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257
general reference
About Rotor M aterials
A variety of polymeric composites have been
developed to meet a variety of customer
requirements for rotors, since no single material
will perform satisfactorily in all situations. This brief
summary of each polymer’s particular features and
potential drawbacks is provided to allow the user to
make a more informed valve selection. Consult our
technical specialists for any additional questions.
VICI polymer composites are proprietary formulations:
only the generic compound class can be discussed.
The specifications in the following discussions are
for two position valves. Multiposition selectors
generally have lower pressure and temperature
limits due to the more complex seal design. Actual
specifications for each valve series are shown
on the appropriate pages throughout the valve
sections of the catalog. If a valve is to be used at
a pressure higher than the given standard, please
contact the factory for ordering information.
Valcon E
A polyaryletherketone/PTFE composite, the
E material receives wide GC use in what had
previously been a problematic gap between the
optimum temperature ranges of P and T, and
in HPLC applications where the temperature
requirement is higher than what can be handled
by the H material and where a lower pressure
limit can be tolerated. (Standard specs are 400
psi at 225°C, but higher pressure ratings are
possible at reduced temperatures.) However, this
polymer cannot be used in prolonged contact
with high concentrations of sulfuric and nitric
acids, DMSO,THF, or liquid methylene chloride.
Valcon E2
A proprietary reinforced TFE composite,Valcon E2
works well at lower pressures and is suitable for
temperatures up to 75°C. This material is resistant
to most chemicals but should not be used in
prolonged contact with high concentrations of
sulfuric and nitric acids, DMSO, or liquid methylene
chloride.
Valcon E3
This designation indicates a proprietary polyimide
blend with chemical properties similar to Valcon T,
but with higher compressive strength.
Valcon H
This composite, a carbon fiber reinforced, PTFE-
lubricated inert engineering polymer, has long been
the standard for typical HPLC applications in which
pressures are around 5000 psi and temperatures
are not more than 75°C. It is not unusual for these
valves to be ordered for use at 7000 psi, and less
frequently for use at 10,000 psi. However, at that
point the lifetime may be shortened by as much as
50%.
Valcon H is the rotor material used in the W and UW
series, where no rotor material letter is added (as:
C10W or AC6UW).
Valcon
M
This material, basically a hydrocarbon in structure,
is the most impermeable to light gases of all the
rotor materials currently available, with wide
acceptance in low-temperature (50°C maximum)
trace gas applications. Avoid use with aromatic
hydrocarbons.
Valcon P
This composite, the majority of which is PTFE
and carbon, was the standard choice for most GC
applications before the development of Valcon E.
(Standard specs are 400 psi at 175°C.) Routinely
used at 1000 psi, 75°C, it can also be used at
temperatures approaching 200°C with decreased
sealing tension; however, at that point Valcon E is
probably a better choice from a lifetime standpoint.
Valcon E can replace P in most applications.
Valcon R
While rarely used today,Valcon R (a PTFE
composite) still finds use in low temperature/
pressure situations which require its nearly
universal chemical inertness. Of the chemicals
encountered in commercial practice, only molten
sodium and fluorine at elevated temperatures
and pressures produce any detrimental effects.
Its most severe limitation is that it cannot go over
75°C, even at only 400 psi.
Valcon T
This polyimide/PTFE/carbon composite has been
used successfully for many years and still cannot be
surpassed when applications demand operating
temperatures in the 250°C – 350°C range. (Standard
specs for most series are 300 psi at 330°C.) However,
at temperatures below 150°C there is a tendency
for the seal material to stick to the valve body,
making the valve difficult to turn and causing the
rotor to crack in extreme cases. Literature provided
at the time of purchase contains instructions for
reconditioning the material if this condition should
arise. The T material is susceptible to attack from
steam, ammonia, hydrazines (anhydrous liquids
or vapor), primary and secondary amines, and
solutions having a pH of 10 or more. Chemical
reagents which act as powerful oxidizing agents
(nitric acid, nitrogen tetroxide, etc.) must also be
avoided. Valcon T can be used in “hot”GPC/SEC
applications with O-dichlorobenzene as a solvent.
Valcon TF
This is the series designation for a valve with a
virgin PTFE seal. Its mechanical characteristics
are poor compared to the other choices, but
occasionally its use is dictated by the presence of
oxidizing agents too strong even for the R material.
CHROMalytic TECHnology Pty Ltd AUSTRALIAN Distributors e-mail:
Tel: 03 9762 2034
