yellowed areas clarifies degradation pathways and material composition.

Methodology and Instrumentation

The analysis employed the Plastic Analyzer system comprising:

• IRSpirit Fourier Transform Infrared Spectrophotometer
• QATR-S single-reflection ATR measurement accessory
• Plastic Analyzer Method Package with UV-damaged and thermal-damaged plastics libraries

Sample preparation involved isolating transparent and yellowed sections of the headlight cover, followed by ATR spectral acquisition using preset parameters in the IR Pilot macro.

Main Results and Discussion

Overlay of ATR spectra from both regions indicated polycarbonate (PC) as the main polymer in all areas. The yellowed section spectrum matched thermally aged PC, while the transparent section spectrum contained an additional component identified as polymethyl methacrylate (PMMA) from the UV-damaged plastics library. Key findings:

• PC was confirmed as the base material for headlight cover in both regions.
• O–H stretching absorptions around 3400 cm–1 indicated oxidative degradation in both parts.
• PMMA coating was detected on the transparent area, suggesting a UV protective layer.
• Absence of PMMA in the yellowed region implied coating loss after extended UV exposure.

Benefits and Practical Applications

The Plastic Analyzer approach offers:

• Rapid and user-friendly degradation and contaminant analysis for plastics.
• Comprehensive identification using UV and thermal damage libraries.
• Non-requiring flat specimens, enabling ATR analysis of irregular surfaces.
• Potential for microplastics research and environmental monitoring.

Future Trends and Opportunities

Expanding degraded polymer spectral libraries to cover a broader range of materials and aging conditions will enhance diagnostic accuracy. Integration with automated data analysis and machine learning could streamline interpretation, supporting applications in automotive quality control, recycling, and environmental impact assessment.

Conclusion

The study illustrates the effectiveness of combining FTIR-ATR measurement with specialized aging libraries to pinpoint material composition and deterioration mechanisms in automotive plastics, enabling informed maintenance and design strategies.