Circularity in Polyamide Textiles: Enhancing Recycled Polymer Molar Mass with Carbodiimide Linear Coupling

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Engineering

Background:

• Textile waste, particularly polyamide 6 (PA6), presents significant environmental and economic challenges.
• Hydrolytic degradation during recycling lowers PA6 molar mass, limiting its circularity.

Purpose of the Study:

• To investigate the use of carbodiimide (CDI) as an antihydrolysis agent and chain extender for PA6 fabric recycling.
• To understand the mechanisms of molar mass recovery and the effect of humidity on PA6 recycling.

Main Methods:

• Recycling of PA6 fabrics with a CDI additive under varying humidity conditions.
• Rheological analysis to measure molar mass changes.
• ¹³C NMR and Time Domain NMR for molecular investigation.
• Density Functional Theory (DFT) calculations.

Main Results:

• CDI significantly reduced PA6 degradation in both dry and humid conditions.
• Molar mass increased by 40% (dry) and 75% (wet) with CDI.
• NMR and DFT analyses indicated CDI promotes linear chain extension, not branching.

Conclusions:

• CDI effectively enhances the recycling of PA6 fabrics by mitigating hydrolysis and increasing molar mass.
• This method supports cradle-to-cradle recycling, improving textile circularity and reducing environmental impact.