PTFE Tube Properties

The Steel Industry and Chemical Processing Industry have been using fluoropolymer tubing products from materials like PTFE and hoses for many years for transferring highly caustic or corrosive chemicals. More and more, PTFE tube is replacing carbon and other metal piping that deteriorates rapidly. Now and for the future, PTFE will continue to serve the industry in critical applications.

THERMAL QUALITIES:

PTFE tubing can withstand temperatures up to 680 °F for limited periods of time.* Under cryogenic conditions, PTFE remains strong down to -320 °F.

*Above 500 °F, mechanical properties become a limiting factor

ELECTRICAL QUALITIES:

PTFE tubing has superb electrical properties, indicated by a low dielectric constant of 2.1 between -40 °F and 480 °F within a frequency range of 5 Hz to 10 GHz.

PTFE tubing is also an excellent insulator with surface resistivity of 3.6 X 1012 ohms (even at 100% relative humidity).

Short time dielectric strengths range from 500 volts/mil (1 mil = 10-3 in) for thicknesses greater than 100 mils to 4000 volts/mil for very thin films.

UV AND RADIATION QUALITIES:

PTFE tubing has excellent UV resistance and weatherability, with a radiation dose threshold for PTFE at 2 – 7 X 104 rads. Absence of oxygen increases radiation resistance by a factor of at least 10.
*Resistance to electron and gamma radiation is relatively poor

WEAR AND FRICTION QUALITIES:

PTFE tubing has a relatively slippery and smooth surface, with a static coefficient of friction of 0.08 and 500 psi load.

The PTFE properties make it particularly suitable for use as bearing pads, under high pressure-low velocity load conditions. Examples are bridge bearing pads, pipe support pads, and mounting pads for heavy manufacturing.

Source:https://www.sukoptfe.com/ptfe-tube-properties

PTFE Hose

PTFE unique properties:

- Excellent chemical resistance. It does not dissolve or swell in any of known solvents. It is resistant to highly aggressive acids and bases. Only very few, very rare substances (fluorine, boiling alkali metals, oxygen bifluoride, chlorine trifluoride) can affect PTFE.
- Wide range of thermal resistance. PTFE remains flexible even at the temperature of liquid helium (-269°C).
Crystalline melting point of PTFE is +327°C, and at +415°C decomposition of PTFE takes place. Working temperature for hoses made of PTFE usually ranges from -70°C up to +260°C depending on the hose design (pressure and mechanical parameters of PTFE start to decrease when the temperature rises above +130°C).
- Resistance to ageing and weather conditions. PTFE is hydrophobic, entirely resistant to ozone, oxygen, light and UV radiation. Samples exposed for several dozen of years to diverse climate conditions have not shown any changes to PTFE properties.
- PTFE has a very low coefficient of friction (from 0.02 to 0.2) and a low value of surface energy. Therefore hoses made of PTFE have self-cleaning properties (substances do not stick to hose walls) so the transfer is very hygienic.
- Good electrical properties, high resistivity.
- Self-extinguishing properties.
- Moderate resistance to abrasion.

Other materials similar to PTFE

Hoses can be manufactured not only from PTFE but also from PTFE copolymers. They usually feature high chemical and thermal resistance but other properties are slightly different in comparison to PTFE (better mechanical resistance, better processing qualities):

- FEP (teflon FEP, DuPont),
- PFA, MFA (teflon PFA, DuPont),
- ETFE (Tefzel, DuPont),
- ECTFE (Halar).

Production and construction of PTFE hoses

Because of high viscosity even at temperatures close to thermal decomposition (+415°C), PTFE hoses are manufactured by extruding the compound of lubricant (paraffin oil) and PTFE powder.

Types of PTFE hose construction:

- Smooth and corrugated hoses with no braid. Used for low pressure applications. Translucent, PTFE wall allows the visual control of the flow.
- Smooth hoses with a single or double external braid made of stainless steel. Widely used for almost all media: chemicals, gases, steam, oils, lubricants, fuel, paint, adhesives, foodstuffs in all branches of industry. The combination of relatively high working pressure of the hoses (up to around 400 bar) and PTFE unique properties
result in a universal and irreplaceable solution for recent industrial technology.
- Corrugated hoses with external braids made of stainless steel or different materials. Sometimes reinforced with a steel wire helix between PTFE and the external braid. Manufactured in various construction options with lower working pressure but higher flexibility than smooth bore hoses.
- Smooth bore hoses with an extruded PTFE liner with a textile braid, steel wire helix reinforcement and an external layer made of rubber. All layers are vulcanized and permanently integrated with the PTFE internal layer - as in a standard rubber hose. Used mainly in chemical industry.

Applications of PTFE

PETROCHEMICAL AND CHEMICAL PROCESSING

PTFE is the material of choice for gaskets, vessel linings, pump interiors, washers, rings, seals, spacers, dip tubes and well-drilling components because it is corrosion resistant and chemically inert; it is unaffected by virtually all acids and caustics and functions in environments to 500 degrees F.

ELECTRICAL APPLICATIONS

PTFE is one of the best insulators known. In thin sections, it will insulate to 500 volts per mil. There are grades of PTFE which have even greater dielectric strength. It is frequently used in wire and cable wrap, and to separate conductive surfaces in capacitors. Thick walled close-tolerance extruded tubing is the PTFE shape of choice where machining or drilling long lengths to close tolerances is impossible. Multi-hole tubing can be extruded. PTFE can be machined into standoff insulators, and many different types of high voltage encapsulation devices for electrical components.

SEMI-CONDUCTOR INDUSTRY

PTFE is inert, and its operating temperature range is from minus 350 degrees Fahrenheit to 550 degrees Fahrenheit. When made to ultra pure standards it is the material of choice for various items used in chip manufacturing, including encapsulation devices for quartz heaters, and the like.

FOOD, BEVERAGE AND PHARMACEUTICAL INDUSTRIES

Virgin PTFE is approved by the Food and Drug Administration for use in the food, beverage, cosmetics and pharmaceutical industries. Thin Film and sheets make an inert, no-toxic slide surface without microscopic depressions where microbes can grow. Conveyancing components - profiles, guide rails and slides - can withstand high temperatures inside baking and drying ovens and other heated segments of the food, cosmetics or pharmaceuticals manufacturing processes.

LABORATORY APPLICATIONS

PTFE tubing,piping and vessels are used in various laboratory ware because of their chemical resistance, and inertness. No contaminants adhere to the surface.

BEARING PADS

Glass filled PTFE can be cut or stamped into bearing pads, and will resist all weather-related degradation while remaining an inert interface between disparate construction materials, like steel and concrete.

PTFE COMPOUNDS

Various fillers can be blended with the PTFE base resin to enhance certain properties, e.g. glass fiber, glass bead, carbon, graphite, molybdenum disulfide, bronze, etc.

Source:https://www.sukoptfe.com/applications-of-ptfe

PTFE Properties

PTFE has excellent properties such as chemical inertness,heat resistance (both high and low), electrical insulation properties, low coefficient of friction (static 0.08 and dynamic 0.01), and nonstick property over a wide temperature range (260 to þ260 C). It has a density in the range of 2.1e2.3 g/cm3 and melt viscosity in the range of 1e10 GPa persecond. Molecular weight of PTFE cannot be measured by standard methods. Instead, an indirect approach is used to judge molecular weight. Standard specific gravity (SSG) is the specific gravity of a chip prepared according to a standardized procedure. The underlying principle is that lower molecular weight PTFE crystallizes more extensively, thus yielding higher SSG values.

PTFE that has not been previously melted has a crystallinity of 92e98%, indicating a linear and nonbranched molecular structure. Upon reaching 342 C, it melts changing from a chalky white color into a transparent amorphous gel. The second melting point of PTFE is 327 C because it never recrystallizes to the same extent as prior to its first melting.

First-order and second-order transitions have been reported for PTFE. The transitions that are close to room temperature are of practical interest because of impact on processing of the material. Below 19 C the crystalline system of PTFE is a nearly perfect triclinic. Above 19 C, the unit cell changes to hexagonal. In the range of 19e30 C, the chain segments become increasing disorderly and the preferred crystallographic direction disappears, resulting in a large expansion in the specific volume of PTFE (1.8%) which must be considered in measuring the dimensions of Marticles made from these plastics.

PTFE is by far the most chemically resistant polymer among thermoplastics. The exceptions include molten alkali metals, gaseous fluorine at high temperatures and pressures, and few organic halogenated compounds such as chlorine trifluoride (ClF3) and oxygen difluoride (OF2). A few other chemicals have been reported to attack PTFE at or near its upper service temperature. PTFE reacts with 80% sodium or potassium hydroxide and some strong Lewis bases including metal hydrides.

Mechanical properties of PTFE are generally inferior to engineering plastics at the room temperature. Compounding with fillers has been the strategy to overcome this shortage. PTFE has useful mechanical properties in its use temperature range.

PTFE has excellent electrical properties such as high insulation resistance, low dielectric constant (2.1), and low dissipation factor. Dielectric constant and dissipation factor remain virtually unchanged in the range of 40 to 250 C and 5 Hz to 10 GHz. Dielectric breakdown strength (short term) is 47 kV/mm for a 0.25-mm-thick film. Dielectric breakdown strength is enhanced with decrease in voids in PTFE, which is affected by the fabrication process.
PTFE is attacked by radiation, and degradation in air begins at a dose of 0.02 Mrad.

Source:https://www.sukoptfe.com/polymer-properties-of-ptfe

Teflon PTFE Tubing Production Show (Dia 20mm-150mm)

PTFE Teflon Tube/Pipe,Rod,Sheet,Film,Seals,Parts...Supplier & Manufacturer - http://www.sukoplastic.com

Vertical Ram Extruder for PTFE tube;Ram extruding machine for PTFE tube;Using for Pre-sintering PTFE material;Suit for new PTFE material or Recycle PTFE material;Rangeof diameter PTFE Extrusion 20-150 mm, Heating zones 5 zones; Automatic.

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