Hollow Bar in PTFE GF15 1000 mm natural

Tubes in PTFE GF15 are press sintered PTFE with fifteen percent glass fiber. The addition raises the compressive strength and brings the creep down, which is the whole point when you need to make ring shaped parts that have to seal tight under load and hold their dimensions over a long time. The chemical resistance and the low friction from the PTFE base resin are still there; it is the same material underneath, only mechanically reinforced. For seals and sleeves previously made in pure PTFE that crept out of shape after a couple of months, GF15 is usually the answer without having to switch to a completely different plastic family.

The material has a density of around 2.2 grams per cubic centimeter and a pale white to grayish white tone. The long-term temperature sits at about 260 degrees and downward the material goes to cryogenic levels without losing toughness. The flammability rating is V0. The coefficient of friction remains very low, which makes the material suitable for moving components as well despite the glass filling. The thermal expansion is lower than for pure PTFE, which means pieces in bolted joints keep their seal better through thermal cycles and sleeves in metal housings do not lose their grip at temperature swings.

Chemically PTFE GF15 resists in principle everything industry pumps through a pipe: acids, bases, solvents, oils, chlorinated hydrocarbons, alcohols, ketones and ozone. The glass fiber makes the material somewhat more sensitive to strong caustic at high temperature and to hydrofluoric acid; for those media pure PTFE or an inorganically filled grade is a safer choice. Water absorption is negligible and the material keeps its dimensions even in a damp or fully submerged environment. As an electrical insulator it is still among the better engineering plastics on the market.

The tubular format in GF15 is machined into sleeves, seal rings, plain bearings, guide bands, packings, valve bushings and various process components. In chemical plants it is used in valves, dosing pumps and flange joints where both the tightness of the PTFE seal and the low creep of the GF addition are needed. The tubular format is practical when the part is going to be ring shaped and you want to save material compared with turning from a solid round rod. For rings with large outer diameters and moderate wall thicknesses it is also faster machining, since the material already has a hole from the start and you avoid boring out a solid block.

Machining is done on a lathe with carbide tools, since the glass fiber is abrasive. Cutting fluid is not needed but air cooling keeps the tool and the tube wall cool at heavier cuts. A sharp edge and a small feed give a fine surface finish. The material is not welded and not bonded conventionally; etching or mechanical fastening is required for adhesion. When press fitting sleeves in metal the thermal expansion should be counted in so that the fit holds across the whole temperature range. Press sintered tubes have a homogeneous structure straight through the wall, which means finished parts hold their tolerances well even after several operations.

The choice of dimension is governed by the part. A smaller outer diameter and a thin wall suit small seal rings and guide bands, medium tubes suit bushings and plain bearings in pumps and valves, heavy tubes with thick walls suit large process valves and flange parts. The tubes are stored indoors and supported along their whole length so that they do not go oval over time; that matters especially for tubes with a large outer diameter and a thin wall.

PTFE GF15 is food approved in its base form and is used as a sealing and sliding component in the food, beverage and pharmaceutical industry. For direct food contact the specific batch should always be checked against the current certification standard, since the rules differ between the FDA, the EU and various industry specific programs. In chemical processes the tubes are also used as sliding supports inside valve bodies and as guide sleeves for spindles, where tightness and low friction are needed at the same time. As a dielectric insulator the material is among the best on the market, which means GF15 tubes can be used in combined chemical and electrical applications without having to pick a material for just one of the properties.

The available dimensions vary between production batches. For standard sizes there is stock on most common combinations of outer and inner diameter, and for more unusual dimensions press sintering can be ordered against a lead time. It is wise to check the wanted diameter, wall thickness and length before ordering to see what is on the shelf and what has to be ordered.

The 1000 mm hollow bar in natural is glass fiber reinforced and pre-bored, good for dimensionally stable bushings and rings with less waste.

Between the PTFE grades: pure PTFE for minimal friction without a mechanical load, GF10 as a lightly reinforced grade, GF15 when pressure and creep become critical, GF25 at even higher load, and CP25 with carbon fiber when dynamic wear resistance is priority one. Get in touch if you want to talk dimensions, wall thickness or a specific sealing task.