EMS-Grivory Grilamid L 20 LF grey is an unreinforced, internally lubricated polyamide 12 injection moulding grade supplied in a moisture-conditioned state. The designation places the material within the PA12 family according to ISO 16396-1, and the LF suffix indicates a low-friction additive package distributed through the polymer matrix. The grey colour is part of the base compound, not a surface finish. The conditioned state refers to equilibrium moisture uptake at 23 °C and 50 % RH in accordance with ISO 291:2008; it is not saturated water absorption and not a superficial surface film. The unreinforced density is approximately 1.01 g/cm³ under ISO 1183-1, and the typical melt temperature window for injection moulding is 220 °C to 250 °C. The product should be handled as a hygroscopic technical polymer rather than as a commodity polyolefin, because moisture content changes both processing viscosity and final part dimensions.

At the molecular level, polyamide 12 has a lower amide group density than PA6 or PA66. That structural feature reduces the equilibrium moisture uptake and contributes to dimensional stability and low-temperature ductility. The crystallite melting point is approximately 178 °C under ISO 11357-3. The synthetic route from laurolactam or ω-aminolauric acid is documented in polymer science literature, but the stabilizer and lubricant masterbatch composition in the LF grade is manufacturer-confidential. The melt is a viscoelastic fluid with viscosity controlled by the selected PA12 relative viscosity. The grade designation L 20 normally identifies the viscosity level; the LF suffix is the low-friction modification, not a reinforcement or impact-modifier classification.

How Does Moisture Conditioning Alter the Tensile Response?

The uptake of water in the amorphous phase lowers the tensile modulus and yield stress while increasing elongation and impact toughness. Under ISO 527-1/-2 tensile testing at 23 °C, conditioned specimens of this grade show a tensile modulus below 1200 MPa, while dry-as-moulded values are typically above 1400 MPa. The yield stress shift is proportionally smaller; published datasheet values for similar unreinforced PA12 low-friction grades place conditioned yield stress between 38 MPa and 45 MPa. Elongation at yield is typically above 10 % after conditioning, and elongation at break often exceeds 50 % when measured at 50 mm/min. Because modulus is strain-rate-dependent and moisture-dependent, a measured value without a stated conditioning state is not technically comparable.

Notched Charpy impact energy under ISO 179-1/1eA increases significantly after conditioning. For unreinforced PA12, a dry notched impact value near 5 kJ/m² can rise to 10–15 kJ/m² after conditioning at 23 °C and 50 % RH. The exact figure depends on notch radius, moulded skin orientation, and the cooling rate used in the mould. In dynamic mechanical analysis, the glass transition of dry PA12 is commonly observed between 40 °C and 50 °C; absorbed water broadens and lowers this transition, which explains the more reliable ductile failure mode of conditioned parts at room temperature. The moisture effect is reversible in principle, but repeated drying and reconditioning cycles can alter crystallinity and should not be used as a design simulation.

Moisture uptake follows a diffusion-controlled process. For thin sections, equilibrium at 50 % RH may require days to weeks depending on wall thickness and ambient airflow. A 2 mm thick plaque reaches equilibrium more quickly than a 4 mm wall section, which means the laboratory-conditioned tensile bar may not represent the core of a thick production part. This thickness dependence is important when using conditioned datasheet values for large structural components.

Conditioning also changes part dimensions and assembly behaviour. Unreinforced PA12 grades typically show mould shrinkage in the range of 0.7–1.2 % parallel to flow and 0.8–1.3 % transverse when measured on 60 mm × 60 mm × 2 mm plaques according to ISO 294-4. After exposure to the conditioned atmosphere, the equilibrium volume increase is roughly 0.5–0.7 %. Snap-fit interference, bearing clearances, and heat-staked joints should therefore be calculated using conditioned dimensions. In production, mould temperature and holding pressure have a stronger effect on shrinkage than the lot-to-lot variation in melt viscosity, so consistent cushion control and switch-over position are more effective than adjusting melt temperature alone.

Low-Friction Additive Chemistry Without PTFE

The LF version contains an internal lubricant system that lowers the coefficient of friction in unlubricated service. Unlike an external coating, the additive is distributed in the melt and remains present after machining or surface wear. The formulation is not a PTFE compound; it is designed to reduce stick-slip without the deposit issues sometimes associated with external silicone or PTFE films. The coefficient of friction is not an intrinsic material constant. It depends on counterface hardness, roughness, sliding velocity, contact pressure, and interfacial temperature. Validation should therefore use the intended counterpart material and a defined tribometer such as a pin-on-disc apparatus operated under ASTM G99 or a polymer-bearing test under ISO 7148-2. Published data for this specific grey LF grade is limited, and comparative wear or friction claims should be verified on production-representative surfaces.

Because the base polymer is unreinforced, the load-bearing limit is below that of glass-fibre reinforced PA12. Friction reduction at low loads does not imply suitability for high-pressure sliding. If the application involves surface pressures above 10 MPa, a reinforced tribological grade with solid lubricants may be required. That substitution must be evaluated against the full mechanical load case, including creep under ISO 899-1 and notched impact under ISO 179-1/1eA.

The practical difference between this PA12 grade and an unreinforced PA66 grade appears most clearly in humid or cold environments. Because the PA12 matrix reaches equilibrium moisture at roughly one-quarter to one-third of the PA66 level, the mechanical property shift between dry and conditioned is smaller, and electrical insulation values are more stable. The lower density also reduces part mass in multi-cavity automotive connectors. However, the lower melting point of PA12 means that the upper service temperature is more restricted than PA66. Continuous use in air at temperatures above 100 °C requires long-term thermal-oxidative stabilizer evaluation. That evaluation is normally carried out by accelerated oven aging according to ISO 2578 or property retention after heat aging under customer-specific protocols. The same temperature restriction applies to under-hood locations with sustained heat soak.

Electrical connectors and low-voltage insulation components also select PA12 because the dielectric properties remain more stable in humid air than those of PA66. The grey pigment does not automatically provide UV stabilization, so outdoor exposure above extended solar load requires UV-stabilized variants or black or custom colours, unless weathering testing under ISO 4892-2 demonstrates sufficient retention. The low-friction additive may influence surface deposition behaviour in electrical contacts, so contact resistance testing should be performed on actual finished parts.

When the Part Is Exposed to Zinc Chloride Road Salts

Cold-climate under-hood and exterior fasteners may contact road de-icing salts containing zinc chloride. PA12 generally offers better resistance to zinc chloride stress cracking than PA6 and PA66, but the resistance is not absolute and is strongly temperature-dependent. For qualification, moulded test specimens should be exposed under controlled strain using ISO 22088-2 or ISO 22088-3 with the actual salt concentration and preload. A generic chemical resistance table is not sufficient for safety-relevant parts. The LF additive package does not contribute to environmental stress-cracking resistance; it only modifies the surface friction and wear response. If the application combines mechanical preload, zinc chloride, and cyclic thermal expansion, the failure mode can shift from ductile yielding to slow crack growth. In such conditions, prototype testing should include temperature cycling from -40 °C to 80 °C rather than isothermal immersion only.

Drying Prior to Moulding Prevents Hydrolytic Viscosity Loss

The incoming moisture-conditioned state is relevant for end-use properties but not always for processing. If sealed packaging has been opened for several hours in humid air, the granulate surface may contain excess moisture. A desiccant dryer with a dew point of -30 °C or lower and an air temperature of 80 °C is recommended for 4–8 h when the moisture content exceeds 0.1 %. Vacuum drying at 80 °C can shorten the drying interval, but the dryer must maintain a closed-loop air supply. During melting, water can hydrolyze the polyamide chain, lowering melt viscosity and causing splay marks on the moulded surface. The melt should be kept below 250 °C, and residence time should be minimized. On a reciprocating screw with 20:1 L/D and a compression ratio of 2.0–2.5:1, the plasticating unit should be operated with a moderate recovery speed to avoid excessive shear heating. The screw geometry should provide gradual compression and a mixing section that does not create stagnant melt.

At typical processing shear rates from 100 s⁻¹ to 1000 s⁻¹, the apparent melt viscosity of unreinforced PA12 at 240 °C is normally in the range of 100 Pa·s to 300 Pa·s. The LF additive may lower viscosity slightly, but the base resin relative viscosity exerts the dominant control. Mould-filling simulation should use capillary or slit rheometry data from the specific lot rather than a single melt flow index, because polyamide rheology is shear-thinning. Melt pressure at the machine nozzle can range from 60 MPa to 120 MPa depending on part geometry and gate size.

For thin-wall parts below 1.5 mm, the conditioned low-friction grade can be moulded with moderate injection pressure, but high injection velocity is often needed to reach the end of flow before the melt skin solidifies. Because unreinforced PA12 has a relatively sharp melt-to-crystal transition, tool surface temperature influences the skin-core morphology and post-moulding shrinkage. Mould temperatures of 40 °C to 80 °C are common; the higher end promotes crystallinity and surface gloss but increases cycle time. In multi-cavity tools, the filling imbalance across the runner system should be kept below 5 % by mass to avoid differential shrinkage and dimensional mismatch. Hot-runner manifolds should be designed with closed-loop tip temperature control and no flow dead spots, because stagnant melt in hot runners can undergo discoloration in the grey compound and release degradation products into the flow stream.

The low-friction performance is most reproducible when the moulded surface is allowed to develop its natural skin layer. Mould release sprays or external lubricating films can interfere with the internal lubricant mechanism and should be avoided unless specified for the application. For moving parts such as cable ties, snap-fit clips, and sliding guides, the conditioned ductility permits assembly at low ambient temperatures down to -40 °C, but the specific impact performance at that temperature should be confirmed by lot-specific testing under ISO 179-1/1eA.

The grade is not a direct replacement for glass-fibre reinforced PA12 in structural housings or brackets where tensile modulus above 3000 MPa is required. Unreinforced PA12 tensile modulus is below 2000 MPa even in dry conditions, and conditioning lowers it further. Load-bearing calculations should use the conditioned modulus at the maximum service temperature. The product is also not intended for continuous immersion in strong acids, oxidizing media, or hot water above 80 °C without specific validation; PA12 can undergo hydrolysis in aqueous service at elevated temperature. Published data for this specific grey LF grade is limited in such media, and part tests must be performed on moulded components rather than on raw granulate.