LUVOCOM 3F PEI 50236 GY is a grey polyetherimide compound formulated for fused filament fabrication and other extrusion-based additive manufacturing operations. The grade belongs to the LUVOCOM 3F series, which is compounded for the rheological and thermal requirements of layer-by-layer deposition rather than for conventional injection moulding. The polyetherimide base resin is amorphous, with a glass transition temperature measured by ISO 11357-2 in the region of 215 °C to 217 °C. The designation 50236 GY identifies a filled, grey product; the filler package increases stiffness and reduces elongation compared with unfilled PEI, while retaining electrical insulation. The product is used for high-temperature fixtures, manifold prototypes, covers, and electrical housing parts where continuous exposure above 160 °C and dimensional stability under load are specified. Published data for this exact configuration should be verified against the manufacturer’s certificate of analysis; however, filled PEI compounds of this class are typically specified with a density of 1.30–1.38 g/cm³ under ISO 1183-1 and a tensile modulus of 3.8–5.5 GPa under ISO 527-2.

In comparison with unfilled PEI, the product reduces thermal expansion and improves creep resistance in printed sections, but the trade-off is a lower elongation at break and increased notch sensitivity. Against a carbon-fiber-filled PEI, the grey grade avoids conductive surfaces and is therefore used where dielectric properties or colour contrast are more important than maximum stiffness. Relative to semi-crystalline PEEK, the amorphous PEI shows lower anisotropic Z-direction shrinkage but lower continuous-use temperature and chemical resistance. These differences govern material substitution on existing tooling: the build chamber, nozzle, and bed set points must be changed from lower-temperature amorphous polymers such as ABS or polycarbonate, and the printer must be capable of stable operation in the 360 °C to 380 °C hot-end range.

The “3F” designation indicates the product family intended for filament-based additive manufacturing; the suffix 50236 is an internal material code that captures the filler system and viscosity target, while “GY” denotes grey. Unlike standard injection-moulding PEI grades that are supplied as pellets for direct plastication, this product is subjected to additional stabilisation and rheology modification so that repeated heating in an FFF hot end does not produce the same molecular-weight loss profile as a single-shot injection cycle. The grade is therefore specified for applications where the printed part will be heated a second time during post-processing, such as annealing, adhesive bonding, or embedding of inserts.

In comparison with a carbon-fiber-filled PEI, the glass-reinforced grey product has a lower probability of creating conductive particulate contamination in electrical assemblies. This is relevant for fixtures used near live terminals or for assembly tools in battery production, where a carbon-filled surface can leave a conductive smear. The grey colour also permits automated optical inspection of surface defects more readily than black or dark-coloured high-temperature filaments.

What Drying and Extrusion Parameters Govern Layer Fusion in PEI 50236 GY?

Moisture control is the first processing boundary. Polyetherimide absorbs atmospheric moisture, and residual moisture above 0.02 % drives hydrolysis in the melt. The result is molecular-weight loss, a lower melt viscosity, nozzle drool, surface splay, and reduced interlayer peel strength. Drying is performed at 150 °C for 4–6 h in a dehumidifying dryer with a dew point of -40 °C or lower. Moisture content is confirmed by Karl Fischer titration or ISO 15512. Dried feedstock exposed to plant air above 30 % relative humidity for more than 30 min should be re-dried before use.

For continuous printing cells, the material is fed from a sealed dry-feed system that maintains the environment below -20 °C dew point. If a machine uses a filament spool exposed to room air, the filament should be dried in a vacuum oven or desiccant dryer and then stored in a sealed container with fresh desiccant. The moisture uptake rate is highest in the first 60 min of exposure, especially in plants where relative humidity exceeds 60 %. A filament spool that has been left unprotected overnight should not be processed without re-drying, even if the surface appears dry.

The extrusion window is narrow. At nozzle set points below 360 °C, melt viscosity is high enough to limit interlayer diffusion and produces a weak fusion plane. At set points above 380 °C, chain scission and outgassing increase. The build chamber should be maintained at 90 °C or higher; the build platform should be held at 140 °C to 160 °C. On production-scale machines with thermocouple-verified hot ends, a set-point deviation of 5 °C has been observed to shift large parts from acceptable fusion to delamination at Z-height transitions above 80 mm. A nozzle diameter of 0.4–0.8 mm with a layer height of 0.15–0.25 mm is used for most structural applications; a larger nozzle above 0.8 mm raises throughput but requires longer melt residence time and more controlled heating because the temperature gradient across the melt stream can develop a cold core.

The shear-thinning response of the compound is evaluated by capillary rheometry according to ISO 11443, with a die length-to-diameter ratio of 20:1 to minimize entrance-pressure error. During FFF deposition through a 0.4 mm nozzle at typical print speeds of 30–60 mm/s, the apparent shear rate in the nozzle lands can exceed 500 s⁻¹. The grade is compounded to sustain melt strength at these shear rates without excessive die swell; excessive die swell in a filament path changes the effective bead width and reduces dimensional accuracy. In production trials, a melt-viscosity shift of ±10 % can require first-layer offset compensation of 0.03–0.05 mm to maintain the target bead width.

First-layer printing is performed at a reduced speed of 15–25 mm/s and a first-layer bed temperature at the upper end of the range. If the first layer is printed too cold, the solidified bead can lift from the bed and create a wedge-shaped gap that propagates into a delamination plane. If the first layer is printed too hot and the bed is above 165 °C, the part can become difficult to remove from the print surface or can show an upset edge. The use of a sacrificial adhesion layer such as PEI film or polyimide tape is standard; the surface should be cleaned with isopropanol and dried before heating.

Storage and incoming-material control follow the same hygroscopic logic. Once a container is opened in a plant ambient above 60 % relative humidity, the remaining feedstock is re-dried before the next build. At the compounding stage, a twin-screw extruder with an L/D ratio between 36:1 and 44:1 is used to disperse the filler and pigment package. Melt flow rate testing under ISO 1133-1:2022 and tensile testing on printed ISO 527-2 type 1BA coupons provide incoming acceptance data. An upward shift in MFR above the specified range for the grade indicates moisture abuse or molecular-weight degradation, and such material is excluded from load-bearing or thermally cycled parts.

Incoming inspection of the filament diameter is performed by laser micrometry along the spool length. A diameter variation greater than ±0.05 mm from the nominal value can produce over-extrusion or under-extrusion in the melt zone, particularly on direct-drive extruders with short melt chambers. The ovality of the filament should be below 0.05 mm; a roundness defect can rotate in the feeder and cause periodic bead-width errors.

Mechanical, Thermal, and Electrical Baseline Comparisons

Table 2 supplies class-level values for glass-fiber-reinforced PEI materials of this product grouping. These values are not substitutes for the batch certificate, but they are useful for initial design comparison against unfilled PEI and carbon-fiber PEI.

When a printed section is thinner than 3 mm, the Z-direction tensile strength is typically 50–70 % of the X-Y value because layer interfaces are the limiting structural feature. This ratio is not a material defect but an additive-manufacturing boundary. To reduce stress concentration, internal fillets with a minimum radius of 2 mm and wall-thickness transitions no steeper than 1:3 are used. Annealing at 200 °C for 2 h with a controlled ramp of 0.5–1.0 °C/min can reduce deposition stress in small parts; large or thick sections require support tooling because creep distortion can occur above the glass transition. Published data for the annealing response of this specific configuration is limited, so first-article trials are required before production release.

The test values in Table 2 are equilibrium or ambient values. At continuous service above 160 °C, the tensile modulus of the printed material decreases and creep rates increase; finite-element models should therefore use time-temperature superposition data if the part is under sustained load. For short-term exposure, the material retains usable stiffness up to the heat deflection temperature, but long-term dimensional stability is not directly obtained from ISO 75-2 because the method applies a constant flexural stress for a short ramp period.

For large-format machines with build volumes above 500 mm in the longest axis, the achievable dimensional stability is influenced by the thermal uniformity of the chamber. A chamber gradient of 10 °C across a 500 mm build envelope can produce differential shrink at the edges of a flat tooling plate. Therefore, large PEI builds are often produced with a brim and a controlled cool-down phase below 140 °C before part removal. Field observations on production-scale machines show that removing a large PEI part from a heated bed above 120 °C can cause immediate warping or delamination at the base corners; the part is cooled to below 90 °C under the chamber before opening the door.

When Breakaway Support Removal Coincides with Chemical Exposure Limits

The filled grade has a lower elongation at break than unfilled PEI, and this increases notch sensitivity at the interface between the part and breakaway support. The support interface layer should be generated at 0.1–0.2 mm with a separation angle no steeper than 45° to reduce peel force. After support removal, microcrack inspection under 10× magnification or dye-penetrant testing according to ASTM E1417 is used for load-bearing parts. Solvent-based support removal with chlorinated solvents or aromatic hydrocarbons is not recommended because the amorphous PEI can undergo environmental stress cracking when deposition stress is present. If a soluble support system is unavoidable, the solvent must be validated against the final printed geometry and operating stress; published compatibility data for this exact filled PEI configuration is limited.

In chemical service, unstressed PEI generally withstands aliphatic hydrocarbons, alcohols, and dilute mineral acids at ambient temperature. Concentrated sulfuric acid, halogenated solvents, ketones, and strongly alkaline solutions above pH 9 at elevated temperature attack the polymer. Printed parts that will carry mechanical load in a chemical environment are screened by immersion at the maximum service temperature for 7 days; this screening is not a substitute for long-term validation. Electrical insulation behaviour is characterized by volume resistivity according to IEC 62631-3-1, but the measured value on a printed plaque is lower than on a solid injection-moulded plaque because layer lines and microvoids reduce the effective dielectric thickness. Regulatory status is assessed under RoHS Directive 2011/65/EU and delegated directive (EU) 2015/863, while REACH obligations under 1907/2006/EC apply to the feedstock and the finished article. The printed part should not be assumed to satisfy food-contact or medical-grade requirements unless a specific compliance statement has been issued by the manufacturer for the exact grade, colour, and final surface finish.

Post-print machining uses carbide or polycrystalline diamond tooling with low cutting speeds because the glass reinforcement and the high glass transition temperature cause tool wear and localized melt at the cut surface. Coolant or compressed air is used to keep the cut surface below 180 °C; overheating produces a smeared, glossy surface that can hide microcracks.