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Properties of Valve Rotor Materials
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CTFE
Valcon E
Valcon E2
Valcon H
Valcon M
Valcon P
Valcon R
Valcon T
Valcon TF
Valcon X
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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 valves
generally have lower pressure and temperature limits due to the more complex seal design.
Actual specifications for each valve series are shown with the valve discussions. If a valve is to be
used at a pressure higher than the given standard, please contact the factory for ordering
information.
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CTFE
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Chlorotrifluoroethylene, is the generic name for the material produced as Kel-F ® and as Aclar
®. It is very resistant to all chemicals except THF and some halogenated solvents, and can be
used at temperatures up to 100°C. Swells in ketones.
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Valcon E
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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.
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Standard rotor for:
Valco GC medium temp valves; all
Valco multiposition valves (except 1/4").
Cheminert HPLC injectors and valves with PAEK stators (both two
position and multiposition)
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Valcon E2
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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.
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Standard rotor for:
Valco 1/4" low pressure multiposition valves (stream
selectors).
Cheminert low pressure valves (ZDV and 1/4-28) and stream
selectors (except 1/2-20 fittings)
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Valcon H
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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%.
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Standard rotor for:
Valco HPLC injectors and switching valves.
Cheminert HPLC injectors and valves with metal stators (both two
position and multiposition)
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Valcon M
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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.
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Valcon P
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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.
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Valcon R
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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.
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Valcon T
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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.
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Standard rotor for:
Valco GC high temp valves.
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Valcon TF
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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.
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Standard rotor for:
Cheminert stream selectors with 1/2-20 fittings for 1/4" tubing.
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Valcon X
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This designation indicates a proprietary polyimide blend with
chemical properties similar to Valcon T, but with higher
compressive strength.
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