How do you make spandex?

Spandex is a synthetic fiber. It is typically made through one of four processes including melt extrusion, reaction spinning, solution dry spinning, and solution wet spinning. Most of the spandex produced is done so using the solution dry spinning method. In the dry spinning method, a macro glycol with a diisocyanate monomer to produce a prepolymer. The prepolymer is then reacted with an equal amount of diamine. The resulting solution is then cured into fibers and forced through a spinneret. Once the solution is passed through the spinneret, it forms strands of liquid polymer which is heated in the presence of nitrogen and a liquid solvent. This forms strands of solid fiber which are bundled together to a desired thickness. The strands are then treated with a finishing agent. For clothing, spandex is often mixed with either cotton or polyester.