Question

The viscose solution should have a viscosity

• A. 30--50 C-poise
• B. 30--50 poise
• C. 150--200 poise
• D. 15--20 C-poise

Hint:

Proper dope viscosity ensures smooth extrusion and uniform fibre formation in wet spinning.

Answer 1

The Correct Option is C

Step 1: Understanding viscose spinning requirements.
Viscose solution must have sufficient viscosity to form a continuous filament during extrusion through the spinneret without breaking.
Step 2: Importance of higher viscosity.
Low-viscosity solutions lead to filament breakage, while excessively high viscosity causes processing difficulties. An optimum range is required.
Step 3: Standard industrial practice.
In viscose rayon manufacturing, the viscose dope viscosity is typically maintained between 150 and 200 poise for stable spinning.
Step 4: Conclusion.
Therefore, the correct viscosity range is 150--200 poise.

Answer 2

Viscose dope viscosity must be high enough to hold a continuous filament together as it is extruded through the spinneret, without being so thick that it cannot be pumped and filtered smoothly. Checking each stated range against this processing requirement helps identify the right one.

1. 30-50 C-poise: This range is far below the level needed to hold a continuously extruded filament together during coagulation; a dope this thin would break up before the filament could set.
2. 30-50 poise: Even in standard poise units, this range is too low for stable viscose spinning; such a thin dope tends to produce broken, uneven filaments rather than a continuous strand.
3. 150-200 poise: This is the range that gives the dope enough body to be drawn into a continuous filament through the spinneret while the coagulation bath sets the cellulose, without being too viscous to pump, filter, and de-aerate reliably.
4. 15-20 C-poise: This is even lower than the other low-viscosity options and shares the same problem of being unable to sustain a continuous filament during spinning.

Only a dope viscosity in the higher, three-digit poise range provides the balance of flowability and filament-forming strength that viscose spinning needs.

Therefore, the correct answer is 150-200 poise.