[Metals in recycled polyethylene terephthalate and discrimination method for its use]

Area of Science:

• Analytical Chemistry
• Materials Science
• Polymer Recycling

Context:

• Recycled polyethylene terephthalate (PET) is increasingly used in various applications.
• Understanding the elemental composition of recycled PET is crucial for safety and quality assessment.
• Distinguishing between different recycling methods (physical, superclean, chemical) is important for material traceability.

Purpose:

• To analyze the metallic elements present in recycled PET using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
• To investigate the correlation between specific metals (Ge, Sb, Co, P, Si) and different PET recycling processes.
• To determine the safety of metals found in recycled PET and establish a method for identifying recycling types.

Summary:

• ICP-MS analysis after microwave digestion revealed that physically and superclean-recycled PET contained germanium (Ge) and antimony (Sb), with occasional traces of cobalt (Co), phosphorus (P), or silicon (Si).
• Chemically recycled PET contained only Ge or Sb, and sometimes Co. Lead (Pb) and cadmium (Cd) were not detected in any recycled PET samples.
• The presence of both Ge and Sb serves as a reliable indicator for identifying products manufactured using physically or superclean-recycled PET, with approximately half of sheet molding products utilizing this method.

Impact:

• Confirms the absence of safety concerns regarding metal content in recycled PET.
• Provides a robust method for differentiating between physical/superclean and chemical recycling processes based on elemental signatures.
• Enables accurate identification of recycled PET types in consumer products, supporting circular economy initiatives.