Dry spinning of synthetic polymer fibers

Dry spinning is the fiber formation process that transforms a high vapor pressure polymer solution to a solid fiber by controlled fiber evaporation in the spinline. The key variables in dry spinning are heat transfer, mass transfer and stress on the filament. The spinning fiber reaches its final velocity/final denier when the stress applied to the spinning filament is no longer sufficient to draw the fiber to a smaller diameter. Solvent evaporation proceeds from the fiber surface inwards, often leading to a skin-core structure with trapped solvent in the fiber interior. Diffusion of this residual solvent can lead to the collapse of cylindrical fiber to the characteristic 'dogbone' shape often associated with dry spun fibers. This shape is also responsible for improved comfort and fabric cover. Most important of the dry spun fibers and cellulose acetate (CA), cellulose triacetate(CTA) and acrylics. Other fibers that are wet spun include spandex, polybenzimidazole (PBI) and polyvinylchloride (PVC).