Round Rod in PEI GF30 3000 mm green

PEI GF30 is polyetherimide reinforced with 30 percent glass fiber. The glass fiber gives the material much higher stiffness, lower thermal expansion and better dimensional stability under load than an unfilled PEI grade. As a round rod it is a common choice when a turned or milled part has to carry mechanical load and work hot at the same time. The difference against unfilled PEI shows most clearly in creep over time.

Technically, PEI GF30 shares the core properties of the material group as a whole. Density is around 1.27 g per cubic centimeter. Continuous service temperature is 170 degrees and the material handles down to minus 50 degrees. UL 94 V0 is enough for most fire requirements in enclosures and rail vehicles. The glass fiber reduces creep under load at raised temperature, which is the difference that often decides the material choice. Water absorption is low, around 0.5 percent, and does not affect the dimensions noticeably in a damp environment.

The natural color is green. It comes from the glass fiber in combination with the base resin and is a quick way to tell the grade from unfilled PEI during assembly. The material is still opaque and has an even, firm surface after turning. When a specific color is needed for field marking, pigmented grades are used, but the green tone is PEI GF30 in its natural state.

As a round rod, PEI GF30 is used for bushings, housings, spacers, insulators, support sleeves and small machine parts that have to hold their dimensions when it gets hot. Typical applications are fixtures for soldering and wave soldering ovens, insulator bushings in switchboards working close to maximum temperature, housings in medical equipment that is steam sterilized, and small loaded parts in test equipment where a metal part is needlessly heavy or conducts current in the wrong way. The material is also found in aircraft and rail vehicle interiors where weight and fire rating both have to be handled at once.

Machining calls for sharp carbide or diamond tools. The glass fiber wears an ordinary steel edge down fast and gives raised tool wear even with the right geometry. Moderate cutting speeds, good chip clearance and clean cooling give the best result. When drilling deep holes, do it in steps and clear the chips often. Keep in mind that PEI is stress sensitive to certain aromatic solvents under load, so avoid acetone and methylene chloride both for cleaning and as cutting fluid. For critical tolerances, a gentle stress relieving before final machining can be worth the time.

The rod is supplied in fixed lengths and a number of diameters. Pick a diameter just above the finished dimension to leave room for turning and any final polishing. For larger series, a tighter choice of blank can shorten cycle time and cut waste noticeably. For single parts it is simpler to start from the nearest larger stocked diameter and let the excess turn into chips. Store the blanks dry and at room temperature, and you avoid the moisture pickup and temperature shock that can otherwise give slight movement in the material during the first cut.

If the choice stands between PEI Eco and PEI GF30, the question is usually how stiff and dimensionally stable the material has to be when hot. If maximum stiffness and low shape change under load are needed, GF30 is right. If the part instead has to be easier to machine and carry a more transparent tone, an unfilled grade is better. If the part needs an even higher service temperature, you step up to PEEK or PEKEKK. If stiffness is the only criterion and the machining cost can go up, GF50 is one more step.

In designs that mix plastic and metal, PEI GF30 works predictably with both aluminum and steel. Thermal expansion is lower than for unfilled PEI and keeps fits stable through temperature cycles. For press fitting of insert bushings the material performs well, as long as the hole is dimensioned with margin for the glass fiber. Bonding suits polar epoxy systems after a light surface activation. When assembling with screw and washer, a moderate tightening torque is recommended, since high point load can give micro cracks at the edge of the drilled hole. For critical bolted joints, metal threaded inserts or sleeves are preferred, since they spread the load over a larger area in the material and reduce the risk of creep at operating temperature.

Green glass fiber reinforced PEI rod at 3000 mm, for turned parts that have to hold still in their dimensions when hot. The glass fiber makes the rod stiffer than the unfilled one.

Are you unsure about the right grade or dimension? Get in touch, we will help you match the material against operating temperature, load and machining.