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What is PCTFE Material?

PCTFE (Polychlorotrifluoroethylene) PCTFE (Polychlorotrifluoroethylene) is a homopolymer of Chlorotrifluoroethylene. PCTFE is a unique fluoropolymer that is capable of maintaining its physical properties at exceptionally low operating temperatures.

PCTFE has excellent chemical resistance, radiation resistance, and flammability characteristics. The material has a useful temperature range of -400°F to 380°F. PCTFE is resistant to cold flow and it has the lowest coefficient of thermal expansion of any unfilled fluoropolymer. These characteristics make it an excellent choice when dimensional stability is critical.

PCTFE is often used for aerospace applications when chemical resistance, a broad operating temperature range, and low flammability are required. It is also extensively used for cryogenic valve applications.

Key Properties of PCTFE Material

• Dimensionally stable, rigid, and resistant to cold flow
• Very low gas permeation and outgassing
• Near zero moisture absorption
• Excellent chemical resistance
• High compression strength
• Low deformation under load
• Non-flammable
• Temperature range: -400° to 380°F
• Radiation Resistance

Property	Value	Units	Method
Tensile Strength	4860 – 5710 34 – 39	psi MPa	D 638
Elongation	100 – 250	%	D 638
Flexural Strength, 73°F	9570 – 10300 66 – 71	psi MPa
Flex Modulus	200 – 243 x 103 1.4 – 1.7	psi MPa
Impact Strength, Izod, 23 deg C	2.5 – 3.5	ft-lb/in	D 256
Compressive Stress at 1% deformation,	1570 – 1860 11 – 13	psi MPa	D 695
Density	2.10 to 2.17	gm/cu.cm
Coefficient of Linear Expansion	7 x 10-5	K-1
Melting Point	410 -414 210 – 212	deg F deg C
Thermal Conductivity	1.45 0.84	Btu·in/h·ft2·°F W/m·K	ASTM C 177
Specific Heat	0.22 0.92	Btu/lb/deg F kJ/Kg/deg K
Heat Distortion Temperature, 66 lb/sq.in (0.455 MPa)	259 126	deg F deg C	D 648
Processing Temperature	620 327	deg F deg C
Dielectric Strength, short time, 0.004”	3000	Volt/mil	D 149
Arc-Resistance	360	sec	D 495
Volume Resistivity, @ 50% RH	2 x 1017	ohm-cm	D 257
Surface Resistivity, @ 100% RH	1 x 1015	Ohm sq-1	D 257
Dielectric Constant, 1 kHz	2.6	ε	D150-81
Dissipation Factor, @ 1 kHz	0.02		D150-81
Water Absorption	0.00	% increase in weight	D570-81
Flame Rating+	Non-flammable		D 635
Coefficient of friction			D 1894
Specific Gravity	2.10 to 2.17		D792
Moisture Permeability Constant	0.2	g/m, 24 hours
O2 Permeability	1.5 x 10-10	Cc, cm/sq.cm, sec, atm
N2 Permeability	0.18 x 10-10	Cc, cm/sq.cm, sec, atm
CO2 Permeability	2.9 x 10-10	Cc, cm/sq.cm, sec, atm

PCTFE Valve Seat

Ball valve seats that show signs of swelling, blistering, or “popcorning” have been permeated at a molecular level. Needless to say, this can cause some serious issues such as leaks and catastrophic failure. The solution is to find a ball valve seat material that is highly resistant to permeation and an excellent choice would be PCTFE. In this week’s blog post, we will talk about PCTFE Ball Valve Seats and how they are used in Low Permeation Applications.

One of the best materials for a ball valve seat application where permeability is a problem would be PCTFE (Polychlorotrifluoroethylene), a thermoplastic chlorofluoropolymer. PCTFE is sometimes referred to as Modified PTFE or PCTFE, as well as by trade names Kel-F, Voltalef, and Neoflon. PCTFE is often thought of as a second-generation PTFE material that maintains the chemical and thermal resistance of PTFE along with its low friction. It is also similar to other fluoropolymers such as PFA or FEP.

One of the defining characteristics of PCTFE is that it has a much more dense molecular structure and a low void and micro-porosity content when compared to similar ball valve seat materials. This gives it a very low permeability coefficient, which means that the likelihood of it swelling or popcorning is far lower than other materials. For example, its permeability for O2, N2, CO2, and H2 are 1.5 x 10-10, 0.18 x 10-10, 2.9 x 10-10, and 56.4 x 10-10 darcy, respectively.

PCTFE also provides improved toughness and strength along with good deformation recovery and excellent creep and cold-flow resistance. In addition, it has a wide operating temperature range of -100°F to 500°F. In fact, it performs extremely well at cryogenic temperatures. Because of its low friction, it also results in a very low ball valve operating torque. PCTFE also exhibits zero moisture absorption and is non-wetting.

PCTFE works well in operating environments where other polymers may fail. For example, it is well adapted to nuclear service that may involve high radiation exposure, is non-flammable (D 635), and is resistant to attack by the vast majority of chemicals and oxidizing agents. The only chemicals that might lead to slight swelling are ethers, esters, aromatic solvents, and halocarbon compounds.