EMS-Grivory Grilamid L 20 LM Nylon 12, Conditioned is an unreinforced semi-crystalline polyamide 12 injection-moulding grade. The conditioned designation refers to test specimens or finished parts brought to moisture equilibrium under ISO 1110 at 23 °C and 50% relative humidity; it is not a separate copolymer, flame-retardant, or plasticiser-modified product. At this equilibrium the polymer contains approximately 0.7% absorbed water by mass, which is significantly lower than the 2.5% to 2.8% equilibrium moisture uptake of PA66 and PA6 under the same atmosphere. The absorbed water selectively plasticises amorphous regions, lowering tensile modulus and yield stress while increasing fracture resistance measured by notched Charpy impact. Because polyamide 12 has a repeating undecylamide backbone with lower amide-group density than short-chain aliphatic polyamides, the dry-to-conditioned property shift is smaller and the associated dimensional change is reduced. The product therefore occupies a design space between dry unmodified PA12 and moisture-saturated PA66, with applications concentrated in fluid connectors, cable-protection components, electrical housings, and industrial parts requiring low water sensitivity.

How does the conditioned state alter tensile and impact design data?

Moisture uptake disrupts interchain hydrogen bonds in the amorphous phase and lowers the glass transition region; the effect is measurable under standard mechanical test conditions. Under ISO 527-1/-2 tensile loading at 23 °C, unfilled conditioned PA12 of this class exhibits a tensile modulus of approximately 1000 MPa, compared with 1500 MPa for dry-as-moulded specimens. Tensile yield stress falls from roughly 45 MPa to 40 MPa, while elongation at yield rises and notched Charpy impact according to ISO 179/1eA at 23 °C increases from about 4 kJ/m² to 6 kJ/m². The notched impact shift is more pronounced at −30 °C, where dry unfilled PA12 can retain moderate toughness while short-chain polyamides may transition to brittle behaviour. For snap-fit, press-fit, and live-hinge features, conditioned values are the appropriate design baseline because moulded parts reach moisture equilibrium over service life; dry values are valid only for short-term assembly immediately after moulding or in permanently dryrooms.

Lot-to-lot melt volume-flow rate is controlled under ISO 1133-1 at 235 °C with a 2.16 kg load; the L 20 LM designation is positioned for thin-wall injection moulding at moderate flow lengths, while higher-viscosity L 25 grades are preferred for thick-walled pressure-bearing parts. Production tooling should use a general-purpose nylon screw with a compression ratio between 2.0 and 3.0 and an L/D ratio from 18 to 25. The recommended melt-temperature window is 210 °C to 250 °C; the mould surface should be held at 30 °C to 60 °C. Pre-drying at 80 °C in a dehumidifying dryer is required if residual moisture exceeds 0.10%; extended drying above 80 °C or residence times above 10 min at the upper melt-temperature limit can cause chain scission, yellowing, and a measurable loss of melt viscosity. On multicavity hot-runner moulds, the internal lubricant package reduces demoulding force, but venting remains critical because decomposition products from overheated material can deposit on cavity surfaces.

Moulding Parameters That Control Weld-Line Integrity in Thin-Wall Parts

In thin-walled connectors with wall thickness below 1.0 mm, cavity pressure at the end of fill should be maintained between 60 MPa and 80 MPa for unfilled PA12; lower pack pressures increase sink marks and weld-line crack depth. All-electric injection moulding machines with clamp force from 600 kN to 1500 kN are common for 8- to 32-cavity tooling. Short flow paths are preferred because unfilled PA12 has a lower melt stiffness than glass-fibre-reinforced grades. Gate design should avoid pin gates below 0.8 mm for parts thicker than 2.0 mm to prevent shear-induced melt-temperature rise and surface splay. The melt-temperature setpoint is increased to the upper end of the 210 °C–250 °C window only when flow length exceeds 150 mm; this compensates for cooling-related flow-front viscosity increase but shortens the allowable residence time. Weld-line strength measured under ISO 527-2 is often the controlling specification for multi-gated cable clips and circular connector bodies; the conditioned weld-line tensile strength may be approximately 20% lower than the bulk conditioned tensile strength, depending on gate separation and fibre-free polymer flow-front temperature.

Chemical compatibility of conditioned PA12 is most predictable in aliphatic hydrocarbons, automotive fuels, mineral oils, greases, glycol-water coolant, and many industrial solvents of low polarity. Resistance to aqueous salt solutions, including chloride-based de-icing mixtures, is one of the reasons PA12 is used for fuel-vapour connectors and electrical junction housings in vehicle underbody locations. Exposure to concentrated sulphuric acid, nitric acid, phenols, cresols, and hot concentrated formic acid attacks the polyamide chain and is outside the operational boundary of this grade. When contact with a new fluid is evaluated, the test program should follow ISO 175 immersion with conditioned specimens and measure the retention of tensile strength, elongation at break, and mass change. Dimensional stability after moisture conditioning is governed by the low equilibrium uptake of PA12; linear mould shrinkage is in the range 0.8% to 1.2% for unfilled thin-wall parts before annealing, and annealed parts can show lower post-mould distortion in service. These values are lower than typical PA66 shrinkage, but tool design must still account for anisotropic shrinkage in gated areas.

When chloride-salt stress cracking is the controlling failure mode

Automotive underhood and underbody components can see zinc chloride and calcium chloride electrolytes from de-icing road treatments. Chloride-induced stress cracking is a documented failure mode for short-chain aliphatic polyamides under mechanical load, while PA12’s longer methylene sequence and lower amide density reduce the rate of crack propagation. Qualification of PA12 connector bodies intended for fuel-vapour and compressed-air lines often includes stress-cracking protocols that combine a mechanical stress fixture with 5% aqueous zinc chloride at 23 °C and 50 °C. The test outcome is strongly influenced by injection-moulding residual stress; high packing pressure, low mould temperature, and sharp internal radii can reproduce field failure even when the material itself is resistant. Conditioning to 0.7% moisture before chemical exposure increases ductility but may also reduce the critical stress threshold slightly; therefore, the worst-case condition is usually dry-as-moulded parts immediately after assembly. For this reason, annealing at 120 °C to 140 °C in air or oil after moulding is sometimes applied to cable ties and clip bodies before road-salt exposure testing.

After conditioning, electrical properties reflect the low polarity of PA12. Volume resistivity remains in the high-resistance range, but tracking resistance can shift after moisture uptake; decisions for connector insulation should use conditioned specimens rather than dry moulding data. The coefficient of linear thermal expansion of unfilled PA12 is approximately 1.2 × 10⁻⁴ K⁻¹ below the glass transition, requiring snap-fit calculations to include thermal gap closure in engine-compartment locations. When compared with glass-fibre-reinforced PA66, Grilamid L 20 LM shows lower stiffness and lower HDT; it is not a direct replacement in load-bearing structural brackets. Conversely, its lower density of about 1.01 g/cm³ and lower water uptake reduce mass and dimensional change in multi-pin connectors, cable-chain links, and fluid couplings.

How L 20 LM Nylon 12 differs from unmodified L 20, PA6, and PA66

The LM designation in EMS-Grivory nomenclature is associated with an internal mould-release/lubrication modification; the mechanical and thermal specification is otherwise close to the unmodified L 20 series. The principal processing difference is lower demoulding force and reduced mould deposit in continuous operation, which matters in 24/7 production of small connectors. In comparison with conditioned PA66, Grilamid L 20 LM conditioned shows lower tensile modulus and yield stress but more stable dimensions under variable humidity. Conditioned PA66 can absorb approximately 2.5% moisture at 23 °C and 50% RH and may show tensile modulus reductions from dry values in the order of 40%; the corresponding PA12 shift is smaller. In comparison with PA6, PA12 has lower equilibrium moisture uptake and better retention of low-temperature impact, but lower continuous-use temperature under load. The data below summarises representative values rather than specification limits.

Operational boundaries include maximum continuous-use temperature in air of approximately 100 °C to 120 °C for unfilled PA12 depending on load, and short-term peak temperatures not exceeding 150 °C. The grade is not recommended for exposure to concentrated oxidising acids, phenols, cresols, or hot concentrated formic acid. Published data for this specific product under combined cyclic pressure and zinc chloride exposure is limited; qualification programs should use component-level validation rather than relying solely on resin-level chemical immersion data.