Cross-Section Geometry and Light Scattering
topic
Circular cross-section PET has characteristic bright lustre from specular reflection. Trilobal cross-section (three-lobed spinnerets) produces silk-like lustre and softer handle. Hollow fibre (annular spinnerets, 10–30% void) has lower density, improved thermal insulation, and cotton-like moisture behaviour. Flat ribbon fibres (slot spinnerets) produce high-cover fabrics. Cross-section quantified by form factor and aspect ratio from optical microscopy.
Role
Cross-section engineering is the primary tool for modifying the optical and tactile properties of polyester without changing polymer chemistry — enabling simulation of natural fibre aesthetics and design of functional performance fibres.