PTFE (Teflon)

Virtually none. PTFE resists every industrial acid, alkali, solvent, oxidiser and most reactive gases at room temperature, and almost all of them at elevated temperatures too. The few materials that attack PTFE are molten alkali metals (sodium, potassium), elemental fluorine at high temperature, and some chlorine trifluoride compounds. For all practical industrial chemistry, PTFE is inert.

Under sustained compressive load, unfilled PTFE will slowly deform (creep) over time, which can loosen gaskets and dimensional parts. Filled grades (glass-filled, carbon-filled, bronze-filled) reduce cold flow significantly and are the right pick for any load-bearing PTFE part. For gaskets, ePTFE (expanded PTFE) carries this same benefit while keeping seal compliance.

Yes. Food-grade PTFE certified to FDA 21 CFR 177.1550 is widely used for food processing seals, chute liners and non-stick conveyor belts. Pigmented food-grade PTFE is also available for visual food contact (blue is common for food-industry traceability).

Standard adhesives will not stick to PTFE because of its non-stick surface. For bonded assemblies the PTFE surface must first be chemically etched with sodium-naphthalene or plasma-treated to create a chemically active surface; etched PTFE then bonds with epoxy or polyurethane adhesives. For most assembly work we recommend mechanical fasteners instead.

PTFE has a continuous service temperature of -200°C up to +260°C, which is the widest range of any common plastic. Short-term peaks to 280°C are tolerated. Above this PTFE begins to decompose and should not be used.

PTFE cannot be welded the way polyolefins can; the polymer chain does not flow at melt temperature. For joining PTFE we use mechanical fasteners, etch-and-bond, or for some applications PTFE sheet can be sintered together at high temperature in an oven (specialist process).

The polymer is more expensive to manufacture than polyolefins (multiple polymerisation steps under fluorine) and the resin density is roughly double, which means more weight per sheet at the same dimensions. PTFE is also harder to machine, so the part cost is higher per piece. For chemical and temperature service where PTFE is the only material that works, the cost is justified.