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Teflon
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What is Teflon?
What is "virgin Teflon"?
What are some radiological characteristics of Teflon?


What is Teflon?

Teflon (R) is Polytetrafluoroethylene (or Polyethylene Tetrafluoride).
Monomer Formula: C2F4
Monomer Molecular weight: 100.02
Density = 2.20 g/cm3
IUPAC International Chemical Identifer: InChI=1/C2F4/c3-1(4)2(5)6
CAS Registry Number: 9002-84-0

Polytetrafluoroethylene's chemical structure is:

             F            F
             |            |
             |            |
?------------C------------C-----------?
             |            |
             |            |
             F            F
Sources:
http://www.chemindustry.com/chemicals/6246585.html
http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=227


What is "virgin Teflon"?

Virgin Teflon is "pure" Teflon, that is, it has no fillers (impurities) added. The solid, Teflon spine supplied with Data Spectrum's Elliptical Lung Spine Body Phantom (ECT/LUNG/P) is made of virgin Teflon. (Note that some special order requests in the past were supplied with a "mechanical" Teflon spine phantom.)


What are some radiological characteristics of Teflon?

To start with, please read reference "X-Ray Attenuation and Absorption for Materials of Dosimetric Interest" by J. H. Hubbell and S. M. Seltzer.
According to Hubbell and Selzer Teflon (R) has the following properties:
  • Material: Polytetrafluoroethylene, (Teflon)
  • Z/A: 0.47993
  • I (eV): 99.1
  • Density = 2.20 g/cm3
  • Composition (Z : Fraction by weight):
    • 6: 0.240183
    • 9: 0.759818
How these data are used to compute the mass attenuation coefficients (in units of cm2/g) is explained at: http://physics.nist.gov/PhysRefData/XrayMassCoef/chap2.html

One needs the total (that is, the sum of the cross sections for the photoelectric absorption, Compton scattering, etc.) cross section as a function of energy.

FYI: The NIST has an interactive web program called XCOM that will compute the mass attenuation coefficient for elements, chemical compounds or mixtures. You enter the chemical formula (such as "C2F4" for Teflon (R)), specify an energy range and let it perform the calculations.

The linear attenuation coefficient (what we are most interested in) is simply the mass attenuation coefficient multiplied by the density.

For example, at 140 keV, the mass attenuation coefficient (from the output of the program XCOM) is 0.134 cm2/g. Thus the linear attenuation coefficient is 0.295 per cm.

At ~511 keV, the mass attenuation coefficient (from the output of the program XCOM) is 0.0829 cm2/g. Thus the linear attenuation coefficient is 0.182 per cm.

For details of a sample calculation by XCOM for Teflon from 10-1000 keV, please see this link.

 

©2007 Data Spectrum Corporation . . . . . Last Rev: 17 Mar. 2007