EMS-Grivory Grilamid XE 3817 black 9992 is a semi-crystalline polyamide 12 (PA12) grade supplied with heat stabilisation and impact modification. The black 9992 colour code is produced with a carbon black masterbatch that provides ultraviolet absorption and uniform pigmentation; the material is not reinforced with glass fibre or mineral filler. In the conditioned state, moisture content has been brought to equilibrium with 23 °C and 50 % relative humidity according to ISO 291, or accelerated to an equivalent level by ISO 1110. Conditioning is not an indication of hygroscopic saturation; it is a controlled water absorption step intended to produce reproducible toughness data. The material density is approximately 1.02 g/cm³ by ISO 1183, and saturation water uptake in water at 23 °C is approximately 1.4 % by ISO 62. Because the polymer backbone is polyamide 12, water absorption is lower than that of PA6 and PA66, and dimensional changes in humid service are correspondingly reduced.

PA12 occupies a specific position among engineering polyamides because the amide group concentration is lower than in PA6 or PA66. The lower amide concentration reduces hydrogen bonding sites for water and produces a material with lower density, lower equilibrium moisture content, and lower notch sensitivity at low temperature. The impact modifier in XE 3817 forms a dispersed elastomeric phase that increases energy absorption during crack initiation, but also lowers tensile modulus and hardness relative to an unmodified PA12. These are not processing defects; they are intended changes in the molecular and morphological balance. The grade is used in injection-moulded clips, cable ties, snap-fit fasteners, and extruded corrugated or smooth tubing. A conditioned PA12 grade such as XE 3817 provides lower moisture uptake than PA6 and retains measurable notched impact resistance at -30 °C.

How Does Moisture Conditioning Shift the Mechanical Response of Grilamid XE 3817?

Conditioning alters the mechanical response in two directions: absorbed water reduces stiffness and yield stress, and it increases notched impact strength. In dry-as-moulded condition, tensile modulus is typically in the upper part of the range 800–1000 MPa; after conditioning, the value drops to approximately 600–800 MPa when tested by ISO 527-1/-2. The yield stress moves from roughly 30–35 MPa to 22–28 MPa, while nominal strain at break remains above 50 %. This shift must be accounted for in snap-fit design; a clip designed only on dry modulus can lose insertion force or become under-constrained after moisture uptake. Notched Charpy impact strength by ISO 179-1/1eA at 23 °C is commonly reported in the range 25–45 kJ/m² after conditioning, and the material retains a notched impact value above 6 kJ/m² at -30 °C. The heat deflection temperature under 1.8 MPa load by ISO 75-1/-2 remains in the region of 45–55 °C, which places the grade below glass-filled PA12 and PA66 for elevated-temperature load-bearing service.

For the black 9992 variant, carbon black content can slightly reduce surface resistivity and alter thermal conductivity. If static dissipation is required, surface resistivity must be confirmed by IEC 60093 or ASTM D257 rather than assumed from pigmentation. The mould shrinkage range of 0.7–1.1 % in flow direction by ISO 294-4 is close to unfilled PA12, and differential shrinkage between flow and transverse directions can produce ovality in thin-walled circular parts if the gate is not centrally located. Parts with press-fit inserts should be assembled only after conditioning because the lower modulus reduces hoop stress and the risk of stress cracking. In dry-as-moulded condition, the same interference fit may produce cracks at the insert edge when the part is later exposed to road salt.

Rheological Boundaries and Equipment-Dependent Defect Patterns

Melt temperature control is the principal processing constraint. The grade is processed by injection moulding and extrusion with a melt temperature between 210 °C and 250 °C; operation above 250 °C for more than 10 min residence time can initiate thermal chain scission and black speck formation in carbon black-loaded PA12. A desiccant dryer should reduce moisture to ≤0.10 % before melting. Drying at 80 °C for 4–6 h with a dew point below -30 °C is typical; drying above 110 °C is not recommended because oxidation can shift colour and reduce impact resistance. In injection moulding, mould temperature should be held at 30–60 °C. The lower end produces faster cooling and higher skin orientation, which raises flow-direction modulus but increases frozen-in stress; the upper end improves crystallinity and dimensional stability at the expense of cycle time. A uniform mould temperature across the cavity is required because a thermal gradient greater than 10 K between opposing surfaces can cause bowing in clips longer than 80 mm.

On a hydraulic injection machine with clamp force between 600 kN and 1500 kN, a screw with L/D ratio from 20:1 to 25:1 and compression ratio 2.0:1–2.5:1 is used. Back pressure is typically 30–60 bar, and screw speed is set to avoid shear heating above 250 °C; melt temperature should be monitored at the nozzle because the shear heating contribution from a worn check ring can be 5–10 K higher than the barrel set point. If the non-return valve leaks, cushion instability and part mass variation exceed 0.5 %, and dimensional acceptance in snap-fit engagement features is lost. A recommended barrel profile for a 25 mm diameter screw is feed zone 200–210 °C, compression zone 220–230 °C, metering zone 230–240 °C, and nozzle 230–245 °C. Hot-runner manifolds should be kept below 250 °C and purged at start-up because PA12 can discolour at dead spots.

Extrusion of tubing requires a reverse temperature profile from the feed zone to the die, with maximum die head temperature 230–250 °C, and a polished calibrating die with vacuum sizing. A melt pump is recommended for wall thickness tolerance below ±0.05 mm. Moisture above 0.10 % causes splay, microvoids, and reduced burst pressure in pneumatic tubing; if ambient relative humidity exceeds 60 %, the dryer hopper should not be left open. Venting is critical because PA12 carbon black grades can generate volatile residuals; vent depths of 0.02–0.05 mm are common in injection moulds. If the vent is too deep, black flash occurs; if too shallow, burn marks form at the fill end. Reground XE 3817 black 9992 can be used, but the addition rate should not exceed 20 % if impact and surface finish requirements are tight; carbon black agglomerates from repeated processing can produce visible surface pitting and lower notched impact at -30 °C.

If the Application Requires Ductility at -30 °C and Resistance to Zinc Chloride, How Does This Grade Compare With PA6 and PA66?

At a wall thickness below 1.5 mm, rapid cooling in a cold-runner mould suppresses PA6 and PA66 crystallinity and can produce brittle fracture at sub-zero temperatures. PA12 retains ductility at lower temperature because its glass transition is lower and its methylene-rich chain reduces moisture sensitivity. XE 3817 in the conditioned state typically retains a notched Charpy impact value of 6–12 kJ/m² at -30 °C, whereas an unmodified PA6 conditioned at the same temperature may fall below 4 kJ/m² depending on molecular weight and mould temperature. In addition, PA12 withstands zinc chloride solutions and many automotive road salts, whereas PA6 and PA66 are susceptible to stress cracking in zinc chloride at concentrations as low as 30 %. This difference is used in wire clips and fuel-line retainers exposed to underbody conditions.

Compared with an unmodified PA12 such as Grilamid L 25, XE 3817 has a lower tensile modulus and higher notched impact strength. The trade-off is a reduction in hardness and abrasion resistance; a sliding wear application requiring high surface hardness should use a glass-filled or higher-viscosity PA12 grade. Compared with a 30 % glass-fibre-reinforced PA12, XE 3817 is not a structural replacement: typical reinforced grades exhibit tensile modulus above 7000 MPa, while XE 3817 conditioned remains below 800 MPa. The selection logic is therefore reversed: XE 3817 is chosen when the part must flex, snap, or absorb impact rather than carry high sustained loads.

Differences from PA66 also appear in thermal properties. PA66 has a melting point near 260 °C, requiring higher processing temperatures and creating greater energy input; XE 3817 melts at 174–178 °C, allowing lower mould temperatures and reduced cycle time. However, the PA12 base has a lower heat deflection temperature than a 30 % glass-filled PA66, which can exceed 240 °C. Therefore XE 3817 is not used under continuous load above 60 °C where creep or creep rupture may control design. In hot water or humid environments, PA12 typically retains a higher fraction of tensile strength than PA66 after extended exposure, but the lower stiffness of XE 3817 means that creep deformation can occur at lower stress than in reinforced polyamides.

Operational boundaries include the following: continuous service above 60 °C under mechanical load should be verified by creep testing because heat deflection temperature is below 55 °C; exposure to strong acids, phenol, cresol, or formic acid should be avoided; the black pigmentation may restrict food-contact use unless specific migration testing is performed under EU 10/2011 or FDA 21 CFR; the grade is not flame retardant and is typically classified as UL 94 HB at test thickness. For automotive fuel vapour applications, no single PA12 grade provides universal resistance to all oxygenated fuels; compatibility testing should follow SAE J2260 or ISO 7628 for tubing systems. Published data for this specific colour and lot combination in long-term hydrolytic ageing is limited, so end-users should request test reports from the compounder before specifying the material in safety-critical fluid handling.