DRY SPINNING
In dry spinning the polymer is dissolved in a volatile solvent. Once dissolved, the polymer solution is extruded through the spinneret which is in an enclosed drying tower. The solution goes through a drying process in this tower, where the solvent is evaporated.
By courtesy of Encyclopaedia Britannica, Inc., copyright 1997; used with permission.
EQUIPMENT DESIGN
The spinning solution is often filtered many times to remove foreign materials that might cause thread defects or clogging in the machine. The solution is extruded into the drying tower through which hot air or other gases pass. The concentration of the polymer increases as the solvent evaporates, leaving a solid polymer filament behind. The solvent is later recovered from the gas by condensation or absorption and is then recycled.
Solvent selection is very important, and is based on boiling point, latent heat of vaporization, thermal stability, toxicity, and inertness. Non-polar solvents are often preferred because of their low boiling points and heats of vaporization. However, non-polar solvents are prone to build-ups of electrostatic charge, which can be very dangerous.
ADVANTAGES
DISADVANTAGES
Better than melt spinning for temperature-sensitive polymers.
Faster production rates than melt and wet spinning.