Question

The density and associated percent crystallinity for two polytetrafluoroethylene materials are as follows:

ρ(g/cm3)		crystallinity (%)
2.031		55.5
2.240		75.4

(a) Compute the densities of totally crystalline polytetrafluoroethylene.
(b) Compute the densities of totally amorphous polytetrafluoroethylene.
(c) Determine the percent crystallinity of a specimen having a density of 2.06 g/cm3.

Answer 1

Solution :-

Part A) solving for the density of the crystalline

Pc = ps1 ps2 (C2-C1)/[Ps2(C2-1)-ps1(C1-1)]

Ps1 =2.031 g/cm3   and c1 = 0.555

Ps2 =2.240 g/cm3 and c2 = 0.754

Lets put the values in the formula

Pc = (2.031 * 2.240)(0.754-0.555) / [(2.240*(0.754-1))-(2.031*(0.555-1))

Pc = 2.566 g/cm3

So the densities of the totally crystalline form is 2.566 g/cm3

Part b lets calculate the density of the amorphous form

Pa = ps1ps2 (C1-C2)/ c1ps1 – c2ps2

Pa = (2.031 * 2.240)(0.555-0.754) / ((2.031*0.555)-(2.240*0.754))

Pa = 1.612 g /cm3

So the density of the amosrphous form = 1.612 g /cm3

Part c

Detmining the percent crystanality if the density is 2.06 g /cm3

% C = [pc(Ps –pa)/ Ps(Pc-pa)]*100%

       = [(2.566(2.06-1.612) / (2.06(2.566-1.612)]

       = 58.49 %

So the percent crystanility = 58.49 %