EMS-Grivory Grilamid L 20 G grey 9280 is a semi-crystalline polyamide 12 injection-moulding compound reinforced with nominal 20% by mass glass fibre and supplied in a controlled dry condition. The designation L 20 G identifies the polyamide 12 backbone, the 20% glass-fibre loading and the glass-fibre reinforcement type; grey 9280 is the manufacturer’s colour code. Under ISO 1043-1, the material can be designated PA12-GF20. The term dry is a supply condition rather than a separate chemical grade: moisture content is held below the supplier’s recommended melt-processing limit, typically below 0.10% by mass, to reduce hydrolytic degradation and surface defects. Dry-state mechanical values should be used for mould-filling simulation and initial design, but conditioned values are required where parts reach moisture equilibrium in service.

Because the polyamide 12 backbone has a longer aliphatic segment between amide groups than polyamide 6 or polyamide 66, the material exhibits lower equilibrium moisture uptake. Under ISO 62 at 23°C and 50% relative humidity, a glass-filled PA12 typically absorbs about 0.7% moisture by mass, whereas PA66 grades can absorb 2.0–2.5% under the same exposure. This lower moisture uptake reduces the notched-impact shift between dry and conditioned states and limits the change in volume resistivity that accompanies water absorption. In a glass-reinforced PA12, the penalty is lower short-term heat resistance than PA66: heat deflection temperature under 1.8 MPa is typically below 160°C for PA12 GF20, while many PA66 GF20 grades exceed 240°C. Selection therefore depends on whether the part is moisture-limited or heat-limited.

Mechanical and thermal property envelope in the dry state

The following representative values are taken from the published dry-moulded dataset for glass-fibre-reinforced polyamide 12 and are not specification limits. Lot-specific certificates and colour-dependent data for grey 9280 should be used for qualification.

After conditioning to equilibrium at 23°C and 50% RH, tensile modulus can decrease by approximately 30–40%, while elongation at break and notched impact generally increase. In designs with snap-fits or impact-sensitive features, dry-state notched Charpy data from ISO 179/1eA should not be used alone; the lower end of the conditioned range should also be considered.

What separates a 20% glass-filled PA12 dry-moulding compound from PA6 GF20 and PA66 GF20 in fuel-vapour service?

In comparison with PA6 GF20 and PA66 GF20, the PA12 grade has lower density and lower water absorption but lower tensile modulus and lower heat deflection temperature under load. PA6 GF20 typically delivers a dry tensile modulus above 6,000 MPa, and PA66 GF20 often exceeds 7,000 MPa, while the PA12 grade is commonly near 4,800 MPa. Density is about 1.23 g/cm³, which is below the 1.35–1.40 g/cm³ range common for PA66 GF20. The lower density can reduce mass in valve bodies and cable-management components by approximately 8–12%, although the exact saving depends on wall thickness and tooling.

In fuel and vapour connectors, the larger aliphatic content of PA12 provides better resistance to zinc chloride, fuels, oils and hydraulic fluids than PA66 under many automotive service conditions. The material is not a direct replacement for PA66 in high-temperature coolant housings where continuous hot-air or hot-glycol environments exceed about 100°C under load; for those applications, high-heat grades should be selected.

Compared with unfilled PA12, the 20% glass-fibre system raises tensile modulus from approximately 1,400–1,800 MPa to about 4,800 MPa and reduces mould shrinkage from above 0.8% to approximately 0.3% in the flow direction. The reinforcement also reduces elongation at break from above 200% to about 3%, so the grade is selected for rigidity and dimensional accuracy rather than snap-fit ductility.

Typical production applications for Grilamid L 20 G grey 9280 dry include pneumatic quick-connect couplings, fuel-vapour connectors, cable clips and housings, water-management components, and parts requiring low creep at moderate temperatures. In pneumatic quick-connect bodies, burst-pressure performance should be validated to ISO 14743 on finished parts because the interface between the glass fibre and the PA12 matrix, gate location, and weld-line position control failure mode more than the raw tensile database. Threaded or snap-fit closures in glass-reinforced PA12 should be tested to the applicable assembly torque and cycling specification; dry-moulded parts can show lower ductility at weld lines if mould temperature is below 60°C.

Because the glass fibres orient in the flow direction, shrinkage is anisotropic, and post-mould warpage can appear in plate-like parts with non-uniform wall thickness. Measurement according to ISO 294-4 typically shows flow-direction shrinkage near 0.2–0.5% and transverse shrinkage 0.5–0.8%, depending on mould temperature and gate type. If flatness is critical, mould-temperature uniformity across the cavity should be maintained within ±5°C, and gate location should be selected to produce parallel flow fronts.

When the grade is processed on reciprocating-screw injection moulding machines

The compound should be dried before processing in a dehumidifying dryer at 80°C for 4–6 h, with a dew point of −30°C or lower. If the packaged dry material is exposed to ambient air with relative humidity above 60%, drying is required again because PA12 moisture pick-up at high relative humidity can be rapid. A residual moisture content below 0.10% by mass is recommended before melt processing. Processing from open bags or hoppers without dry-air retention can produce silver streaks, glass-fibre surface bloom and reduced tensile strength at weld lines.

Barrel-temperature settings are commonly distributed from 220°C in the rear zone to 250–260°C at the nozzle, with a melt temperature of 250°C and mould temperature of 60–80°C for dimensional stability. On a 25 mm reciprocating screw with 20:1 L/D and a compression ratio of 2.0–2.5, back pressure is typically kept between 0.5 MPa and 1.0 MPa to avoid excessive glass-fibre breakage. Injection speed is medium to high but should be reduced near the end of fill if gate blush or jetting appears. Hold pressure is adjusted to part mass and gate freeze; values in the range 50–80 MPa are common for small-to-medium connectors.

Hot-runner systems with valve gates are used to reduce gate vestige and to improve cycle time. However, the lower viscosity of PA12 at processing temperatures makes valve-pin opening and closing timing critical; premature opening can produce flow marks, while late opening can create hesitation and fibre-rich layers near the gate. Tool steel should be selected for abrasive glass-fibre wear, and gate inserts of through-hardened H13 tool steel or equivalent are standard for glass-filled grades. Melt residence time above 10 min at 260°C should be avoided; thermal degradation causes yellowing, viscosity drop and loss of weld-line strength.

In the melt, the fibre-length distribution after plastication influences tensile modulus and notched impact. A standard general-purpose screw with a compression ratio of 2.0:1 and a correctly sized check ring may retain fibre length better than a high-shear barrier screw, but homogenisation can suffer at low back pressure. The supplier’s processing data for PA12 GF20 generally recommend a medium-shear screw; high-shear mixing sections should be avoided unless glass dispersion is demonstrated by burn-off testing to ISO 3451-1 and by impact testing to ISO 179/1eA.

Dry-as-moulded parts show lower notched impact than conditioned parts. If assembly involves snap-fits or high-speed impact, post-mould conditioning at 23°C and 50% relative humidity until moisture uptake approaches equilibrium may be required; conditioning time depends on wall thickness and can be estimated by Fickian diffusion calculations. The material is not recommended for continuous load-bearing immersion in hot water, glycol or strong acids. Concentrated formic acid, hydrochloric acid, sulfuric acid and some chlorinated solvents can degrade or stress-crack PA12. In applications involving long-term contact with automotive coolants at temperatures above 100°C, a dedicated chemical resistance test on stressed specimens, such as ISO 22088-2, should be performed.

Tracking resistance and surface electrical behaviour in humid service

Glass-reinforced PA12 exhibits high surface resistivity and a comparative tracking index commonly around 600 V when measured according to IEC 60112 at 23°C. The glass-fibre filler can slightly reduce dry arc resistance compared with unfilled PA12, so components exposed to sustained arcing should be evaluated under the relevant end-product electrical insulation standard. Volume resistivity in the dry state is generally above 10^12 Ω·m under IEC 62631-3-1; after conditioning, the value can fall but remains strongly dependent on moisture content and surface contamination.

Incoming resin should be accepted against the manufacturer’s certificate of analysis for ash content, moisture, colour and melt-flow stability. Glass-fibre-reinforced PA12 is abrasive; screw and check-ring wear can change shot weight over production runs. A shift of more than 1% in shot-to-shot mass at constant temperature settings typically indicates non-return valve leakage or fibre accumulation. Regrind should be dried to the same moisture specification as virgin material and limited to the level validated for the specific part; reclaimed material from sprues and runners containing glass fibre may reduce Charpy impact strength if fibre length is degraded by repeated processing.