PTFE Properties & PTFE Product Processing

PTFE is a thermoplastic polymer, which is a white solid at room temperature, with a density of about 2200 kg/m3. It maintains high strength, toughness and self-lubrication at low temperatures down to 5 K (−268.15 °C; −450.67 °F), and good flexibility at temperatures above 194 K (−79 °C; −110 °F). PTFE gains its properties from the aggregate effect of carbon-fluorine bonds, as do all fluorocarbons. The only chemicals known to affect these carbon-fluorine bonds are highly reactive metals like the alkali metals, and at higher temperatures also such metals as aluminium and magnesium, and fluorinating agents such as xenon difluoride and cobalt(III) fluoride.

PTFE Properties & PTFE Product Processing

The coefficient of friction of plastics is usually measured against polished steel. PTFE’s coefficient of friction is 0.05 to 0.10, which is the third-lowest of any known solid material. PTFE’s resistance to van der Waals forces means that it is the only known surface to which a gecko cannot stick.In fact, PTFE can be used to prevent insects climbing up surfaces painted with the material. PTFE is so slippery that insects cannot get a grip and tend to fall off.

Because of its chemical inertness, PTFE cannot be cross-linked like an elastomer. Therefore, it has no “memory” and is subject to creep. Because of its superior chemical and thermal properties, PTFE is often used as a gasket material within industries that require resistance to aggressive chemicals such as pharmaceuticals or chemical processing. However, because of the propensity to creep, the long-term performance of such seals is worse than for elastomers which exhibit zero, or near-zero, levels of creep.

Processing PTFE can be difficult and expensive, because the high melting temperature, 327 °C (621 °F), is above the initial decomposition temperature, 200 °C (392 °F). Even when melted, PTFE does not flow, but instead behaves as a gel due to the absence of crystalline phase and high melt viscosity.

Some PTFE parts are made by cold-moulding, a form of compression molding. Here, fine powdered PTFE is forced into a mould under high pressure . After a settling period, lasting from minutes to days, the mould is heated at 360 to 380 degrees Celsius , allowing the fine particles to fuse into a single mass.

Post time: Jun-18-2020