GATE Textile Engineering and Fibre Science Practice Quiz

Question 1

In a semicrystalline fibre, which structural feature primarily causes the broad diffuse halo observed in wide-angle X-ray diffraction, in addition to sharp crystalline reflections?

Accepted Answer

Randomly packed amorphous chain segments

Question 2

For a fibre-forming polymer, which change generally increases the degree of crystallinity most directly during solidification from the melt?

Accepted Answer

Moderate to slow cooling allowing chain rearrangement

Question 3

A fibre sample shows a measured density of 1.360 g/cm3. If the densities of fully amorphous and fully crystalline phases are 1.330 g/cm3 and 1.400 g/cm3 respectively, what is the approximate mass fraction crystallinity by the density method?

Accepted Answer

0.43

Question 4

During fibre drawing, why can excessive draw rate suppress the expected increase in crystallinity even though orientation rises?

Accepted Answer

Chains may align but lack sufficient time for ordered packing into crystals

Question 5

A drawn fibre shows higher tensile modulus after processing. Which structural change is the most likely direct reason if chemical composition is unchanged?

Accepted Answer

Increase in molecular orientation and crystallinity

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