Dry spinning, wet spinning and gel spinning.

Dry spinning.

• In dry spinning the polymer is dissolved in its solvent and then extruded, as the fibre emerge from the spinneret the solvent is evaporated off by hot air.
• The solvent in most cases is collected and reused.
• The polymer used in this method are acetate, triacetate, acrylics, modacrylics, spandex, Vinyon and PBI.
• The process is illustrated in fig below.

  

  Mechanism of dry spinning.

Wet spinning.

• This is the oldest method.
• This type of spinning is required by a polymer which require dissolving in a solvent to be spun.
• This method is named wet spinning because the polymer is extruded directly into the liquid bath.
• Since the polymer is extruded directly into the liquid, the filament experience a greater drag force than that of polymer extruded in air, due to which speed of this process is reduced as compare to the melt and dry spinning.
• This process is based on precipitation.
• The polymer fibre spun using this method include acrylics, spandex, aramid and rayon.
• This process is illustrated from figure below.

  

  Mechanism of wet spinning.

Gel spinning.

• This is a special process used for obtaining high tensile strength and special property polymers.
• This process is also known as dry- wet spinning,as the filament is first pass through air and then cooled in a liquid bath.
• The gel spinning method is used for obtaining some high tensile strength polyethylene and aramid fibres.
• This process is illustrated from figure below.

  

  Mechanism of gel spinning.