Surface Analysis of PET Film Using a Benchtop MALDI-TOF Mass Spectrometer

Significance of the Topic

The analysis of polymer film surfaces is critical for quality control and durability assessment in industrial applications. Understanding oligomer migration and surface deposits on films such as polyethylene terephthalate (PET) can prevent defective batches and processing problems. A compact and cost effective analytical tool that can detect surface compounds with high sensitivity supports routine monitoring in manufacturing and research settings.

Objectives and Study Overview

This study aimed to demonstrate the capability of a benchtop MALDI 8020 time of flight mass spectrometer for simple surface profiling of PET film. The experiment compared untreated film with film thermally treated at 100 °C to identify differences in oligomer distribution and antioxidant residues on the surface.

Methodology and Instrumentation

Sample Preparation

• A commercial PET film sheet was divided into two: one piece heated at 100 °C for several hours, the other kept at room temperature.
• Both samples were fixed to a stainless steel MALDI plate using conductive tape and coated with a matrix solution of 20 mg/mL dithranol and 3 mg/mL sodium trifluoroacetate in THF.

Measurement Conditions

• Instrument: benchtop MALDI 8020 linear mode positive ion TOF mass spectrometer
• Laser: 200 Hz solid state
• Flight tube length: 0.85 m, enabling isotope separation near m/z 4000
• Load lock chamber for rapid target exchange while maintaining vacuum

Main Results and Discussion

Optical microscopy revealed slight whitening of the film after thermal treatment. Mass spectra showed molecular ions of the antioxidant irganox1010 (Na adduct) at m/z 1199 in both samples. The cyclic PET trimer (Na adduct) at m/z 599 appeared only on the thermally treated film. Spatial mapping of these ions illustrated that the trimer distribution increased significantly after heating, while irganox1010 remained evenly distributed regardless of treatment.

Benefits and Practical Applications

The benchtop MALDI 8020 enables rapid, high sensitivity surface profiling without the expense and footprint of larger instruments. It facilitates:

• Routine quality assurance of polymer films
• Failure analysis by detecting surface contaminants and oligomer migration
• Material degradation and durability testing through direct surface measurements

Future Trends and Potential Applications

Continued miniaturization and cost reduction in MALDI TOF systems will expand their adoption in polymer and materials science. Potential developments include:

• Integration with imaging for detailed surface mapping
• Automated sample handling for high throughput screening
• Combination with other analytical techniques to correlate chemical and structural information
• Applications in real time monitoring of production lines

Conclusion

A compact benchtop MALDI TOF instrument can effectively distinguish surface oligomers on PET film before and after thermal treatment. Performance in linear mode matches that of conventional systems, while offering advantages in size, cost, and ease of use. This approach promises to support routine analysis and material evaluation in industrial laboratories.

References

Application note B72 Shimadzu MALDI TOF Mass Spectrometry Surface Analysis of PET Film Using a Benchtop MALDI TOF Mass Spectrometer First Edition Nov 2017