Question

The objective of the filament drawing process is to improve the \(\underline{\hspace{2cm}}\) of a fibre.

• A. Crystallinity
• B. Molecular orientation
• C. Density
• D. Thickness

Hint:

Think of drawing like combing tangled hair. - Before Drawing: Polymer chains are tangled and random. - After Drawing: Polymer chains are combed straight and aligned (molecular orientation). This alignment makes the fiber much stronger.

Answer 1

The Correct Option is B

Step 1: Define the "drawing" process. Drawing is a post-spinning process where newly formed synthetic filaments are stretched to several times their original length. 
 

Step 2: Understand what happens at a molecular level during drawing. In the as-spun state, the long polymer chains in the fiber are randomly coiled and arranged. The drawing process pulls these chains, causing them to uncoil and align themselves parallel to the fiber axis. This alignment is called "molecular orientation." 
 

Step 3: Analyze the consequences of molecular orientation. When the molecules are oriented, they can pack more closely together and exert stronger intermolecular forces on each other. This leads to a significant increase in the fiber's strength (tenacity) and stiffness (modulus), which are the primary goals of drawing. While crystallinity (A) may also increase as a result of the better packing (a phenomenon called stress-induced crystallization), the fundamental objective and direct change is the improvement in molecular orientation. Density (C) will increase slightly and thickness (D) will decrease, but these are consequences, not the primary objective. 

Conclusion: The main objective of drawing is to align the polymer chains along the fiber axis, i.e., to improve molecular orientation, which in turn increases strength.