Chromatogram-Kendrick Mass (CKM) Plot for Comprehensive Visualization of Pyrolysis Products in Polyolefin Blends

Area of Science:

• Analytical Chemistry
• Materials Science
• Polymer Chemistry

Background:

• Analyzing complex polymer mixtures, especially recycled materials, presents significant challenges.
• Pyrolysis gas chromatography/time-of-flight mass spectrometry (Py-GC/TOFMS) generates high-dimensional data.
• Existing visualization methods struggle to comprehensively interpret these complex datasets.

Purpose of the Study:

• To introduce a novel visualization technique, the chromatogram-Kendrick mass (CKM) plot.
• To demonstrate the CKM plot's utility in analyzing pyrolysis products from polymer blends.
• To evaluate the thermo-oxidative degradation of polypropylene (PP)/polyethylene (PE) blends.

Main Methods:

• Development of the chromatogram-Kendrick mass (CKM) plot integrating retention time, intensity, m/z, and Kendrick mass defect (KMD).
• Application of the CKM plot to PP/PE blends subjected to varying thermo-oxidative degradation.
• Utilizing field ionization Py-GC/TOFMS for data acquisition.

Main Results:

• The CKM plot effectively visualizes four-dimensional Py-GC/TOFMS data, enabling intuitive interpretation.
• Untreated PP/PE yields hydrocarbon ions; degraded samples show abundant oxygen-containing ions.
• CKM plots clearly differentiate PP- and PE-derived ions based on retention time and identify oxidative isomers.

Conclusions:

• The CKM plot is a powerful tool for distinguishing pyrolysis products from PP and PE in blends.
• It facilitates the elucidation of degradation trends and the evaluation of recycled polymer materials.
• PP undergoes preferential oxidation over PE in blends due to tertiary hydrogen lability.