Linking Degradation Pathways, Additive Transformation, and Contaminant Profiles in Post-Consumer HDPE: Implications...

Area of Science:

• Polymer Chemistry
• Materials Science
• Analytical Chemistry

Background:

• Chemical complexity in post-consumer plastics hinders high-quality recycling.
• Understanding the origins and transformations of chemical compounds in recycled plastics is crucial.

Purpose of the Study:

• To analyze the chemical composition of post-consumer high-density polyethylene (HDPE).
• To investigate relationships between compound origin, degradation pathways, and contaminant profiles in recycled HDPE.
• To identify factors influencing the chemical makeup of recycled HDPE.

Main Methods:

• Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) was used to analyze HDPE samples.
• Over one hundred organic compounds were detected and classified.
• Multivariate analysis was employed to explore relationships between chemical profiles and sample origins.

Main Results:

• Polymer degradation products were the most diverse group, indicating significant matrix transformation.
• Additive-derived compounds and persistent contaminants like fluoropolymers were frequently detected.
• Chemical composition was not correlated with product category but influenced by degradation, additive transformation, and contamination.

Conclusions:

• The chemical profile of recycled HDPE is shaped by multiple independent factors.
• Advanced polymer degradation and contamination are significant challenges in recycling.
• Chemistry-informed recycling strategies are necessary to address the complexity of recycled plastics.