Table
2
Typical Properties* of Tefzel Fluoropolymer Resin
|
--
|
ASTM
Standard
|
Units
|
Tefzel
Fluoropolymer
|
| Mechanical
Properties: |
| Specific
Gravity |
--
|
D792
|
1.70
|
| Tensile
Strength |
D638
|
psi
|
6,500
|
| Elongation |
D638
|
%
|
300
|
| Flexural
Modulus |
D790
|
psi
|
170,000
|
| Folding
Endurance |
D2176
|
(MIT)
cycles
|
6-12
x 10
|
| Impact
Strength |
D256
|
Ft-lb/in.
|
No
Break
|
| Hardness |
D2240
|
Shore
D
|
67
|
| Coefficient
of Friction Dynamic |
D1894
|
<3
m/min
<10 ft/min
|
0.4
|
| Thermal
Properties: |
| Melting
Point |
DTA,E-168
|
ƒC
(ƒF)
|
267
(512)
|
| Upper
Service Temperature (20,000 hr) |
UL-746B
|
ƒC
(ƒF)
|
150
(302)
|
| Flame
Rating** |
UL-94
|
--
|
VO
|
| Limiting
Oxygen Index |
D2863
|
%
|
30
|
| Heat
of Combustion |
D240
|
Btu/lb
|
6,100
|
| Electrical
Properties: |
| Dielectric
Constant |
D150
|
1 Mhz
|
2.6
|
| Dissipation
Factor |
D150
|
1 Mhz
|
0.005
|
| Arc
Resistance |
D495
|
sec
|
75
|
| Volume
Resistivity |
D257
|
Ohm-cm
|
10
|
| Surface
Resistivity |
D257
|
Ohm/sq
cm
|
10
|
| General
Properties: |
| Weather
Resistance |
Florida
Exposure
|
Years
Unaffected
|
5
|
| Chemical/Solvent
Resistance |
D543
|
--
|
Excellent
|
| Water
Absorption-24 hr |
D570
|
%
|
<0.007
|
*Typical
values are unsuitable for specifications. Properties were measured at
23ƒC (73ƒF), unless otherwise noted.
**Statements regarding behavior in a flame situation are not intended
to reflect hazards presented by this or any other material when under
actual fire conditions.
Tefzel
Fluoropolymer Resin
Replacement of fluorine in fluorocarbon polymers is only commercially
successful when the fluorine is replaced by hydrogen or hydrogen and
chlorine. However, the resulting polymers have significantly different
properties from those of fully fluorinated resins.
When this substitution occurs by regular alternation, polarity and
mechanical properties are maximized. The polymerís polarity increases
because the substituting elementsñhydrogen and chlorineñhave different
electronegativities relative to fluorine. Also, the length of their
bonds to carbon of the polymer backbone differ. Thus, the centers
of electronegativity and electropositivity are not balanced between
chains. The increased interpolymer chain attraction results in higher
mechanical properties. In addition, the increased polarity/interpolymer
attraction influences penetrantsí permeation of the resinís amorphous
component.
However, the presence of hydrogen or of hydrogen and chlorine sacrifices
chemical and thermal stability. For example, in simple molecules,
the C-H bond is ~5 percent weaker than the C-F bond, and the C-C1
bond is 25 percent weaker.
In addition to weak chemical bonds, the arrangement of the substituting
elements along the polymer chain has a marked effect on the resinís
chemical stability. In this regard, solubility can be a leading indicator.
|
Tefzel,
with a regularly alternating structure of the monomers tetrafluoroethylene
and ethylene, has no known solvent in ordinary conditions. In contrast,
polyvinylidene fluoride, the chemical isomer of Tefzel, is soluble
in common industrial ketones (e.g., methyl ethyl ketone). Ethylene/trifluoroethylene
is soluble in some fluorinated solvents. The substituted polymers
are also adversely affected by strong acids and alkalies. Of the three
mentioned, Tefzel is compatible with the broadest range of chemicals
under a wide range of conditions.
Equal proportions of the comonomers react to produce a polymer where
individual monomers alternate regularly along its chain.
Typical properties of Tefzel appear in Table
2. Data in Table 2 and Table
1 show that the polarity and accompanying interpolymer chain
attraction enhance the physical properties of the substituted polymer
over those of the unsubstituted, fully fluorinated polymer. Note,
for example, that Tefzel has about 1.5 times greater strength than
and 2 times greater stiffness.
Summary and Conclusion
The chemistry and physicochemistry inherent in the fully fluorinated
polymer structures allow FEP and PFA fluorocarbon resins
to provide unique resin component benefits for chemical corrosion
resistance. Tefzel fluoropolymer resin comes closer to than
any other partially fluorinated resin, in chemical and electrical
properties, while providing enhanced mechanical ruggedness and economical
processing. |
|
