EMS-Grivory Grilamid L XE 4074 black 9225 is a polyamide 12 injection-molding compound filled with 40 wt% glass beads and supplied in black color number 9225. The EMS designation places the grade in the L polyamide 12 family; XE identifies glass bead reinforcement, and 4074 defines the filler and additive package. The term "Conditioned" is not a separate product variant but a moisture state. Specimens conditioned to ISO 1110 or stored at 23 °C/50 % RH under ISO 62 absorb water into the amorphous phase, lowering glass transition and modifying tensile, impact, and creep response relative to dry-as-molded specimens. Published EMS-Grivory technical data give a dry density of approximately 1.29 g/cm³ by ISO 1183-1, and molded shrinkage of approximately 0.6 % to 0.8 % for 2 mm plaques by ISO 294-4.

The filler geometry is analytically significant. Glass beads have an aspect ratio close to unity, so they do not orient strongly in the shear field during injection. Packing and cooling therefore dominate residual stress development rather than flow-induced fiber alignment. On production machines with clamp capacities from 80 t to 120 t and screw diameters from 25 mm to 35 mm, the grade molds with relatively low anisotropic shrinkage, but gate freeze time is shorter than unfilled PA12 because the bead-filled melt freezes quickly. Parts with wall thickness below 0.8 mm require high injection speed, typically above 200 mm/s, to avoid premature freeze-off; published process data for this specific thickness configuration is limited.

What Limits the Melt Processing Window in a Glass Bead-Filled PA12 Grade?

The lower bound is set by the PA12 crystalline melting point at 175–180 °C by ISO 11357-3. Feed zone settings below 220 °C may produce unmelted granules and glass bead agglomerates because effective melt viscosity is high. The upper bound is limited by amide bond oxidation. Barrel profiles from feed to nozzle are commonly set between 220 °C and 270 °C; melt temperatures above 280 °C cause visible yellowing and molecular weight loss. The use of glass beads rather than glass fibers reduces shear heating, but erosion of screw flights, check ring, and nozzle tip occurs because hard silica-based filler slides across metal surfaces. Screw peripheral speed is kept below 0.3 m/s; higher speeds do not typically degrade the melt first but accelerate wear, especially at the check ring.

Mold temperature is the second critical variable. At 40 °C, a quenched amorphous skin forms quickly and can restrict packing in thin sections; at 80–90 °C, skin thickness is reduced and pressure transmission improves. Hold pressure is typically 50–80 MPa, with packing time of 2–4 s/mm wall thickness. Cooling time for a 3 mm wall is approximately 15–25 s; glass beads increase thermal conductivity relative to unfilled PA12, but the exact reduction in cooling time depends on mold steel, coolant temperature, and part geometry. Hot-runner valve gates are preferred over small open gate tips; gate diameter should be at least 1.5 mm to prevent bead jamming and excessive gate shear. On production-scale injection molding lines, the most common failure mode is not melt degradation but gate blush and surface roughness caused by glass beads migrating to the surface during high-speed injection. Reducing injection velocity below 100 mm/s for large gates and increasing mold temperature to 80 °C often reduces surface defects. Another observed effect is check ring leakage when the screw and barrel wear; this causes shot weight variation above 0.3 %. Replacement intervals for bimetallic screw and barrel assemblies are shorter than for unfilled PA12 because the glass beads are abrasive.

Drying, Moisture Conditioning, and the Dry-As-Molded Discrepancy

PA12 absorbs moisture more slowly than PA6 or PA66 because of its longer aliphatic chain and lower amide group density. Nevertheless, pellet surface moisture at processing can cause hydrolysis and splay. EMS processing documentation for polyamide 12 grades recommends pre-drying at 80 °C for 4–6 h in a desiccant dryer with a dew point below -20 °C after storage in open containers for more than 30 min at 23 °C/50 % RH. Residual moisture at the machine feed throat above 0.10 % by weight is associated with viscosity reduction and notched impact loss. A hot-air hopper dryer alone is insufficient when ambient relative humidity exceeds 60 %; desiccant drying is required.

The dry-as-molded state is not stable in service. After ejection, specimens and parts take up water from humid air. At 23 °C/50 % RH, a 3 mm thick plaque approaches equilibrium moisture content on a timescale of weeks, not hours, because moisture diffusion in PA12 follows Fickian kinetics with concentration-dependent diffusivity. Accelerated conditioning under ISO 1110 at 70 °C/62 % RH accelerates this. Water in the amorphous phase acts as a plasticizer; the glass transition temperature of dry PA12 is near 50–60 °C by ISO 11357-2, but in the conditioned state it can fall below 0 °C. This shift explains why conditioned tensile modulus and yield stress are lower, while elongation at yield and notched impact rise.

When Moisture Conditioning Suppresses Yield Stress in PA12

The mechanical response of this grade is dominated by the glass bead interphase and the plasticized matrix. In dry specimens, the matrix is stiff and relatively brittle under tensile deformation; in conditioned specimens, the matrix yields more readily, so tensile modulus declines from approximately 3500 MPa to 2500 MPa by ISO 527-1/-2. Tensile stress at yield drops from approximately 50 MPa to 34 MPa, while tensile strain at yield increases from about 5 % to 14 %. The glass beads themselves are rigid and do not absorb moisture; the property shift arises from the matrix. Notched Charpy impact at 23 °C by ISO 179-1/1eA increases from about 5 kJ/m² dry to 7 kJ/m² conditioned. At -30 °C, the conditioned gain is smaller because matrix mobility is reduced.

Differences from unfilled PA12 are most visible in stiffness and dimensional stability. Unfilled PA12 has a dry tensile modulus near 1400–1600 MPa by ISO 527-1/-2; the glass bead-filled grade raises this to approximately 3500 MPa. However, the same filler reduces notched impact and may reduce weld-line strength because beads concentrate stress at the interphase. Flow-weld lines in glass bead-filled grades show strength retention of roughly 50–70 % of bulk yield, depending on melt temperature and mold temperature; published data for this specific color and conditioning state is limited.

Compared with short glass fiber reinforced PA12, the glass bead grade provides lower tensile modulus and strength but lower anisotropic shrinkage. A short glass fiber PA12 may show flow shrinkage below 0.2 % and transverse shrinkage above 1.0 % in 2 mm plaques; this difference drives warpage. The glass bead grade keeps flow and transverse shrinkage within 0.2 percentage points, enabling flat parts with dimensional tolerances below 0.05 mm/mm in some gated geometries. This is the main technical rationale for selecting XE 4074 over a fiber grade: not maximum mechanical strength, but predictable geometry.

Capillary rheometry for glass bead-filled PA12 shows pronounced shear thinning above 100 s⁻¹. The beads increase low-shear viscosity but contribute negligible melt elasticity because of spherical shape. In mold-filling simulation, a Cross-WLF or Herschel-Bulkley viscosity model calibrated from capillary data is needed; generic unfilled PA12 coefficients underpredict fill pressure in gates where shear rates exceed 10,000 s⁻¹. Published capillary viscosity data for this exact grade and color is limited; processing simulations should use material data from the EMS-Grivory database or direct capillary testing.

Creep data for glass bead-filled PA12 are more limited than short-term tensile data. Bead-filled grades generally show lower creep resistance than glass fiber grades at the same filler weight fraction because spherical particles do not bridge cracks or retain orientation. Under sustained loads above 20 MPa at 23 °C, creep strain can accumulate progressively; design calculations should use creep modulus from ISO 899-1 or supplier-generated isochronous stress-strain curves, not short-term tensile modulus. Fatigue performance under cyclic loading is sensitive to weld lines, surface roughness, and moisture. Published fatigue data for this specific glass bead-filled PA12 configuration is limited; designers should not extrapolate from unfilled PA12 or glass fiber PA12.

PA12 itself has one of the lowest water absorption values among common polyamides, near 1.2–1.5 % saturation in water at 23 °C by ISO 62. The glass bead filler reduces the matrix fraction and therefore tends to lower total water uptake proportionally. Resistance to automotive fuels, oils, greases, and salt spray is generally strong for PA12, but continuous exposure to hot glycol, methanol, or strong acids should be evaluated against the EMS chemical resistance list for Grilamid L grades. No universal compatibility statement applies; stress-cracking resistance depends on chemical concentration, temperature, and molded-in stress.

EMS-Grivory material data sheets for this grade typically reference classification under ISO 1043-1, ISO 1874-1, and marking under ISO 11469. RoHS and REACH statements are declared on the supplier lot-specific certification; users should verify the black 9225 colorant package for food-contact or medical suitability because pigmented variants may not carry identical regulatory status to natural resin. The material should not be processed with regrind above 30 % without remixing and impact verification. Processing regrind above 30 % may reduce Charpy notched impact and increase variability; published data for this specific grade is limited. The recommended practice is to limit regrind to 20–30 % and keep hopper residence time below 30 min in humid environments.

The grade is suited to molded parts such as sensor housings, solenoid valve bodies, cable clips, and pneumatic manifolds where dimensional stability and moderate stiffness are required over a temperature range from -40 °C to 80 °C. In such parts, the design should avoid thin sections below 0.8 mm, sharp internal corners below 0.5 mm radius, and hot-weld lines in tensile load paths. If continuous operating temperature exceeds 90 °C or if the part is exposed to hot air for more than 1000 h, oxidative embrittlement of PA12 becomes a design constraint and an antioxidant-stabilized grade or alternative material should be considered.