Fibre Surface Chemistry and Zeta Potential
topic
PET surface is hydrophobic (contact angle 70–80°), with low surface energy (43 mN/m). Surface contains carboxyl and hydroxyl end groups detectable by XPS (C 1s peak deconvolution: aromatic C at 284.5 eV, C–O at 286.5 eV, C=O at 288.5 eV, ester at 289.5 eV). Zeta potential in aqueous solution at pH 6: −15 to −25 mV (from carboxyl groups). Surface energy determines adhesion in composites, finishing uptake, and soiling behaviour.
Role
Fibre surface chemistry governs adhesion to coatings and matrices, wetting behaviour, antistatic behaviour, and finishing chemical uptake. XPS and contact angle analysis are essential characterisation tools for surface-engineered polyester.