Question

In wet spinning process, the solvent removal and fiber solidification takes place during \(\underline{\hspace{2cm}}\) stage.

• A. Drawing
• B. Wet coagulation
• C. Span finish
• D. Heat setting

Hint:

Remember the solidification methods for different spinning processes: - Melt Spinning: Solidifies by Cooling. - Dry Spinning: Solidifies by Evaporating the solvent in hot air. - Wet Spinning: Solidifies by Coagulating in a liquid bath.

Answer 1

The Correct Option is B

Step 1: Understand the wet spinning process. This process is used for polymers that need to be dissolved in a solvent to be spun (e.g., acrylic, viscose rayon). The polymer solution is extruded through a spinneret. 
 

Step 2: Analyze the stages. After extrusion, the filaments of polymer solution must be solidified. In wet spinning, this is done by extruding them directly into a liquid "coagulation bath." 
 

Step 3: Define the "Wet coagulation" stage. The coagulation bath is a liquid in which the polymer is insoluble, but the solvent is soluble. When the extruded filaments enter the bath, the solvent diffuses out of the filaments and into the bath, while a non-solvent from the bath may diffuse into the filaments. This removal of the solvent causes the polymer to precipitate and solidify, forming the fiber. This stage is called wet coagulation.

Step 4: Evaluate the other options. 
- Drawing: This is a later stage where the solidified fibers are stretched to align the polymer chains and improve strength. 
- Span finish: This refers to applying a finish to the fiber, not solidifying it. 
- Heat setting: This is a process used for thermoplastic fibers to impart dimensional stability, usually done after drawing. 

Conclusion: The removal of solvent and solidification of the fiber in wet spinning occurs during the wet coagulation stage.