Question

The density and associated percent crystallinity for two polytetrafluoroethylene materials are as follows: rho(g/cm3) crystallinity (%) 2.104 51.1 2.280 76.9 (a) Compute the density of totally crystalline polytetrafluoroethylene. rhoc = g/cm3 (b) Compute the density of totally amorphous polytetrafluoroethylene. rhoa = g/cm3 (c) Determine the percent crystallinity of a specimen having a density of 2.27 g/cm3. % crystallinity =

Answer 1

To be able to calculate the density of totally amorphous and totally crystalline polytetrafluoroethylene, we will have to make use of the formula below:

% Crystalinity = ρₓ (ρ₃ - ρ₂) / ρₓ (ρ₃ - ρ₂) X 100......equation (1)

Where ρ₃ is the density of material of whic the percentage of crytalinity is to be determined. ρ₂ is the density of the totally amorphous polymer and ρₓ is the is the density of perfectly crystalline polymer.

Moving forward, we then move to substitute ρ₃ and the degree of crystallinity for the two points. it then gives us:

0.513 = ρₓ ( 2.144g/cm³ - ρ₂) / 2.144g/cm³ ( ρ₃ - ρ₂ )...........equation (2)

1.004ρₓ + 1.100ρ₂ = ρ₃ ρ₂

0.742 = ρₓ ( 2.144g/cm³ - ρ₂) / 2.215g/cm³ ( ρ₃ - ρ₂ ).............equation (3)

0.571 ρₓ + 1.644ρ₂ = ρ₃ ρ₂

Now, we go ahead to subtract equation (3) from equation (2)

0.473ρₓ - 0.544ρ₂ = 0

ρₓ = 1.150ρ₂

Moving forward, we hvae,

1.004 ( 1 .150ρ₂ ) + 1.009ρ₃ = ρₓ ( 1.150ρ₂)

Therefore,

ρₓ = 2.000g/cm³

However,

ρ₂ = 2.300g/cm³

(b)

% crystallinity = 87.9%

Step-by-step explanation: