EMS-Grivory Grilamid® L 20 nat is supplied as a natural-coloured, medium-viscosity polyamide 12 resin with pellet geometry suitable for both extrusion and injection molding. The grade is designated PA12 under ISO 1043; the natural formulation contains no carbon black, making it usable for in-house pigmentation or translucent articles where visual inspection of internal flow channels is required. Representative producer data list a melt volume rate of 8 cm³/10 min when measured at 275 °C under a 5 kg load according to ISO 1133-1. The dry molding compound density is 1.01 g/cm³ according to ISO 1183-1. Water uptake at saturation in 23 °C distilled water is approximately 1.5% by mass under ISO 62, while equilibrium atmospheric moisture uptake at 23 °C and 50% relative humidity is in the range of 0.6–0.7%. The semicrystalline structure produces a melting peak of 178 °C by differential scanning calorimetry under ISO 11357-1/-3 and a Vicat softening temperature of 140 °C under ISO 306 using the B50 method. The heat deflection temperature under 1.8 MPa loading is approximately 50 °C, while the 0.45 MPa value is 115 °C per ISO 75-2.

Comparative class data show unfilled PA6 and PA66 dry tensile moduli in the ranges of 2800–3300 MPa and 2800–3200 MPa, respectively, placing Grilamid L 20 nat in a lower-stiffness, higher-elongation position. Its density is approximately 0.11–0.13 g/cm³ below PA66 and 0.11–0.12 g/cm³ below PA6. Saturation water uptake of PA12 in 23 °C water is approximately 1.5% by mass, against class values of 9.5–10.0% for PA6 and 8.0–9.0% for PA66 under ISO 62. This reduces the modulus swing between dry and conditioned states and supports thin-walled parts that must retain dimensional stability across seasonal humidity changes. The longer aliphatic segment lowers the melting point relative to PA66; where a PA66 grade typically melts between 255 °C and 265 °C, Grilamid L 20 nat melts at 178 °C and is not specified for continuous service above 120 °C unless application-specific aging data support such use.

Fine-Gauge Extrusion Parameters and Melt Stability in Conduit Production

Tubing lines converting Grilamid L 20 nat into 4–12 mm outside-diameter pneumatic or fuel-sensor conduits typically employ a single-screw extruder with a 24:1 to 30:1 L/D ratio, a three-zone screw with a compression ratio of 2.5:1 to 3.0:1, and a breaker-plate screen pack of 80/120/80 mesh. Cylinder zone temperatures are set from 230 °C in the feed throat to 260 °C at the metering zone, while die-head temperatures are held between 250 °C and 270 °C. The melt-pressure signal before the die should remain below 300 bar; a rapid rise above that value usually indicates a blinded screen pack or insufficient melt temperature in the adapter. For a 1.0 mm wall tube, haul-off speeds of 20–60 m/min are used with a water-bath temperature of 20–40 °C. Dimensional control is verified under ISO 23529 or an internal optical comparator; online ultrasonic wall-thickness monitoring is recommended when the wall falls below 1.0 mm because the ratio of die gap to drawn wall influences both ovality and burst-pressure retention.

Where the resin is used as a 0.4–1.2 mm protective jacket over optical-fiber buffer tubes in outdoor drop cable, the selection of Grilamid L 20 nat over PA6 or PA66 follows from the lower saturation water uptake and the retention of a lower modulus after conditioning. A jacket produced at 1.0 mm wall thickness can be evaluated for shrinkage under IEC 60794-1-2 method F5 or an 80 °C air-oven exposure; the semicrystalline growth in PA12 typically produces post-extrusion jacket shrinkage below 0.5% when the line is operated with a controlled annealing zone at 60 °C before final cooling. The measurement is made on the finished cable because the fiber buffer and strength elements constrain the jacket; isolated plaque shrinkage under ISO 294-4 does not transfer directly to the cable construction. Aramid yarn counts and water-blocking yarn tension must be fixed before lot comparison, because both alter the residual compressive load on the jacket.

How Does L 20 nat Generate a Different Notched Impact Signature Than Short-Chain Aliphatic Polyamides?

The long aliphatic segment between amide linkages in PA12 lowers the density of hydrogen bonding per unit chain mass relative to PA6 or PA66. In a dry 23 °C Charpy test conducted under ISO 179/1eA, the notched impact behavior of Grilamid L 20 nat remains ductile at thicknesses where a dry PA6 molding of comparable molecular weight may drop below 5 kJ/m². The difference is not explained by the dry tensile modulus, which is lower than the PA6 class range of 2800–3200 MPa and therefore reduces notch-tip stress concentration. The fracture surface in a scanning electron microscope examination of a dry impact failure typically shows stress-whitened craze remnants rather than the clean cleavage steps observed in semicrystalline short-chain nylons at 23 °C. Published data for this specific morphological interpretation are limited when the specimen is conditioned to 50% relative humidity; the producer datasheet does not supply a fracture-mechanics KIc value.

When the material is injected into an 8-cavity hot-runner tool with a 200-metric-ton clamp force, shear heating in the manifold may raise the melt stream to 300 °C even though the barrel setpoint remains at 260 °C. In such a configuration, externally heated hot-runner drops with an internal melt channel of 8–10 mm diameter are preferred over internally heated bushings, which produce local stagnation. The hold-pressure phase should be set at 600–800 bar hydraulic pressure and held for 3–5 s for a 2.5 mm wall thickness. A mold temperature of 60 °C is the recommended upper bound for dimensional stability; temperatures above 80 °C retard formation of the spherulitic skin and extend cycle time without a corresponding gain in stiffness. Gate blush in natural PA12 is controlled by injection velocity profiling, with the initial screw velocity capped at 30–40 mm/s for the first 1.5 s. The resulting parts are visually inspected under a 20× stereo microscope for voids at the gate interface.

Low-frequency electrical connector bodies molded from the natural grade are often conditioned for 48 h at 23 °C and 50% relative humidity before flash-over testing. Volume resistivity under IEC 62631-3-1 is in the region of 1×10¹² Ω·m, and surface resistivity under IEC 62631-3-2 is in the region of 1×10¹³ Ω; these values depend strongly on antistatic additive selection. If an antistatic or conductive carbon black masterbatch is added, the base resin electrical insulation profile is no longer representative, and each batch must be tested on the finished geometry according to the relevant product standard.

When Pre-Drying and Residence-Time Control Determine Molded Part Consistency

Drying before processing is a boundary condition rather than an optional preparation. At ambient relative humidity above 60%, pellets can reach a surface moisture level sufficient to hydrolyze amide linkages during plastication; the producer recommends 80 °C for 4–6 h in a desiccant dryer with a dew point of -30 °C or lower. A residual moisture target below 0.10% by weight is appropriate for injection molding. Melt residence time above 10 min at 280 °C in a 25:1 L/D barrel increases yellowing and reduces notched impact strength; in a 40 s cycle, a shot weight below 30% of the barrel capacity is not recommended because prolonged residence time in the compression zone shifts the molecular weight distribution downward. Additive combinations should be qualified by melt-flow monitoring under ISO 1133-1 before production, because PA12 degradation pathways are sensitive to the ligand chemistry of the stabilizer package. If regrind is used at 20–30 wt%, it should be dried to the same moisture specification and blended with virgin pellets in a continuous gravimetric batch blender.

Fuel-line validation requires separate chemical resistance characterization because fuel permeation and aging do not follow the short-term tensile property profile. Tubing produced from PA12 is typically aged in test fuels and subjected to burst-pressure retention according to the original equipment manufacturer specification; DIN 73378 is used as a base evaluation for polyamide tubing in motor vehicles. In such tests, the dimensional change and tensile strength retention depend on the aromatic content of the fuel and on the surface-to-volume ratio of the wall. Published data for this specific configuration is limited because fuel formulations vary by region and season.

Thin-walled clips and connectors for non-implantable pharmaceutical handling equipment are evaluated under ISO 10993-1 only as finished devices; the natural PA12 base resin provides a non-pigmented starting point for low-extractable systems. Extraction behavior is not governed solely by the base polymer but by mold release, processing temperatures, and post-molding annealing. A solvent rinse in isopropyl alcohol at 60 °C for 10 min can reduce surface oligomers but must be validated for each geometry.

Gas-assisted molding of corrugated automotive ducts in Grilamid L 20 nat imposes a different constraint: the nitrogen injection pressure must overcome the melt yield stress at the core without exceeding mold clamping force capacity. For a duct with a 40 mm outer diameter and 2.5 mm wall, tool pressure sensors frequently record 80–120 bar during gas packing; the resin remains sufficiently fluid at 260 °C to transmit gas pressure along the core, while the outer skin solidifies against the 60 °C mold face. The natural color allows visual confirmation of void continuity in sectioned trials; black or pigmented grades would obscure the gas-channel position. Dimensional recovery after 1 h at 120 °C according to ISO 2505 is used as a production control for relaxation in the curved sections.