Monitoring of Wool Stretching Process Using Polarized Second Harmonic Generation

The study demonstrates the use of polarized second harmonic generation (P-SHG) imaging to monitor structural changes in wool fibers during industrial stretching. P-SHG effectively detects changes in α-keratin alignment and cortical interface reconstruction, with the effective pitch angle decreasing from 54° ± 1° to 33° ± 3° after stretching. This indicates a reorganization of keratin molecules, transitioning from α-helix to β-sheet structures. The study also highlights the role of oxidation in breaking disulfide bonds, facilitating molecular reorganization. These findings, validated by techniques like SEM, POM, XRD, and RS, suggest that P-SHG is a promising method for real-time monitoring of wool fiber structural changes, offering advantages such as non-invasive detection and high-resolution analysis for the wool industry.