EMS-Grivory Grilamid® L 25 Z is an unreinforced impact-modified polyamide 12 injection-moulding grade identified under ISO 1874-1 as PA12-I. The product is supplied as cylindrical granules and is specified for high-flow injection moulding of thin-wall technical components. Manufacturer-published property values include an ISO 1183-1 density of 1.01 g/cm³, an ISO 11357-1/-2 melting peak of 178°C, and an ISO 62 moisture uptake of 0.7% at 23°C/50% RH. The melt volume-flow rate is determined under ISO 1133-1 at 275°C/5.0 kg; product-specific values in the current EMS technical datasheet should be used for gate sizing, because impact-modified PA12-I grades in this viscosity class typically span 15–30 cm³/10 min. The combination of a PA12 backbone with impact modification shifts the ductile-brittle transition below 0°C while maintaining a moisture absorption roughly one-third that of PA6 and PA66. The grade is therefore used in connectors, clips, pneumatic couplings, cable ties, and housings in which dimensional stability under humid air and resistance to aliphatic hydrocarbons are required simultaneously. It is not a structural high-modulus material; ISO 527-1/-2 tensile modulus remains below 2000 MPa, and continuous load-bearing functions should be transferred to reinforced PA12 grades unless creep testing under defined load and temperature has been completed.

What Distinguishes Grilamid® L 25 Z from Unmodified PA12 Grades?

Impact modification alters the mechanical failure envelope while leaving the base PA12 chemical resistance largely intact. Under ISO 179-1/1eA notched Charpy testing, the impact-modified grade retains a meaningful fraction of its ambient impact energy at −30°C, whereas unmodified low-viscosity PA12 grades typically fall below 5 kJ/m² in the same specimen geometry. The low-temperature response is obtained at the cost of a 10–15% reduction in tensile modulus relative to unmodified high-flow PA12; published ISO 527-1/-2 values for the impact-modified composition lie in the 1300–1600 MPa range. Under ISO 899-1 tensile creep, sustained stress at 80°C should be restricted to 6–8 MPa if cumulative strain is to remain below 1.5% over the service interval. The unreinforced impact-modified grade also differs from glass-fibre-reinforced PA12 products in its more isotropic moulding shrinkage. ISO 294-4 measurements are typically 1.0–1.5% in the flow direction and 1.2–1.6% transverse, reducing warpage in multi-gate thin-wall geometries at the expense of tensile stiffness. Weld-line strength in the impact-modified grade is less sensitive to moisture conditioning than in PA6, but it remains 20–30% below the bulk strength when mould temperature falls below 40°C.

Comparative published values for unreinforced polyamide grades are shown in the table; values are typical dry-as-moulded or conditioned figures and must be verified against current datasheets for a specific lot.

Across production lines using 40 mm three-zone reciprocating screws with L/D 20, 50–80 bar back pressure, and 20–30 mm/s injection speed on thin-wall tooling, the material reaches homogeneous melt clarity only when pellet moisture is below 0.10%. Opened containers on a floor at relative humidity above 60% absorb surface moisture within 24 h; the first indicators are splay and a 5–10 bar drop in melt-pressure stability during dosing. The documented failure mode is not purely visual. Moisture attacks the impact modifier at the weld line, and notched Charpy values can fall by 20–30% before surface splay becomes prominent. On one production run, mould-temperature variation of ±10°C across an eight-cavity tool produced 0.2% spread in outer diameter between cavities, causing assembly rejection in a snap-fit connector. The corrective action on manufacturing lines is desiccant drying at 80°C for 4–6 h with a dryer dew point of −30°C or lower. For central conveying systems, return-air sensing should be used because PA12 pellets can bridge in hoppers and leave core resin at unacceptable moisture.

Melt Processing Boundaries and Drying Requirements

Injection moulding of EMS-Grivory Grilamid® L 25 Z requires a melt-temperature window of 220–250°C, with short excursions to 260°C permitted for thin-wall fill if residence time is kept below 5 min. Mould temperature is set between 40°C and 80°C; the lower boundary is governed by premature freezing in sections thinner than 1.0 mm, while the upper boundary controls cycle time and crystallinity-dependent shrinkage. On hot-runner systems, gate temperature should be 250–260°C and the manifold should not exceed 270°C; thermal degradation of the impact modifier produces acidic odour and black specks. Screw design on 25–40 mm injection units should use L/D 18–22 and compression ratio 2.0–2.5. Venting depth between 0.01 mm and 0.02 mm is required at the end of fill to prevent burn marks and mould deposits from low-molecular-weight fractions. Gate size should not be reduced below 0.8 mm for tab gates; tunnel gates below 0.6 mm generate excessive shear heating and visible jetting in unreinforced PA12-I. Where colour masterbatch is metered at the feed throat, let-down ratios of 2–3% are typical, and a mixing nozzle with 6–10 mm spiral insert is used. For re-compounding of regrind, a 27 mm co-rotating twin-screw extruder with L/D 32 and vacuum venting at −0.9 bar is adequate; barrel profile is 210–240°C and die pressure is maintained below 70 bar. Regrind content above 30% lowers Charpy notched impact by 10–20% and is not recommended for cold-weather pneumatic couplings.

In non-isothermal differential scanning calorimetry at 20 K/min, the grade shows a crystallisation peak between 150°C and 160°C; this narrow supercooling window requires that mould temperature be held near the upper end of the recommended range for consistent semicrystalline skin formation. Slow cooling below 20 K/min increases crystallinity and raises density by 0.2–0.5%, which must be considered when quoting dimensional inspection results after annealing at 120°C for 2 h. Because the grade contains no glass-fibre reinforcement, barrel and screw wear is lower than with reinforced PA12; however, the impact-modified melt has higher pvT compressibility and can trap gas in thick sections if decompression before retraction exceeds 3 mm.

Chemical exposure data for PA12-I are derived from immersion testing according to ISO 1817 and internal automotive fluid conditioning. The grade withstands continuous contact with diesel, mineral oil, grease, aliphatic hydrocarbons, and zinc chloride solutions at temperatures up to 60°C with limited mass change; published swelling in ASTM D471 reference fuel C is typically below 3% after 72 h at 23°C. Exposure to strong mineral acids, phenolic compounds, and concentrated formic acid leads to surface etching or stress-cracking when moulded-in stress exceeds 10 MPa. Alcohol-based fuels and high-aromatic refinery streams produce higher swell than pure aliphatics; components for aggressive oxygenated fuels should be validated by component-level testing under 60°C continuous immersion. In low-temperature pneumatic service, the combination of impact modification and low water uptake preserves snap-fit retention forces better than PA66 after 1000 h at 85°C/85% RH; ISO 1110 accelerated conditioning shows PA66 gains 2.0–2.5% moisture while PA12-I remains below 1.0%. The product is not recommended for continuous immersion in hot water above 80°C because hydrolytic chain scission accelerates; published data for this specific configuration in chlorinated water above 60°C is limited.

When Polyamide 12-I Replaces Polyamide 66 in Dimensional Stability-Limited Applications

Substitution of PA66 with the PA12-I grade is justified only when the component design is limited by moisture gain rather than by absolute strength or peak temperature. A housing moulded from PA66 absorbs sufficient water under 50% RH to reduce tensile modulus by 20–30%; the PA12 grade loses less than 10% over the same conditioning interval because its equilibrium moisture is below 0.7%. The trade-off is thermal: ISO 75-1/-2 heat deflection temperature at 1.8 MPa is approximately 50°C for PA12-I, compared with 75°C for unreinforced PA66. Applications requiring continuous load above 1.8 MPa at 90°C should remain in PA66 or move to a reinforced semi-aromatic polyamide. Dimensional change data from ISO 294-4 show lower absolute shrinkage in PA12-I than in PA66; this simplifies tool compensation across humidity exposure but increases sensitivity to mould-temperature variation. Processors report that mould-temperature variation of ±10°C shifts PA12-I shrinkage by 0.15–0.25%, which is larger than for PA66 because of the lower crystallisation temperature. Tooling should therefore use conformal cooling and cavity-pressure sensing to maintain ±5°C uniformity on close-tolerance parts. In dimensionally stable connectors exposed to humid air, PA12-I provides a closer match to steel inserts than PA66 because its linear coefficient of thermal expansion under ISO 11359-1/-2 is 100–120 × 10⁻⁶/K and its moisture expansion is lower.

For electrical and electronic housings, the unreinforced grade exhibits volume resistivity above 10¹³ Ω·m under IEC 62631-3-2 and dielectric strength above 30 kV/mm under IEC 60243-1 on 3.0 mm plaques. These values do not substitute for creepage and clearance verification under the end-product standard. Coefficient of linear thermal expansion under ISO 11359-1/-2 should be entered into finite-element solvers as a temperature-dependent curve rather than a single linear coefficient because the PA12-I expansion rate increases near the glass transition. For snap-fit geometries, the secant modulus at 2% strain rather than the initial tensile modulus should be used in beam equations because the stress-strain curve departs from linearity early. Mould-filling simulation requires a pressure-dependent viscosity model calibrated by capillary rheometry under ISO 11443 at three temperatures and shear rates from 100 s⁻¹ to 10⁴ s⁻¹.

In railway interior parts, the natural unreinforced grade should not be specified for EN 45545-2 fire-hazard requirements without flame-retardant validation, because unreinforced PA12-I typically reaches only HB under UL 94 at 3.0 mm. For exterior underbody clips exposed to salt spray and stone impingement, the material retains impact resistance better than glass-filled PA66 at −40°C, but colour stability under UV requires carbon black or UV-stabilised grades.

Regulatory conformance statements for the natural grade are limited to the base polymer and do not automatically cover pigmented or laser-marked variants. The compliance matrix below should be confirmed with lot-level documentation when migration or electrical testing is part of the approval package.

The grade is differentiated from polyamide 11 by a lower melting point of 178°C versus 189°C for PA11 and by slightly lower moisture uptake, while retaining similar aliphatic-fuel resistance. Compared with polyether block amide elastomers, Grilamid® L 25 Z is stiffer and better suited to snap-fit connectors, but it has substantially lower dynamic flexural fatigue above 3% cyclic strain. Published data for this specific configuration under high-frequency cyclic loading is limited; component-level flexural fatigue testing is required before replacing PEBA in dynamic bellows or tubing.