If a sample has very low crystallinity, relative to a higher crystallinity sample, its modulus is expected to be:

• A. Higher
• B. The same
• C. Unpredictable
• D. Lower, due to less crystalline stiffening

Answer: (D)

Stiffness increases with how much of the material is crystalline. Crystalline regions are highly ordered and resist deformation, so they act as rigid, load-bearing parts within the polymer. When crystallinity is higher, more of the material behaves like these stiff regions, boosting the overall modulus. If a sample has very low crystallinity, there are fewer of these stiff regions to carry the load, making it easier to deform under the same stress. That’s why its modulus is lower than that of a more crystalline sample. The other options don’t fit because, in semicrystalline polymers, increasing crystallinity generally raises the modulus, not keeps it the same or makes it unpredictable.