Question:
In the first heating cycle of a differential scanning calorimetry (DSC) experiment, an as-spun Nylon 6 fibre showed an enthalpy change of 40 J/g during cold crystallization and an enthalpy change of 150 J/g during melting. If the heat of fusion of 100% crystalline Nylon 6 is 240 J/g, the percentage degree of crystallinity of as-spun Nylon 6 fibre (rounded off to 1 decimal place) is _________
In the first heating cycle of a differential scanning calorimetry (DSC) experiment, an as-spun Nylon 6 fibre showed an enthalpy change of 40 J/g during cold crystallization and an enthalpy change of 150 J/g during melting. If the heat of fusion of 100% crystalline Nylon 6 is 240 J/g, the percentage degree of crystallinity of as-spun Nylon 6 fibre (rounded off to 1 decimal place) is _________
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To calculate the degree of crystallinity, add the enthalpy change during cold crystallization and melting, then divide by the heat of fusion of 100% crystalline polymer, and multiply by 100.
Updated On: Apr 28, 2025
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Solution and Explanation
Given:
Enthalpy change during cold crystallization, ΔHₐ = 40 joules/gram
Enthalpy change during melting, ΔHₘ = 150 joules/gram
Heat of fusion for 100% crystalline Nylon 6, ΔHₓ = 240 joules/gram
Step 1: Calculate Net Enthalpy of Melting (ΔHₙₑₜ)
The net enthalpy of melting accounts for the heat absorbed during melting minus the heat released during cold crystallization:
ΔHₙₑₜ = ΔHₘ - ΔHₐ
ΔHₙₑₜ = 150 joules/gram - 40 joules/gram = 110 joules/gram
Step 2: Calculate Degree of Crystallinity (X)
The degree of crystallinity is the ratio of the net enthalpy of melting to the heat of fusion of 100% crystalline Nylon 6:
X = (ΔHₙₑₜ / ΔHₓ) × 100%
X = (110 joules/gram / 240 joules/gram) × 100% = 45.8%
Enthalpy change during cold crystallization, ΔHₐ = 40 joules/gram
Enthalpy change during melting, ΔHₘ = 150 joules/gram
Heat of fusion for 100% crystalline Nylon 6, ΔHₓ = 240 joules/gram
Step 1: Calculate Net Enthalpy of Melting (ΔHₙₑₜ)
The net enthalpy of melting accounts for the heat absorbed during melting minus the heat released during cold crystallization:
ΔHₙₑₜ = ΔHₘ - ΔHₐ
ΔHₙₑₜ = 150 joules/gram - 40 joules/gram = 110 joules/gram
Step 2: Calculate Degree of Crystallinity (X)
The degree of crystallinity is the ratio of the net enthalpy of melting to the heat of fusion of 100% crystalline Nylon 6:
X = (ΔHₙₑₜ / ΔHₓ) × 100%
X = (110 joules/gram / 240 joules/gram) × 100% = 45.8%
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