Influence of Spin Finish on Degradation, Functionalization and Long-term Storage of Polyethylene Terephthalate Fabrics Dedicated to Ligament Prostheses

Spin finish oil applied to poly(ethylene terephthalate) (PET) fibers is shown to alter the surface properties of commercial PET fibers in storage over extended storage times. Oil removal by solvent extraction as required for their applications is shown to be changed; fiber surface chemistry, particularly surface functionalization with anionic polymer grafts, is altered, and surface mechanical properties are altered. Spin finish oxidation in storage is proposed to produce these fiber changes in storage important to their biomedical performance. Background: Poly(ethylene terephthalate) (PET) fabrics surface-functionalized using anionic polymer grafts to enhance their biocompatibility, cell adhesion, proliferation and functional performance as PET ligament prostheses have been developed for medical application in vascular and ligament prostheses. Here, we provide new evidence for deleterious effects of uncontrolled storage times and conditions on the final properties of PET medical fabrics and devices, specifically alteration and degradation of applied spin finish oil and fabric fiber surface properties, and limits to surface functionalization of PET fibers important to for medical uses.Results: Textile spin finish oil effects from 2- to 25-year storage times on PET fiber degradation and surface functionalization with anionic polymers were analyzed using FTIR, DSC and by quantitative AFM nano-mechanical profiling. Degradation of the spin-finish oil/fiber interface reduced oil Soxhlet extraction efficiency due to oil solubility changes in diethyl ether or n-hexane extraction solvents. However, solvent tetrahydrofuran was shown to be the most efficient extraction solvent even after long fabric storage times, facilitating further efficient surface functionalization of PET fabrics. Surface mechanical properties of PET fibers and fabrics over storage times spanning 2 to 25 years were investigated by using AFM-Peakforce QNM. Results showed significant and dramatic reduction of the surface elastic modulus of degraded PET fiber surfaces, with surface stiffness decreasing from 2.3 GPa for optimal (2-year) conditions of storage (PET 2018) to 50-85 MPa for extended storage (to 25 year) periods (PET2009 and PET1993). Conclusion: The ambient aging of textile spin finish oil with PET surfaces was shown to induce PET surface degradation, limiting oil removal, limiting further PET fiber surface graft functionalization, and compromising mechanical properties. Moreover, residual degraded finishing oils likely contained oxidation products from extended storage that alter PET fabrics.