Optical Adjustment
Changing the way light bends as it passes through a synthetic fiber alters the visual appearance and luster of the finished textile. Methods of refractive index modification include the addition of delustrants like titanium dioxide to the polymer melt before extrusion. This process scatters the light internally, turning a shiny fiber into a matte or semi dull one.
Chemical Treatment
Surface coatings or chemical baths can also be used on finished yarns to change their light handling properties. In the case of refractive index modification, the goal might be to increase the brilliance of a silk substitute or to create a specialized optical effect. The change affects how the eye perceives the depth of the color.
Luster Control
Designers use these techniques to create fabrics that range from high gloss satins to chalky, opaque crepes. Achieving a successful refractive index modification requires precise control over the particle size of the additives. If the particles are too large, they can weaken the fiber and cause breakages during spinning.
The process also influences the uv protection properties of the fabric by blocking or scattering harmful rays.
Aesthetic Result
Final garments benefit from a more luxurious hand and a more sophisticated interaction with ambient light. The modification is permanent and cannot be washed out of the fiber.
