EMS-Grivory Grilamid® L 25 W 40 ESD is a black, carbon-black-modified polyamide 12 (PA12) compound supplied for injection moulding and extrusion of components requiring permanent electrostatic dissipation. The product identity comprises the Grilamid L PA12 backbone, a high-viscosity profile indicated by the 25 designation, a W 40 modifier package, and an ESD package that lowers surface resistance relative to unfilled PA12. The grade is normally pigmented black because the conductive filler is carbon black; colour alternatives are not specified for the ESD designation. Moulded test specimens are characterised under ISO 1183-1 for density, ISO 527-1/-2 for tensile properties, ISO 179/1eA for notched Charpy impact, and ANSI/ESD STM11.11 or IEC 61340-2-3 for surface resistance. Typical application areas include fuel line retainers, electrical connector housings, sensor brackets, conveyor rollers, and clips where static charge accumulation must be controlled. The PA12 base contributes lower saturated water uptake and less moisture-induced dimensional movement than PA6 or PA66 compounds. Surface resistivity is positioned in the dissipative range, commonly 10⁶ to 10⁹ Ω at 23 ± 2 °C and 50 ± 5 % relative humidity. Volume resistivity is usually reported between 10² and 10⁵ Ω·cm according to IEC 60093. Unfilled PA12 grades typically show surface resistance above 10¹² Ω and can accumulate static charge rapidly. Because conductivity is generated by a percolating carbon-black network, final resistance depends on mould geometry, processing history, and moisture conditioning. The material is dissipative rather than conductive; it is not intended to carry fault current or replace a metallic grounding path.

What Limits the Conductive Network in Carbon-Black-Modified PA12?

Three processing and formulation variables control ESD behaviour in this grade: filler loading, dispersion quality, and post-moulding moisture uptake. Near the percolation threshold, small differences in carbon-black concentration can produce large shifts in resistivity. Production-scale compounding on twin-screw extruders with L/D ratios of 40:1 to 52:1 is therefore monitored by melt pressure, screw torque, and pellet resistivity checks. Excessive shear or extended residence time can over-disperse carbon black and break conductive pathways, increasing surface resistance by one to two decades. Insufficient dispersion leaves carbon-black agglomerates that act as local insulating zones. On injection moulding lines, surface resistance is frequently tested with a 2.27 kg probe assembly according to ANSI/ESD STM11.11. Measurements taken at gate areas and weld lines may differ from bulk surfaces by up to one decade if the conductive network is oriented, diluted, or ruptured during cavity filling. Field observations from production lines indicate that weld lines are a recurrent failure mode for ESD parts. When two melt fronts meet, carbon-black network continuity can be locally reduced. The resulting weld-line resistance is not fixed and varies with melt temperature, mould wall temperature, injection velocity, and gate position. Valve-gated hot-runner systems can shift weld lines away from the discharge path between the component surface and a grounded attachment point. For critical electrostatic dissipation properties, parts should be tested after moulding, after conditioning, and after any secondary operation such as ultrasonic welding, machining, or plasma treatment. Representative property values are summarised below. Tensile and thermal data are reported for dry as-moulded samples; electrical data are recorded after 48 h at 23 ± 2 °C and 50 ± 5 % relative humidity.

Property	Test standard	Typical range	Condition
Density	ISO 1183-1	1.12–1.13 g/cm³	dry
Tensile modulus	ISO 527-1/-2	1500–1900 MPa	dry
Yield stress	ISO 527-1/-2	35–45 MPa	dry
Nominal strain at break	ISO 527-1/-2	>20 %	dry
Charpy notched impact, 23 °C	ISO 179/1eA	5–10 kJ/m²	dry
Charpy notched impact, -30 °C	ISO 179/1eA	3–7 kJ/m²	dry
Melting point, DSC	ISO 11357-1/-3	175–180 °C	dry
Heat deflection temperature, 1.8 MPa	ISO 75-1/-2	45–55 °C	dry
Heat deflection temperature, 0.45 MPa	ISO 75-1/-2	110–120 °C	dry
Surface resistivity	ANSI/ESD STM11.11	106–109 Ω	23 °C/50 % RH
Volume resistivity	IEC 60093	102–105 Ω·cm	23 °C/50 % RH
Water absorption, 24 h	ISO 62	0.1–0.2 %	23 °C
Moulding shrinkage	ISO 294-4	0.6–1.0 %	parallel

The values above are representative and are not a substitute for lot-specific certificate of analysis data or part-level validation. Carbon-black loading and molecular weight are controlled within manufacturing tolerances, and electrical data may shift after heat ageing, fuel contact, or repeated mechanical loading. The tensile modulus is below that of a 30 % glass-fibre PA66 ESD compound, but the PA12 grade provides higher notched impact at low temperature and reduced moisture-related dimensional change.

Pre-Drying and Melt Processing Variables for Injection Moulding and Extrusion

Moisture control is the first process variable. Although PA12 absorbs less water than PA6 or PA66, melt processing at moisture levels above 0.10 % can produce surface splay, dimensional instability, and hydrolytic molecular weight loss. Pre-drying in a desiccant dryer at 80 °C to 90 °C for 4 h to 6 h is recommended. The dryer should maintain a dew point of ≤ -30 °C. Hopper residence times above 1 h at elevated temperature may cause discoloration and should be avoided. Regrind should be dried under the same conditions before processing. For injection moulding, the melt temperature window is 230 °C to 270 °C. Mould wall temperature is normally set between 60 °C and 100 °C; higher mould temperatures within this range improve weld-line strength and resistance uniformity. Melt temperatures above 280 °C can degrade the conductive network and increase volatile emissions. Injection speed is usually held at low to medium settings to limit shear-induced filler network breakdown.

Processing parameter	Typical range	Comment
Drying temperature	80–90 °C	desiccant dryer
Drying time	4–6 h	new granulate
Melt temperature	230–270 °C	injection moulding
Mould temperature	60–100 °C	higher for ESD uniformity
Injection speed	low to medium	reduce shear damage
Screw geometry	compression ratio 2.0:1–2.5:1	general purpose
Regrind addition	≤20–30 %	validate ESD after addition

Extrusion of rods, tubes, or profiles from this grade should use a screw with a compression ratio of 2.0:1 to 2.5:1 and a melt pump where cross-section tolerances are tighter than ±0.05 mm. On production lines, shear-induced resistance drift is a known bottleneck. When screw speed is increased to raise throughput, the metering-zone barrel temperature is often reduced by 5 °C to 10 °C to maintain constant melt viscosity and reduce over-shear. Hot runners should be externally heated to avoid stagnant polymer that can undergo thermal degradation and release carbon-black agglomerates. All hoppers, grinders, and conveying lines should be grounded to prevent pre-mould static charging.

Gate Placement and Weld-Line Resistance in Carbon-Black-Filled PA12

Gate location influences resistance distribution more strongly in carbon-black-filled ESD materials than in unfilled polyamide. The conductive filler orients during fountain flow, and the outer skin of a moulded part can differ in resistivity from the core. Edge gates and restrictive fan gates may create high-resistance zones near the gate if the melt is excessively sheared. Wall thickness transitions from 1.5 mm to 4.0 mm should avoid abrupt steps because carbon-black orientation at transitions can form high-resistance bands. Mould trials on 1,200 kN to 2,500 kN injection machines indicate that short injection time and moderate packing pressure help preserve network integrity; excessive packing pressure above 60 MPa hydraulic does not necessarily reduce resistance and may increase mould flash risk. Weld lines should be positioned away from the electrical path between the component surface and a grounded holder or discharge point. Sequential valve gate control is used in multi-cavity tools to move weld lines into non-critical areas. Moulds should be vented adequately because carbon-black-filled melts can generate volatiles that condense on tool surfaces and locally increase surface resistivity. Hardened tool steel is recommended; carbon black is abrasive and can accelerate gate and core wear. In fuel line retainers and sensor housings, the PA12 matrix provides low swelling in mineral oils, greases, and automotive fuels. The grade is often evaluated after immersion in ASTM reference fuels; tensile strength retention is generally higher than unfilled PA6 and standard PA66 grades, although published data for this specific ESD formulation in ethanol-blended fuels is limited. Electrical connector housings made from the grade are used in automated assembly where surface resistance below 10⁹ Ω prevents damage to voltage-sensitive devices. Conveyor rollers benefit from the combination of low moisture shift and dissipative surface resistance, but abrasive wear of carbon-black-filled PA12 can generate black particulate. Cleanroom applications require wear testing under ISO 5470-1 or an equivalent abrasion standard before release.

When Low Moisture Absorption and Low-Temperature Impact Favourably Compare with PA66 ESD

Compared with glass-reinforced PA66 ESD grades, Grilamid L 25 W 40 ESD offers lower tensile strength and lower heat deflection temperature but better low-temperature impact and lower moisture sensitivity. PA66 ESD compounds often exhibit dry tensile strengths above 150 MPa; this PA12 grade is not a direct substitute for high-strength structural brackets. For clips, snap-fits, and housings where thermal loads remain below 80 °C, the PA12 grade reduces the risk of brittle failure at -40 °C. Compared with unfilled PA12, the ESD grade has reduced elongation at break and slightly higher melt viscosity because of the carbon-black loading. Compared with a lower-viscosity Grilamid L 20 ESD or similar high-flow ESD grade, the L 25 W 40 ESD variant is specified where higher melt strength or improved impact resistance is required. However, thin-wall sections below 0.8 mm may require higher melt temperatures or faster injection speeds, and published comparative spiral-flow data for the specific W 40 formulation is limited. Against ESD polyacetal grades, PA12 offers better resistance to certain alkaline and moisture environments but lower creep resistance. Against ESD polypropylene compounds, PA12 provides higher upper service temperature and better fuel resistance, but at higher material cost and with higher moisture uptake. Material substitution therefore requires part-level verification of thermal endurance, chemical exposure, and electrostatic decay after conditioning.

Compliance and Handling Boundaries

RoHS compliance is typically declared under Directive 2011/65/EU for the ten restricted substances. The grade does not contain polybrominated biphenyls or polybrominated diphenyl ethers. REACH SVHC declarations must be obtained from the material supplier for the specific production lot because carbon-black feedstock and processing aids can vary. The product is not supplied with implantable medical-grade documentation. Electrical properties are not guaranteed on painted, coated, plasma-treated, or machined surfaces; surface resistivity must be re-verified after secondary operations. Parts should not be exposed to strong oxidising acids or high-pressure steam above 110 °C. Long-term UV exposure can cause surface chalking and slight shifts in surface resistivity. Waste incineration must follow local regulations; carbon-black-filled polymer retains heat and may require controlled feed rates. For production quality control, lot-to-lot resistivity variation is commonly checked on a compression-moulded plaque of 100 mm × 100 mm × 2 mm. Surface resistivity is measured at five points under ANSI/ESD STM11.11. If lot resistivity approaches 10⁹ Ω, the risk of failing charge-decay requirements increases. Charge decay testing under IEC 61340-2-1 is often performed by corona charging to 5 kV and recording the time from 1 kV to 100 V; dissipative materials should decay within 2 s. When changing from PA66 to this PA12 grade, thorough purging is required because residual PA66 can cause delamination or reduce impact strength.