Round Rod in PEEK MD 3000 mm gray

PEEK MD is PEEK with molybdenum disulfide blended in. The additive lowers the friction against steel and raises the wear resistance, while you keep the chemical resistance and heat resistance of the PEEK base. The density is 1.49 g/cm³, slightly heavier than standard PEEK because of the lubricant content.

The round rod is used mainly when you turn parts that will run against metal, often without lubricant or with dry running as the operating mode. Typical applications are plain bearings, shaft bushings, guide sleeves, cam discs and small gears in machines that run hot. The material takes 260 degrees long term and up to 300 degrees short term, which makes it useful in environments where PA, POM or PTFE blends are not enough. The difference from unreinforced PEEK shows up above all in two situations: when the mating part is steel and there is no external lubrication, and when the part has to run at temperatures around 150 to 200 degrees for a long time without wearing out too fast.

Mechanically the tensile strength is around 111 MPa and the ball indentation hardness 260 N/mm². The additive lowers the tensile strength by a percent or so compared with pure PEEK, but the hardness goes up and the wear on the mating part drops clearly. The impact strength is good, around 72 kJ/m² on an unnotched specimen, which means the rod takes a fair number of knocks without cracking. The notched impact strength is fairly low, as with all PEEK, so avoid sharp inward corners in the machining and always leave a small radius in the inner edges when you design the part.

Chemically PEEK MD stands up to most solvents, oils, acids and bases at normal concentrations. It is concentrated sulfuric acid and nitride bearing solutions that bite. The water absorption is low, about 0.03 percent, so the part keeps its dimensions even in damp environments and in hot water up to close to 200 degrees. The fire rating is V-0 without added flame retardants, and the material smokes little in a fire. The thermal conductivity is 0.27 W/(m·K) and the specific volume resistivity is high, around 1·10¹⁴ ohm·cm, which makes the material useful even where insulation is combined with mechanical load.

In machining, PEEK MD behaves like a softer PEEK. Use sharp carbide tools, moderate feeds and plenty of cooling to keep the heat down in the chip zone. When turning long, slender parts thermal drift occurs, so rough turn first and let the rod cool before finish turning to size. Annealing before final machining is worth recommending when the tolerances are tight, since it releases internal stresses from the extrusion. For drilling deep holes, peck drills with good flushing are the best choice, otherwise there is a risk that the chip melts and is dragged into the hole wall.

The rod comes in a number of standard diameters from about 6 mm up to 100 mm, and in standard lengths around 1000 mm. The natural color is beige gray, a little darker than pure PEEK because of the molybdenum disulfide. If you need longer or shorter than the stock length we can cut to size. For small series and design support we are glad to help you choose between PEEK MD, PEEK MG and pure PEEK based on what the part has to do and which mating part it works against. The rule of thumb runs roughly like this: pure PEEK when you want the highest toughness and the best chemical resistance, PEEK MD when the part has to run against steel without lubricant, PEEK MG when you want the lowest coefficient of friction and the highest PV value in the application.

In series production PEEK MD also gives longer tool life than unreinforced PEEK grades in certain kinds of cold forming or deformation, because the wear on the mating part is reduced. That effect matters in applications where the part is to be fitted with a press fit or where it works together with wear resistant steel components. For guide sleeves in hydraulic and pneumatic cylinders PEEK MD is often a good choice, both because the wear on the mating part is kept down and because the hot water resistance allows cleaning and sterilization when needed. In the same way PEEK MD works well in sealing rings and guide elements in compressors, where the material has to take both continuous heat and varying pressure.

When choosing a diameter, allow a margin above the finished size matching the machining required. Smaller series can often be run in a diameter larger than necessary if that is what is held in stock, which saves both time and freight cost. For larger series or particularly long parts it usually pays to order the right diameter directly from the extrusion. When producing parts that have to be dimensionally stable within tight tolerances, preheating before final machining is a good step, since it evens out inherent thermal stresses and reduces dimensional drift after the chips come off.

Do you want help choosing a PEEK grade or a quote on cut lengths? Get in touch.