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Physical & Chemical properties

Vapour pressure

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The vapour pressure of tetrafluoroethylene was determined at thermodynamic equilibrium between gas and liquid phases for temperatures between -32 and +31.4°C. Between +2 and 24.3°C the vapour pressure of TFE ranged between 17300 and 32395 hPa.Close agreement between the results obtained in this work by ICI and earlier work by DuPont was demonstrated.

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Additional information

Table A. TFE Vapour Pressure vs Temperature - Experimental Measurements

 Temp

 °C

VP

 hPa 

-32.0

5859

-28.0

6755

-21.5

8616

-12.0

11855

 +2.0

17300

+14.5

25020

+24.3

32395

+29.7

35979

+31.2

37220

 +31.4

37358

The experimental data can be represented by the two equations:

at -32 to 0°C       

log10P = 4.9258 - 580.2 / T + 230

at 0 to 33°C       

 log10P = 5.2717 - 659.6 / T + 230       

where P = pressure (psia) and

T = temperature (°C)

Results calculated from these equations were compared with those obtained in earlier work by DuPont

Table B: Vapour Pressure (VP) of TFE vs Temperature (T°C) Comparison of Smoothed Results from this work (ICI) with DuPont Values

T °C

VP hPa

(ICI)

VP hPa

(DuPont)

-76.6

-

1013

-75.5

1013

-

-60

2275

2206

-50

3446

3446

-40

5101

5032

-30

7306

7237

-20

10063

9994

-10

13372

13509

0

17438

17920

10

23021

23297

20

29638

29569

30

37429

36944

33*

39977

39564

*critical temperature and pressure

Thus from the comparison of results in Table B good agreement is confirmed between this work by ICI and that conducted earlier by DuPont.

Using the ICI equation at vapour pressure of 33.5 bar can be calculated for TFE at 25°C. This value compares well with that of 33.1 bar obtained at the same temperature by Renfrew and Lewis (1946) using the equation logVP (psi) = 5.5906 - 866.84/T, where T is in Kelvin.

Reference

Renfrew MM, Lewis EE, 1946. Polytetrafluoroethylene: Heat-resistant, chemically inert plastic. Industrial and Engineering Chemistry 38(9), 870 - 877.