EMS-Grivory Grilamid L 25G nat 6011 is a dry-supplied, 25% by weight glass-fibre-reinforced polyamide 12 injection moulding grade. The designation follows ISO 1043 as PA12-GF25; “L” identifies the polyamide 12 backbone, “25G” indicates the nominal glass-fibre content, “nat” indicates natural colour, and “6011” is the supplier-specific release code for the stabilisation and lubricant package. In the dry-as-moulded state, mechanical values are generated under ISO 1110 dry conditions and are not conditioned service values. The grade is specified for technical components requiring low moisture uptake, dimensional stability across humidity changes, low-temperature impact resistance, and resistance to aliphatic hydrocarbons, automotive brake fluids, and zinc chloride solutions.

At 23°C and 50% RH, the equilibrium moisture absorption of PA12-GF25 is approximately 0.10% by weight according to ISO 62, which is substantially below the 1.5% to 2.0% reported for saturated PA66-GF25. The lower amide-group density of the polyamide 12 repeat unit limits the number of available hydrogen-bonding sites for water, preserving a higher fraction of dry-state tensile modulus and reducing moisture-induced linear expansion. This difference is the primary basis for selecting this grade in injection-moulded connectors, clips, and housings in fuel, pneumatic, and hydraulic circuits where component clearances must remain stable across seasonal humidity cycles. Table 1 lists dry-state property values reproduced from published EMS-Grivory datasheet data; they are typical values and are not to be interpreted as guaranteed minima.

Dry-State Conditioning Parameters Define the Processing Window

The material is delivered in moisture-proof packaging with residual moisture below 0.10% by weight. Once the package is opened, pellets should be processed within 24 h when ambient relative humidity exceeds 60%; otherwise pre-drying in a desiccant dryer at 80°C for 4 h to 6 h at a dew point of -30°C or lower is required. Hopper residence time should not exceed 3 h at 80°C because oxidative yellowing may develop in natural colour parts. Melt temperature during injection moulding is typically maintained between 240°C and 270°C, with the nozzle zone set at 260°C and the front barrel zone at 250°C for a 25 mm three-zone screw with L/D of 20:1. Barrel residence time above 270°C should be limited to 10 min; melt temperature above 290°C produces thermal degradation and can reduce notched impact strength by more than 20%.

General-purpose screws without hardened check rings may shorten glass-fibre length and reduce weld-line strength. Screws with nitrided or bimetallic surfaces and compression ratios between 2.0:1 and 2.5:1 are recommended for fibre-length retention. Mould surface temperature should be maintained at 80°C to 100°C for close-tolerance components; below 40°C, high cooling rates suppress crystallinity, increase post-mould shrinkage by approximately 0.1% linear, and can produce a dull, resin-rich surface layer. Mould temperature variation across multi-cavity tools should be controlled within ±5°C because differential crystallisation changes local shrinkage and can produce out-of-round conditions in cylindrical parts. On production-scale injection moulding machines with clamp force from 500 kN to 2000 kN, back pressure is maintained between 2 MPa and 5 MPa to homogenise glass distribution without excessive fibre attrition. Back pressures above 10 MPa are not recommended; published processing data for glass-reinforced polyamides show reductions in average fibre length and notched Charpy impact when specific mechanical energy input exceeds approximately 0.30 kWh/kg.

What Limits Water Absorption and Dimensional Drift in PA12-GF25 Compared with PA66-GF25?

Water absorption in polyamides is controlled by the frequency of amide bonds per unit chain length. Polyamide 12 contains one amide bond per 12 methylene units, whereas polyamide 66 contains one amide bond per 6 methylene units and therefore offers a higher density of hydrogen-bonding amide sites per mass. As a result, PA12-GF25 absorbs less than 0.2% water at saturation by ISO 62, while PA66-GF25 can absorb up to 1.8% by weight. In dry-to-conditioned equilibrium at 23°C/50% RH, PA12-GF25 retains more than 90% of its dry tensile modulus, whereas PA66-GF25 may retain only 75% to 85%. The lower water uptake also reduces linear swelling: a 2 mm thick PA12-GF25 part may show linear dimensional change of less than 0.1% between dry and equilibrium states, compared with 0.3% to 0.5% for PA66-GF25. These values are material-class typical ranges and should be verified for specific part geometry, gate location, and weld-line placement.

In service, the grade is therefore used in compressed-air and fuel-system connectors, cable clips, and automotive fluid-system brackets where moisture-driven clearance changes must remain below assembly tolerance. The glass-fibre content reduces the coefficient of linear thermal expansion to approximately 40 × 10⁻⁶ K⁻¹ in the flow direction and 80 × 10⁻⁶ K⁻¹ transverse to flow, although published data for the exact 6011 variant under all moulding conditions is limited. Anisotropic glass orientation must be considered in circular parts or parts with radial seals. The lower moisture uptake reduces the risk of sealing-surface swell adjacent to O-ring grooves; however, glass-fibre reinforcement roughens the sealing surface and may require polishing or a fibre-free skin layer produced by high injection speed at the end of fill.

For high-volume injection moulding of thin-walled connectors with wall sections below 1.5 mm, filling is improved by increasing injection velocity to 150 mm/s to 300 mm/s and maintaining melt temperature at the upper end of the processing window. High shear rates reduce melt viscosity and improve weld-line strength. Gates should be positioned to orient glass fibres along the primary tensile stress path; gate land lengths of 0.5 mm to 1.0 mm and gate areas not less than 0.5 mm² are typical starting points. Venting is critical because low pellet moisture does not eliminate hot gas generation from additives; vents of 0.015 mm to 0.025 mm depth along the parting line reduce burn marks and short shots. The material is not recommended for hot-runner systems with small nozzle tips below 2.5 mm diameter because glass fibres can accumulate and create flow restrictions. Open nozzles with straight-through bores are preferred over valve gates with narrow annuli.

After moulding, parts may be annealed at 120°C for 2 h in air to improve dimensional stability, but this may alter surface colour and should be validated for natural parts. If the moulded part is exposed to hot air above 120°C for prolonged periods, oxidative embrittlement may occur; continuous-use temperature in air is typically limited to 90°C to 100°C for unreinforced PA12 and may be slightly higher for glass-filled grades depending on load and wall thickness. Contact with aqueous zinc chloride solution at 23°C produces higher stress-cracking resistance than PA66-GF25, which is the reason this grade is selected for automotive cooling and brake-system parts exposed to road salts. Direct contact with strong acids, alkaline oxidising media, or steam above 120°C is not recommended because polyamide hydrolysis degrades molecular mass and impact properties.

Comparative Material Selection Boundaries Across the Grilamid L Family

Within the EMS-Grivory Grilamid L family, increasing the nominal glass-fibre content from 20% to 25% raises dry tensile modulus from approximately 5500 MPa to 6000 MPa and raises the deflection temperature under load at 1.8 MPa from approximately 145°C to 150°C. The 30% glass-fibre grade offers higher modulus, frequently near 7000 MPa, but increases density and melt viscosity, which can reduce flow length in thin sections. The 25G grade is therefore positioned where a balance of stiffness, dimensional stability, and processability is required; it is not the highest-modulus PA12 grade in the family. Compared with unreinforced Grilamid L natural, the 25% glass-fibre content reduces elongation at break from above 50% to below 5%, making the reinforced grade unsuitable for snap-fit deflections that rely on large post-yield strain. For snap-fit designs, lower glass-fibre content or a toughened unreinforced PA12 is preferred.

Against PA66-GF25, Grilamid L 25G nat 6011 shows lower density, typically 1.23 g/cm³ versus 1.30 g/cm³ to 1.35 g/cm³ for PA66-GF25, and lower saturated water absorption. PA66-GF25 has higher heat deflection temperature and higher continuous-use temperature in dry systems, so it is preferred where sustained service above 120°C is required. PA12-GF25 provides better chemical resistance to non-polar hydrocarbons, alcohols, and zinc chloride, and it retains greater impact toughness at sub-zero temperatures due to the flexible PA12 backbone. The dry-state notched Charpy impact of Grilamid L 25G at -30°C is typically retained to within 10% to 20% of the 23°C value, whereas PA66-GF25 may show a larger low-temperature drop. These differences are general to the polymer class and must be confirmed with the supplier’s current datasheet and application-specific testing.

When Drying History and Hopper Residence Time Shift Viscosity and Surface Finish

In multi-shift production, dry-state polyamide 12 can become moist without visible change. When pellets are exposed to uncontrolled plant air at 25°C and 65% RH, the surface moisture content may exceed 0.10% within 4 h, producing splay, drooling, or sporadic gate stringiness. These defects are often misread as melt-temperature problems because the moisture-induced hydrolysis reduces melt viscosity while simultaneously generating volatiles. A halogen moisture analyser calibrated against the supplier method should be used to verify moisture before release to the press; visual pellet inspection is not acceptable. If surface moisture is suspected, the dryer should be run at 80°C with a minimum air flow of 3.5 m³/h per kg/h throughput, and the return-air dew point should remain below -20°C. The same control logic applies to regrind: ground sprue and runner material should be re-dried separately, and regrind fraction should not exceed 25% to 30% unless the process is revalidated, because fibre-length distribution shifts and notched impact strength can decline.

Excessive hopper residence time above 3 h at 80°C can yellow natural parts and consume antioxidant package. In addition, long residence at high temperature shifts the effective melt flow rate upward, which can lead to overpacking and flash. Processors should therefore correlate melt-volume rate by ISO 1133-1 at 275°C/5 kg against retained moisture and hopper residence time before changing shot size or switch-over position. Published data for the specific 6011 variant under humid plant air are limited, so a start-up qualification run at each seasonal humidity boundary is recommended.

Compliance Documentation Required for Technical Component Release

For applications involving continuous pressure containment, published data for the specific 6011 dry variant under cyclic hydraulic fatigue is limited; qualification should follow ISO 9080 or the relevant component-level hydrostatic requirement. The natural-grade product does not contain carbon black and should not be used in outdoor installations without UV stabilisation or painting. If outdoor exposure is required, a black or UV-stabilised variant of the same base polymer should be selected from the supplier’s current product range. Mixing with PA6 or PA66 regrind is not recommended because incompatible melting points, crystallisation kinetics, and amide chemistries can create delamination and variable shrinkage. Residual moisture after storage must be verified by a halogen moisture analyser calibrated against the supplier method before production release.