Contaminant Category
Chemical impurities that are not deliberately introduced during polymer synthesis are categorized as unintended residues. These compounds, termed non intentionally added substances, include catalyst residues and contaminants from the recycling stream. Their identification in recycled polyester is critical because they can affect the color and safety of the final textile product.
Origin Classification
Recycled post-consumer polyethylene terephthalate often contains trace amounts of materials from previous use or sorting errors. Some of these substances originate from the breakdown of additives during the melting process, while others come from printing inks or adhesive residues. Identifying these sources helps recyclers select the appropriate washing and filtration methods.
Analytical Verification
Gas chromatography coupled with mass spectrometry is used to detect these volatile and semi-volatile chemicals in resin batches. The test protocol measures the concentration of each compound to ensure it falls below established safety thresholds. This rigorous laboratory inspection is required before recycled polymer can be certified for high-exposure textile applications.
Risk Management
Advanced filtration and intensive vacuum degassing are employed to remove these trace contaminants during melt spinning. Because non intentionally added substances can migrate to the surface of the fiber, their reduction is essential for fabrics that come into direct contact with the skin. Continuous testing during yarn production ensures that the final garment meets international safety standards.
Recyclers often combine super-washing steps with solid state polymerization to pull these volatile chemicals out of the polymer matrix before the yarn is spun. This multi-stage purification protocol secures the safety of recycled apparel.
