Solid State Alkaline Depolymerization of Polyester Elastane Textiles in a Laboratory Kneader.

Area of Science:

• Polymer Science
• Materials Chemistry
• Sustainable Chemistry

Background:

• Elastane (EL) in polyester (PET) textiles complicates recycling due to thermal degradation and byproduct formation.
• Alkaline depolymerization is a promising method for PET recycling, but the impact of EL needs further investigation.

Purpose of the Study:

• To investigate the effect of elastane on alkaline depolymerization of PET.
• To assess the feasibility of monomer recovery from PET/EL blends under specific processing conditions.

Main Methods:

• Alkaline depolymerization of PET/EL blends (0-15 wt% EL) using solid NaOH under quasi-solid-state conditions (140°C, 5 min).
• Analysis of terephthalic acid (TA) yield and characterization of water-insoluble residues using differential scanning calorimetry (DSC) and 1H NMR.

Main Results:

• PET depolymerization was not significantly impaired by 5-15 wt% elastane, with terephthalic acid yields between 68-71%.
• Differential scanning calorimetry indicated modification of elastane during the depolymerization process.
• No detectable co-isolated aromatic diamines were found in the recovered terephthalic acid.

Conclusions:

• Robust monomer recovery from mixed PET/EL textiles is achievable via solvent-lean, solid-NaOH depolymerization.
• Residue analytics is crucial for quantifying elastane fate and achieving material balance in PET/EL recycling.