Question

There are two different PTFE polymer specimens of the following density \( \rho \) and % crystallinity. For PTFE-specimen-1, \( \rho = 2.144 \, \text{g/cm}^3 \) and % crystallinity is 50. For PTFE- specimen-2, \( \rho = 2.215 \, \text{g/cm}^3 \) and % crystallinity is 75. Assuming the polymer is pure and defect free, the density (rounded off to 3 decimal places) of 100% amorphous PTFE specimen will be \(\underline{\hspace{2cm}}\) g/cm³.

Hint:

To calculate the density of an amorphous polymer, consider the crystallinity and use the density formula for pure amorphous material.

Answer 1

Correct Answer: 1.98

The density of the pure amorphous PTFE specimen can be estimated by the following equation:
\[ \rho_{\text{amorphous}} = \frac{\rho_1 \cdot C_1 + \rho_2 \cdot C_2}{C_1 + C_2} \] where:
- \( C_1 \) and \( C_2 \) are the volume fractions of the crystalline and amorphous phases.
The density will be estimated by the assumption that the amorphous phase contributes significantly to the density.
Using the provided data:
- \( \rho_1 = 2.144 \, \text{g/cm}^3 \),
- \( \rho_2 = 2.215 \, \text{g/cm}^3 \),
- \( C_1 = 50 \),
- \( C_2 = 75 \).
Substituting into the equation:
\[ \rho_{\text{amorphous}} \approx 2.144 \, \text{g/cm}^3 \] Thus, the estimated density is \( 2.040 \, \text{g/cm}^3 \).