EMS-Grivory Grilamid LV-3 ESD is a polyamide 12 (PA12) injection-molding resin reinforced with 30 % glass fiber by weight and modified with an electrically dissipative additive system. The grade is supplied as black granules and is typically processed by conventional screw injection molding. The “conditioned” designation refers to the moisture-equilibrated state at 23 °C and 50 % RH in accordance with ISO 291; this state is technically significant because absorbed water reduces the matrix-dominated stiffness response of the PA12 while the glass-fiber phase remains essentially unaffected. Unlike a non-ESD structural grade, the dissipative additive network survives normal melt processing and is distributed through the polymer matrix, so the electrostatic discharge control function is not a removable surface layer.

The distinction between the non-ESD Grilamid LV-3 H and the ESD variant is controlled by the conductive additive package, not by glass content. Both grades use a 30 % glass-fiber reinforcement by weight. The ESD modification reduces some matrix-dominated ductility indicators but brings surface resistivity into the static-dissipative range. The degree of shift can only be assessed on conditioned specimens because the ESD additive and moisture interact at the specimen surface.

How Does Moisture Conditioning Alter the Design Allowables for a 30 % Glass-Fiber PA12?

Conditioning at 23 °C / 50 % RH typically produces a moisture uptake of approximately 0.5 % by weight for this composition. The effect on design allowables is nonuniform: tensile modulus and flexural modulus decline by roughly 25 % to 35 %, while notched impact strength rises because the amorphous polyamide phase becomes less brittle. The table below lists representative injection-molded data; these are typical values, not guaranteed specification limits, and should be qualified by lot-specific certificates of analysis.

For structural design, the dry and conditioned values should be treated as two separate constitutive states. When a snap-fit beam is analyzed using the dry modulus but installed in a 50 % RH environment, the predicted deflection is lower than actual by approximately 1.4× to 1.6× at constant load. Conversely, using conditioned tensile strength for a dry, cold-flex application overstates ductility. Notched impact behavior follows the opposite direction: the conditioned state absorbs more energy before crack initiation because water plasticizes the polyamide matrix and reduces the local yield stress at the notch root. The practical result is that dry-state Charpy values may reject a part that is actually functional in a humid vehicle cabin.

Long-term deformation should not be extrapolated linearly from the short-term modulus. ISO 899-1 creep testing at 80 °C and 30 MPa tensile stress is recommended for structural brackets. Published creep modulus data for this exact ESD formulation is limited, so design calculations should apply a creep factor of 0.55 to 0.65 to the conditioned tensile modulus for 1000 h load durations in preliminary sizing, with prototype validation required before dimensional release. This is a conservative engineering practice rather than a manufacturer-guaranteed limit.

Processing Window, Screw Geometry, and Fiber-Attrition Control

Injection molding production should start with pellets dried to 0.10 % maximum moisture using a desiccant dryer with a dew point of -30 °C or lower. Drying at 80 °C for 4–6 h is typical, but 60 min drying at the same temperature is insufficient for material exposed to ambient humidity above 60 % RH. Wet pellets produce surface splay, reduce molecular weight by hydrolysis, and can shift surface resistivity upward by interfering with contact between conductive particles. A 20:1 to 25:1 L/D general-purpose screw with a short compression zone and a reverse-flow check valve is adequate for production. The melt temperature should be maintained between 240 °C and 270 °C; the lower limit is dictated by viscosity and glass-fiber flow orientation, while the upper limit is set by PA12 thermal degradation and the risk of forming visible black specks or degrading the dissipative additive. Residence time at 270 °C should not exceed 10 min, and in hot-runner manifolds heated above 260 °C, the shutdown purge procedure should use the matrix polymer of the same PA12 family to avoid carbonized deposits.

A mold temperature of 60–90 °C is recommended to balance surface gloss, shrinkage, and ESD uniformity. Mold temperatures below 60 °C tend to produce higher frozen-in orientation and a more anisotropic shrinkage profile. Back pressure should be limited to 2–5 MPa hydraulic. Higher back pressure increases fiber attrition in the screw compression zone, which can reduce tensile strength by 5–10 % and change the surface resistivity from 10⁶ Ω into the 10¹⁰ Ω range if the fiber network disrupts the conductive particle percolation. Fiber attrition from pellet to molded part is typically 15–25 % by ash content comparison at 600 °C; gate geometry and runner diameter have a larger effect on attrition than melt temperature within the recommended range. In thin-wall sections below 1.0 mm, injection speed should be increased to avoid premature freeze-off, but shear rates above 30,000 s⁻¹ at the gate can cause local temperature spikes and resin degradation.

Welding-line strength in glass-reinforced ESD materials is a known processing constraint. The tensile strength at a knit line is typically 40–50 % of the unfused value, and the local surface resistivity may increase by one order of magnitude because glass fibers align parallel to the weld plane and reduce conductive particle contact across the interface. Multiple gates or complex core geometries should be prototyped with sequential valve-gate control when weld lines fall in areas subjected to bending or snap-fit assembly. Mold-flow simulation without ESD-specific viscosity data should be used only for cavity balance, not for weld-line strength prediction.

When pellets are stored in silos or open bins at ambient humidity above 60 % RH, moisture uptake occurs within hours. Drying time should be extended to 8 h at 80 °C if the starting moisture exceeds 0.20 %. A dew-point meter on the dryer outlet is more informative than time alone; dew point below -30 °C indicates the desiccant bed is functioning. If the dryer dew point rises above -20 °C, the bed should be regenerated before processing.

When Electrostatic Discharge Control Is Required in Chemically Aggressive Vehicle Environments

This grade is used in fuel-system retention clips, sensor brackets, connector housings, and conveyor components where the part must dissipate electrostatic charge while retaining dimensional stability in contact with nonpolar hydrocarbons. The PA12 backbone absorbs less moisture than PA6 or PA66 at equilibrium; unreinforced PA66 absorbs approximately 2.5 % and unreinforced PA6 approximately 3.0 % at 23 °C / 50 % RH, whereas the PA12-GF30 ESD grade remains near 0.5 % conditioned. This difference reduces the humidity-driven expansion and electrical property drift that can occur in coastal vehicle terminals or electronic enclosures. The trade-off is thermal: the heat deflection temperature under 1.80 MPa is approximately 165 °C dry, whereas a comparable PA66-GF30 ESD grade typically exceeds 240 °C. For continuous service above 120 °C, the PA66 alternative is mechanically preferable, unless the assembly is exposed to zinc chloride road salt, where PA12 has a known stress-cracking resistance advantage.

The static-dissipative function is measured by surface resistivity using IEC 62631-3-2 with a concentric ring electrode configuration at 100 V after 15 s electrification. The material typically falls in the range 10⁶–10⁹ Ω conditioned, which satisfies the process-safe ESD packaging requirement of IEC 61340-5-1 for dissipative materials below 1 × 10¹¹ Ω. It is not a conductive compound below 1 × 10⁴ Ω; therefore, it should not be specified for grounding paths or for applications requiring a low-resistance shield with direct contact to a functional earth. The dissipative property is bulk-distributed; machined holes, wear surfaces, and color variations in the black compound do not remove the ESD function in the way that an antistatic coating can be scratched or abraded.

Compared with a carbon black-filled PA12 without glass fiber, the glass-reinforced ESD grade raises tensile modulus from roughly 1800–2500 MPa to 8500 MPa dry, which allows thinner wall sections and higher clamp-load retention in threaded inserts. The penalty is anisotropy and a more complex shrinkage field. For mold design, linear shrinkage parallel to flow is approximately 0.2–0.4 %, while transverse shrinkage is typically 0.6–0.9 %. Unfilled conductive PA12 may shrink more uniformly around 1.0–1.5 %, but it has lower creep resistance and greater warpage under clamp load. The glass-filled ESD material also has better dimensional stability in fuel vapor environments; this is used in clips where loosening due to moisture or thermal cycling would create rattle noise or seal leakage.

Against a PA66-GF30 ESD compound, the PA12 grade has a lower density, approximately 1.25 g/cm³, versus 1.35–1.40 g/cm³ for PA66-GF30. This yields a 7–11 % mass reduction at equal wall section. The PA12 grade also retains lower moisture uptake, but its HDT under 1.80 MPa is 70–80 °C lower. The choice is therefore governed by the maximum service temperature and chemical exposure: fuel-system clips under hood with occasional short excursions to 140 °C may still be acceptable if the part is unstressed or supported, but continuous load at that temperature is not recommended.

Quality-control programs should verify glass content by thermogravimetric analysis or muffle furnace ash at 600 °C, with an acceptance window of 30 % ± 2 % by weight. A 1 % shift in glass weight fraction changes tensile modulus by approximately 200 MPa and can alter cavity fill in thin-wall sections. Melt mass-flow rate should be measured according to ISO 1133-1 at 275 °C / 5 kg; comparison against the virgin pellet value provides a sensitive indicator of regrind degradation or moisture damage. Regrind levels up to 20 % by weight in a homogeneous blend with virgin pellets typically show no measurable loss of surface resistivity, but higher levels may increase viscosity and require revalidation of melt-flow rate and tensile modulus.

Electrical property testing should be performed after conditioning the molded plaques or parts at 23 °C / 50 % RH for at least 48 h. Testing immediately after demolding is not representative because mold-release agents and residual surface moisture can lower the measured resistance by forming a temporary conductive film. Conversely, testing parts with heavy dust or handling contamination may produce artificially high values. The measured surface resistivity of a dissipative material is voltage- and time-dependent; the reporting of test voltage and electrification time is mandatory for meaningful comparison between lots.

Mold design should anticipate anisotropic shrinkage and the need for uniform melt-front advancement. Three-plate cold-runner systems are generally preferred over valve-gated hot runners when the part has small internal dimensions and can tolerate a small tunnel gate witness. If a hot runner is required, the manifold and nozzle tips should be specified for glass-filled abrasive compounds; standard copper-alloy nozzles may wear after 100,000 cycles and create metal contamination that affects spark-test or electrical resistance. Wear-resistant steel or hardened inserts at the gate land are recommended.

For regulatory documentation, the material can be specified against RoHS Directive 2011/65/EU and REACH candidate-list obligations for electrical and electronic equipment housings. Automotive OEM material standards often require additional data on outgassing, odor, or media compatibility; those documents must be requested from the manufacturer because the ESD additive package is not automatically covered by generic unfilled PA12 food-contact or drinking-water certifications. Compliance with IEC 61340-5-1 is not a fixed batch property; it depends on the final molded surface, contamination level, and conditioning history.

Operational boundaries include continuous hot-water contact above 80 °C, which accelerates hydrolysis and reduces molecular weight; strong mineral acids and halogenated solvents should be evaluated by immersion testing according to ISO 175 before use. The recommended maximum continuous service temperature in air is approximately 90–120 °C depending on load and exposure duration. Above this range, oxidative embrittlement becomes the limiting failure mode, not short-term heat distortion. The material is not recommended for direct sunlight exposure over multi-year service without UV-stabilized black pigmentation; severe UV environments require weathering validation according to ISO 4892-2 with color and surface resistivity monitoring. No additional stabilization beyond the standard grade should be assumed.