Sheet in PTFE GF10 1000x1000 mm natural

PTFE GF10 is PTFE with ten percent glass fiber. That is a sensible dose: enough to lift the compressive strength and stop cold flow, but not so much that the chemical resistance is seriously affected. For sheets in environments where pure PTFE would creep out of its groove or deform under long term load, GF10 is often the most practical grade to start with. It gives the step up in mechanical strength that bolted flange joints and static seals need, without costing the chemical properties that were the reason to choose PTFE in the first place.

The material has a density around 2.2 grams per cubic centimeter and a pale white to light gray-white tone. The long term temperature sits at about 260 degrees and the material stays usable down to cryogenic levels without turning brittle. The fire rating is V0. The coefficient of friction stays very low, marginally higher than pure PTFE, which makes the glass a compromise well worth paying for when the component has to carry load. The glass fiber also raises the dimensional stability through temperature swings and pulls down the coefficient of thermal expansion, which is valuable in bolted joints that have to take cycles between cold and hot.

Chemically, PTFE GF10 sits close to pure PTFE in resistance. Acids, bases, solvents, ketones, alcohols, chlorinated hydrocarbons; the material is unaffected in the great majority of process environments. The one thing to watch is that the glass fiber is not as resistant to strongly alkaline media as the base is, so for concentrated caustic at high temperature pure PTFE or PTFE with an inorganic filler can be better. The same goes for hydrofluoric acid, which attacks glass but not the PTFE matrix itself. Water absorption is close to zero and the material remains a good electrical insulator even in damp environments.

The sheet format is machined into gaskets, flange washers, slide plates, wear strips, valve seats and chemical tank linings. In process industry it is used for sealing discs between flanges where the combination of chemical resistance and pressure resistance is needed. Slide plates in ovens and in conveyors where hot or aggressive products move is another classic application, as are wear strips in chemical pumps and guide plates in valve bodies. For valve seats in ball valves GF10 is a common choice because it seals tight without flowing out of the seat, and at the same time takes the torque load from process media running back and forth.

Machining is straightforward with sharp shears, a milling cutter or a water jet. The glass fiber is abrasive, so carbide tools last better than HSS. The sheets are punched into gaskets, milled in CNC or cut with a knife depending on thickness. The material is not welded and is not glued in the conventional way, but it can be etched with a sodium based solution for better adhesion where that is needed. When bolting PTFE gaskets the torque should be checked after a hot run, because the material settles somewhat under heat; retightening after the first cycle is good practice. Cutting fluid is not needed, but air cooling keeps the tool edge cool on heavier cuts.

The application decides the thickness. Thin sheets are used for punched gaskets and membranes, medium thicknesses for slide plates and wear strips, thicker ones for turned parts where a block is milled out. PTFE sheets are press sintered, which gives a homogeneous material straight through the thickness, so the surface quality after machining is even on deep milling as well. That is the difference against extruded plastics, where stresses in the surface can sometimes cause trouble during machining.

PTFE GF10 is food approved in its basic form, which is why it is also used as a slide support and a sealing part in the food and pharmaceutical industries. For direct food contact you should always confirm that the specific batch is certified to the current standard, since the requirements vary between FDA, EU and industry specific rules. The sheet also has very good dielectric properties, which makes it useful as an insulator in transformers and in electrical components where chemical or thermal load is a requirement at the same time. Storage is indoors in a normal warehouse environment; PTFE is insensitive to UV, ozone and moisture and needs no special preparation before use.

The sheet at 1000x1000 mm in natural has glass fiber mixed in that stiffens the material and holds the shape better under load.

If you want to compare grades: pure PTFE when minimal friction weighs heaviest, GF10 when you need better dimensional stability without compromising on the chemistry, GF15 or GF25 when the pressure load rises further. Get in touch if you want to talk dimensions or have a specific sealing job.