Among the low-water-uptake semicrystalline polyamides, EMS-Grivory Grilamid L25 W 10 HX is a medium-viscosity polyamide 12 grade carrying a heat-stabilization package and supplied in a moisture-conditioned state. The base resin is an aliphatic PA12 built from laurolactam or the corresponding 12-carbon aminocarboxylic acid monomer; the longer methylene sequence between amide groups reduces the amide-group concentration relative to PA6 and PA66. This structural difference lowers equilibrium water uptake, reduces dry-to-conditioned stiffness variation, and contributes to the low density observed for the unfilled material: 1.01 g/cm³ under ISO 1183-1. Crystalline melting is recorded between 175 °C and 179 °C by ISO 11357-3, and the glass transition temperature of dry PA12 is commonly reported in the 40 °C to 60 °C range. The medium-viscosity L25 backbone corresponds to a melt volume-flow rate near 10 cm³/10 min at 275 °C under a 5.00 kg piston load with ISO 1133-1.

As-delivered moisture in the conditioned product is not residual contamination; it is a controlled plasticizing burden that raises notched impact response and supports cold forming operations such as tube coiling and flaring. The absorbed water interacts with amide-amide hydrogen bonds in the amorphous regions, reducing tensile modulus while increasing yield elongation. Processors should not interpret a conditioned moisture level of 0.10 wt% to 0.25 wt% as a drying defect. If dry-state stiffness or dimensional freeze is required, the material must be dried actively before processing; if impact-dominated part performance is required, the conditioned state is the more relevant test condition.

Why Does the Moisture-Conditioned Supply State Create a Drying and Feeding Conflict?

The as-delivered moisture burden is intentional, but it must be actively managed when a converter requires dry-as-moulded stiffness or when regrind is processed during humid production months. At ambient relative humidity above 60%, PA12 re-absorbs surface moisture within hours. A dehumidified-air dryer operating at 80 °C to 90 °C with a dew point of −30 °C or lower is recommended; residence times of 4 h to 8 h are sufficient for virgin pellets, while cold regrind may require the longer dwell. Residual moisture below 0.10 wt% is required when reproducing dry-state tensile modulus values. Overdrying or exposure above 100 °C can consume the heat-stabilizer package and shift the material toward the brittle branch; the result is a measurable drop in notched Charpy values and an increase in gate-area cracking on ejection.

On the feed side, conditioned pellets with excessive surface water can bridge in the hopper throat and create screw feed surging. The symptom is a cyclic variation in melt pressure at the injection nozzle or die, typically ±0.5 MPa to ±1.0 MPa on small laboratory injection units. A heated hopper not exceeding 80 °C and a sealed material-transfer line can reduce moisture regain in high-humidity plants. For extrusion lines, a vented screw is generally not required for PA12 if the feed moisture is kept below 0.20 wt%; above that level, microporosity appears in the extrudate as a frosty surface or as flattened voids in tube walls.

Injection moulding barrel profiles from hopper to nozzle are typically set between 220 °C and 250 °C, with mould temperatures held at 40 °C to 80 °C. The mould temperature influences crystallization rate and shrinkage; at 40 °C mould, thin walls crystallize quickly and may show lower shrinkage but higher residual stress, while at 80 °C the material develops a more uniform crystalline morphology and improved dimensional stability, at the cost of slightly longer cooling time. A general-purpose screw with an L/D ratio of 20:1 to 25:1 and a compression ratio near 2.5:1 is standard. High-compression or high-shear screw geometries should not be used without thermal monitoring because shear heating can push melt temperature above 260 °C, initiating thermo-oxidative chain scission and causing yellowing or a change in melt viscosity.

On production-scale cold-runner injection machines with clamp capacities from 50 t to 250 t, short shot and flash often coexist when the melt temperature is too high and the hold pressure is insufficient, because the low melt viscosity of conditioned PA12 at 240 °C can overfill thin edges while the gate freezes prematurely if the nozzle or hot-runner manifold is underheated. Monitoring nozzle pressure transducers and setting a short hold-pressure profile with a fixed decay step reduces this.

For tubing and profile extrusion, the conditioned state improves flexural ductility during coiling and reduces die lip build-up compared with a fully dried pellet. Single-screw extruders are normally run with cylinder temperatures of 200 °C to 230 °C and a die temperature of 220 °C to 240 °C. A downstream vacuum calibration trough with a first cooling zone at 20 °C to 40 °C is used to set outer diameter and wall thickness. Operators should monitor die swell because PA12 exhibits a moderate level of shear-dependent elastic recovery; die swell is typically controlled empirically by adjusting draw ratio and cooling-water vacuum rather than by changing melt temperature alone. Published data for die swell of this specific W 10 HX conditioned variant is limited, so tooling dimensions should be qualified on a pilot line before cutting full production dies.

Moisture- and Temperature-Dependent Mechanical Data for Dry and Standard-Conditioned Specimens

The following table consolidates representative values from public PA12 L25-family technical literature. Unless otherwise noted, specimens are prepared according to ISO 294-1 and tested under ISO 527-1/-2, ISO 179-1/1eA, ISO 75-2, and ISO 62. Conditioned values refer to equilibrium at 23 °C and 50% relative humidity. These values are typical ranges and should not be treated as specification minima or maxima; batch-release certificates for the W 10 HX grade take precedence.

The mechanical shift from dry to conditioned is not a linear function of moisture content. The first 0.10 wt% of absorbed water produces the largest reduction in tensile modulus because water molecules disrupt interchain amide-amide hydrogen bonds in the amorphous regions; beyond 0.20 wt%, further softening is smaller, while the notched impact response continues to improve until equilibrium. Processors who dry the material to recover stiffness should therefore expect a large change in short-term tensile properties but a smaller change in low-temperature impact if the parts are later conditioned in service.

Where This Grade Diverges From PA6, PA66, and Unconditioned PA12 Systems

PA12 differs from PA6 and PA66 principally in amide-group concentration. Saturated water uptake of unreinforced PA6 is commonly reported near 9 wt% and PA66 near 8 wt% under ISO 62; the PA12 range near 1.5 wt% results in a smaller dry-to-conditioned stiffness swing and better retention of dimensions in humid service. For the same water uptake, PA12 has a lower melting point of 176 °C to 179 °C than PA66 at 260 °C to 265 °C, and thus requires lower melt processing temperatures and less energy in the hot-runner and barrel zones. The cost is a lower deflection temperature under load: unreinforced PA12 typically exhibits a heat deflection temperature under 1.8 MPa near 50 °C, whereas PA66 may exceed 70 °C under the same method.

Within the PA12 family, the heat-stabilized and conditioned Grilamid L25 W 10 HX grade is positioned for processing routes that use the delivered moisture to improve impact behaviour. Compared with a fully dried, non-heat-stabilized PA12, the conditioned product shows a higher notched impact response and a lower tensile modulus on arrival. The heat-stabilization package is intended to slow thermo-oxidative degradation during exposure to elevated air temperatures; however, it does not confer unlimited hot-water or steam resistance. Continuous service in hot water or steam above 80 °C should be qualified for the specific part and wall thickness because hydrolysis of the amide linkage remains the long-term failure mechanism for all aliphatic polyamides.

When a Metal Tube or a Rigid Engineering Thermoplastic Is Replaced in Air and Fuel-Vapour Systems

In compressed-air lines and low-pressure fuel-vapour conduits, the grade is selected for vibration tolerance, corrosion resistance, and lower part count when formed into one-piece assemblies. The conditioned PA12 material can be coiled, flared, and secured with barbed fittings; the moisture-induced ductility reduces the risk of splitting during insertion. However, the material does not replace metal tube where sustained burst pressure or elevated temperature dominates. Published data for long-term pressure regression of this specific W 10 HX conditioned variant is limited, so the system should be validated under service temperature and pressure cycling, not extrapolated from short-term tensile data.

For cable sheathing and snap-fit connectors, the material competes with plasticized PA12 and thermoplastic elastomers. It provides superior chemical resistance to aliphatic oils compared with many TPE grades and lower water absorption than PA6. However, unfilled PA12 shows moderate abrasion resistance; sliding contact under load may require a higher-hardness PA12 grade, a glass-filled PA12, or an alternative polymer. The material is also incompatible with strong mineral acids, concentrated formic acid, and strong oxidizing agents; contact with such media at elevated temperature can cause stress cracking or rapid molecular weight loss.

When transitioning from PA66 to PA12 in injection moulding or extrusion, the machine should be purged with a low-viscosity polyolefin or a commercial PA purge compound because residual PA66 in the hot runner can degrade at PA12 processing temperatures and produce black specks. Reverse transition from PA12 to PA66 requires thorough purging because PA12 retained in the barrel can degrade at PA66 melt temperatures above 260 °C. Final component qualification therefore requires pressure cycling, temperature ageing, and fitting retention testing on the actual production wall thickness; material data alone do not establish service life.