Teflon

Material Notes

This is the brand name for a number of fluorinated polymers. Teflon is polytetrafluroethylene (PTFE). This is a polymer with repeating chains of –(CF2-CF2)- in it.

Teflon was first discovered by Roy J. Plunkett (1910-1994) in 1938 and introduced as a commercial product in 1946.

Below you can find the most uprising characteristics of this material which makes it useful for tons of industrial and domestic applications in our daily life:

- Resistant to many chemicals
This includes ozone, chlorine, acetic acid, ammonia, sulfuric acid and hydrochloric acid. The only chemicals known to affect these coatings are molten alkali metals and highly reactive fluorinating agents.

- Weather and UV resistance

- Non stick
Very few solid substances will permanently adhere to a Teflon coating. While tacky materials may show some adhesion, almost all substances release easily.

- Outstanding performance at extreme temperatures
In fact it can temporarily withstand temperatures of 260C and cryogenic temperatures of -240C and still have the same chemical properties.
It has an initial melting point of 342C (+- 10C) and a secondary melting point of 327C (+- 10C).

- Low coefficient of friction.
It is the ratio of the force required to make two surfaces slide over each other. A low number equals low resistance and smooth operation. This indicates the difficulty in sliding one surface against another. The coefficient of friction is generally in the range of 0.05 to 0.20, depending on the load, sliding speed, and type of Teflon coating used.

- Non wetting
Teflon finishes are both hydrophobic and oleophobic, cleanup is easier and more thorough.

- Exceptional dielectric properties
Teflon has a high dielectric strength over many different frequencies, low dissipation factor and high surface resistivity. Dielectric strength is the high voltage that the insulating material can withstand before it breaks down. In addition it has a low dissipation factor; this is the percentage of electrical energy absorbed and lost when current is applied to an insulating material. A low dissipation factor means that the absorbed energy dissipated as heat is low.
The high surface resistivity refers to the electrical resistance between opposite edges of an unit square on the surface of an insulating material.

- Excellent optical properties

Market Applications

Products depending on type of application include resins, additives, coatings and films. Market application includes the following:

- Electrical and electronic industry.
For example semiconductor manufacturing. Electronics used as an insulation material or in system components

- Wire and cable for outstanding electrical performance and durability

- Pharmaceutical and Biotech manufacturing

- Metal finishing, paints and coatings
As flour additives can be added to reduce the wear and tear on load-bearing surfaces. For example in inks and lithographic printing, thermoplastics and molded gears, protective industrial surfaces, lubricants to thicken, sterile packaging, etc.

- Optical devices.
It can be used as clear coating for optical devices, requiring a low refractive index and still perform in aggressive chemical environments over a wide range of use temperatures and light waves (UV-IR). Lightweight surgical lamps, photovoltaic cell glazing, etc.

- Automotive uses
Airbag systems, fuel hose permeation barrier, fuel system, chassis, brake systems, oil filter, etc.

- Cabling materials

Chemistry
Structurally, there are different types of Teflon:
- Teflon PTFE resin is a polymer consisting of recurring tetrafluoroethylene monomer units with the formula: (CF2-CF2)n

- The Tetrafluoroethylene Hexafluoropropylene-copolymer FEP: [CF(CF3)-CF2(CF2-CF2)n]m

- Perfluoroalkyoxy-polymers, PFA has the same advantages as PTFE Teflon with the structure: [CF(OR,)-CF2(CF2-CF2)n]m OR, represents a perfluoroalkoxy group.

Mechanical properties (Properties were measured at 23°C (73°F), unless otherwise noted)
Properties Teflon PTFE (Powder,
paste, disper)
Teflon (FEP) Teflon PFA Tefzel
Specific gravity 2.13-2.22 2.15 2.15 1.70-1.78
Tensile Strength
Mpa (psi)
21-35 Mpa (3,000-5,000 psi) 23 Mpa(3,400 psi) 25 Mpa(3,600 psi) 40-47 Mpa (5,800-6,700 psi)
Elongation %
300-500% 325% 300% 150-300%
Flexural Modulus
Mpa (psi)
500 Mpa (72,000psi) 600 Mpa(85,000psi) 600 Mpa(85,000psi) 1,000 Mpa(145,000psi)
Folding Endurance
(MIT) Cycles
>106(MIT)cycles 5-80 x 103 10-500 x 103 10-27 x 103
Impact Strength
J/m (ft.lb/in)
189 J/m (3.5ft·lb/in) No Break No Break No Break
Hardness
Shore D
50-65 Shore D 56 Shore D 60 Shore D 63-72 Shore D
Coefficient of Friction, Dynamic <3 m/min(<10 ft/min) 0.1 0. 0.2 0.23
Thermal properties
Melting point °C(°F) 327 (621) 260 (500) 305 (582) 245-280 (473-536)
Upper Service Temperature (20,000h) °C(°F)

260(500) 204(400) 260(500) 155(311)
Limiting Oxygen Index %
>95 >95 >95 30-36
Heat of Combustion MJ/kg(Btu/lb) 5.1(2,200) 5.1(2,200) 5.3(2,300) 13.7(5,900)
Performance characteristics
Teflon (AF) Teflon (PFA)
Morphology Amorphous Semicrystalline
Optical Clarity Clear: >95% Translucent to Opaque
Upper Use Temperature, °C (°F) 285 (545) 260 (500)
Thermal Stability, °C (°F) 360 (680) 380 (716)
Thermal Expansion (linear), ppm/°C 80 150
Water Absorption No No
Weatherability Outstanding Outstanding
Flame Resistant LOI, % 95 95
Tensile Modulus, MPa (psi) 950–2150 (137,786–311,832) 271–338 (39,305–49,023)
Creep Resistance Good Low
Solubility Selected Solvents No
Resistance to Chemical Attack Excellent Excellent
Surface-Free Energy Low Low
Refractive Index 1.29–1.31 1.34–1.35

Dielectric Constant
1.89–1.93 2.1

Source of information: www.dupont.com
Teflon is the brand name for a number of fluorinated polymers manufactured by EI DuPont de Nemours.

Other useful information about materials and elements properties can be access through the following web-pages:

- Stainless Steel Monel

- Periodic table









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