Barlog Plastics KEBABLEND M 11/24 PA12 is a polyamide 12-based ready-to-process compound for plastic-bonded permanent magnets produced by injection molding and, where gate or cavity geometry requires, transfer or compression molding. The M 11/24 designation belongs to the KEBABLEND magnet-grade range; the suffix encodes a specific ferrite or rare-earth filler system and a flow-modification package. The exact filler mass fraction, melt volume-flow rate, magnetic remanence, coercivity, and maximum energy product are manufacturer-controlled certificate-of-analysis parameters. In net-shape magnetic-component manufacturing, the material is used for annular encoder rings, wheel-speed sensor targets, rotor position magnets, and small fractional-horsepower motor stators. Incoming material audits normally include density according to ISO 1183-1:2019, melt volume-flow rate according to ISO 1133-1:2022, tensile properties according to ISO 527-2:2012, and magnetic characterization according to IEC 60404-8-1:2023.

Compared with neat polyamide 12 feedstocks, KEBABLEND M 11/24 is not an unfilled resin. The compound contains a dispersed ferromagnetic filler phase at a volume fraction sufficient to produce measurable remanence after magnetization. The polyamide 12 matrix is selected in bonded-magnet applications because its equilibrium water absorption is lower than that of PA6 under ISO 62:2008 conditioning. Reduced water uptake lowers ring-diameter growth in moist automotive wheel-end environments and reduces the risk of hydrolysis-induced molecular weight loss during melt processing. Pre-drying remains mandatory. Residual moisture content above 0.1 % before melt processing can produce splay, localized porosity at the magnet pole faces, and inconsistent melt viscosity. Desiccant dry-air drying at 80 °C for 4 h with a dew point of -40 °C is a production-scale starting condition; residual moisture should be confirmed by Karl Fischer titration before batch release.

What Limits the Injection Molding Window for PA12-Based Bonded Magnet Feedstocks?

Process development for KEBABLEND M 11/24 PA12 centers on balancing the low melt temperature of the polyamide 12 binder against the rapid solidification caused by the thermally conductive magnetic filler. On injection molding machines with screw diameters from 25 mm to 40 mm and L/D ratios from 18:1 to 22:1, the nozzle melt temperature is typically maintained between 220 °C and 260 °C. The lower limit is set by incomplete melting and poor filler wetting; the upper limit is set by amide-linkage degradation and release of volatile decomposition products. A flat or slightly reverse temperature profile in the metering zone is preferred at high filler loading because excessive shear heating can raise the actual melt temperature above the barrel set point. On a 30 mm screw running at 120 rpm, shear heating of 10 K to 20 K above the set barrel temperature can occur; screw speed should be adjusted using a nozzle melt thermocouple rather than barrel temperature alone.

Injection speed and gate geometry directly influence jetting and weld-line magnetic field distortion. Small subgates below 1.0 mm encourage premature freeze-off and orient filler along a narrow flow front, which can reduce radial remanence in annular multipole magnets. Full-round or fan gates from 1.2 mm to 1.8 mm diameter are generally used for cold-runner tools. Hot-runner valve gates should have hardened needle strokes and tip isolation designed for abrasive magnet compound. Mold temperatures between 60 °C and 90 °C are used to slow crystallization sufficiently for packing and to stabilize post-molding shrinkage. If mold temperature falls below 50 °C, high filler thermal conductivity quenches the melt and produces weld lines with pronounced filler depletion at the surface. Hot-runner manifolds should avoid dead spots where filler can stagnate and degrade; manifold temperatures should be profiled up to the gate, with the gate temperature not exceeding 260 °C. Heated tips above 280 °C can degrade the binder at the gate interface and cause gate blush or localized splay.

Standard reciprocating screw machines with screw diameters above 40 mm and shot sizes less than 25 % of barrel capacity can create long residence time. High filler content can obscure melt homogeneity while the PA12 matrix degrades if residence time exceeds 10 min at melt temperature. The machine should be purged with a filled PA12 purging compound before shutdown to remove magnetic filler from the check ring and screw channels.

At the time of writing, public data for this exact M 11/24 configuration is limited; the ranges above represent established processing practice for PA12-bonded ferrite compounds and should be verified against Barlog Plastics process recommendations.

The magnetic function of KEBABLEND M 11/24 PA12 is evaluated only after magnetization. Molded magnet rings are typically magnetized in a capacitor-discharge impulse magnetizer; the resulting pole-pair geometry is measured by a flux-coil scanning system or a pole-diameter integrated fluxmeter. Acceptance criteria are expressed as remanence B_r, coercivity H_cJ, and maximum energy product (BH)_max. Because the compound is polymer-bonded rather than sintered, the magnetic properties are lower than fully dense sintered ferrite or NdFeB. The binder occupies volume that cannot contribute to magnetic moment. Injection molding nevertheless enables multipole magnetization patterns and direct mechanical integration with shafts, hubs, or encoder wheels. A finished component can combine a magnetic ring with an insert-molded geometry in one step, which is not possible with sintered magnets without secondary bonding.

Because the magnetic filler increases thermal conductivity, cooling time is often shorter than neat PA12 at the same wall thickness, but this creates larger shrinkage differences between thick and thin sections. Tools with wall-thickness transitions should use generous radii, and gate location should avoid filling the magnetic pole area last. In a multipole encoder ring, the gate should be placed on a non-functional flange or hub, not on the outside diameter that will be magnetized. If the gate vestige or weld line lies between poles, the local filler orientation may produce a flux pattern with a missing-pole signature. This is a key difference from structural PA12 molding, where weld lines are assessed mainly by short-term strength.

Isotropic ferrite-filled PA12 compounds are magnetized after molding; the magnetization field strength must exceed the coercivity of the filler. Magnetizers with a charging voltage sufficient to generate 2.5 T to 3.0 T at the pole surface are common for ferrite-based bonded magnets. For rare-earth-filled PA12, saturation may require fields above 5.0 T, which demands specialized high-energy magnetizing fixtures. If the magnetizer current rise time is too slow or the fixture does not enclose the ring, not all domains orient fully, and the part fails remanence even if the material is within specification. Production lines therefore run a periodic flux audit rather than relying only on pellet properties.

Binder Selection Across PA12, PA6 and PPS Feedstock Grades

The primary technical difference between KEBABLEND M 11/24 PA12 and PA6-based magnetic compounds is moisture-driven dimensional drift. Under ISO 62:2008 conditioning at 23 °C and 50 % relative humidity, PA6 absorbs more water than PA12, which alters ring diameter, wall thickness, and press-fit force in automotive sensor applications. PA12 grades are therefore preferred for components that must pass thermal-humidity cycling with narrow radial air gaps. PA6 may provide higher dry tensile strength and higher heat deflection temperature in some formulations, but the penalty is greater post-molding dimensional change and higher moisture sensitivity during processing.

Compared with polyphenylene sulfide (PPS) bonded-magnet compounds, PA12 has a lower continuous-use temperature ceiling and lower chemical resistance, but a significantly lower mold temperature requirement. PPS compounds typically require mold temperatures above 130 °C and melt temperatures above 300 °C; PA12 can be processed at mold temperatures below 100 °C. This reduces tooling thermal expansion, auxiliary heater cost, and cooling time in multi-cavity production. PPS remains appropriate for continuous use above 150 °C or for exposure to hot automotive transmission fluid. For e-mobility sensors and interior motor feedback devices, PA12 offers a workable balance of melt processability and dimensional stability.

The values in the table are typical class-level data from polymer literature; they are not KEBABLEND M 11/24 grade-specific values. Barlog Plastics certificate of analysis and material datasheet control the actual specification.

Lot-to-lot magnetic filler particle size distribution is a stronger determinant of molded magnetic properties than melt flow rate alone. A shift in the mean particle size or specific surface area changes the maximum packing fraction and therefore cavity fill pressure. If the filler D90 increases, the melt may exhibit higher apparent viscosity at low shear rates; if the D50 decreases below the range for which the binder was optimized, agglomerates can form and reduce remanence. Production-scale compounding relies on twin-screw extruders with controlled shear and temperature profiles to disperse the magnetic filler without degrading the PA12 matrix. Incoming raw-material audits should include particle-size analysis by laser diffraction, dry-moisture analysis, and magnetic powder density, in addition to melt flow-rate testing.

When High Filler Loads Approach the Solid-Liquid Transition Limit

KEBABLEND M 11/24 PA12 is formulated for high magnetic filler loading because remanence and energy product increase with the volume fraction of magnetically active phase. As filler volume fraction increases toward the maximum packing fraction, the compound moves from a melt-like to a paste-like rheological response. Spiral-flow length drops rapidly and injection pressure increases. In this regime, wall slip, filler migration, and dead zones in the screw become process risks. Molding trials should record injection pressure at constant injection speed and compare spiral-flow length at a fixed wall thickness, such as 2.0 mm. If pressure exceeds 160 MPa to 200 MPa in a 2.0 mm spiral mold, venting and gate sizing are likely inadequate, or the melt temperature is too low. Such pressures are not unusual for high-load magnetic feedstocks, but they require a machine with adequate clamp force and no flash at the parting line.

Tool wear is also relevant. The magnetic filler phase is abrasive. Soft nitrided steel barrels and screws without surface hardening can lose screw diameter in the compression zone after continuous production. Bimetallic barrels and hard-faced screws in the compression and metering zones are recommended. Check-ring valves should be hardened and of the non-return type to prevent backflow. Mold inserts and gates should be hardened to at least 52 HRC where possible. Wear debris from screw/barrel contact can contaminate the magnetic powder and reduce local flux consistency.

For reliable production, solid-state drying is coupled with hopper dry-air blanketing. Once a sealed bag is opened, the material should be used within 8 h in a controlled environment; if not, re-drying at 80 °C for 4 h is required. Hopper retention times of 30 min to 60 min at 80 °C are acceptable for initial drying. PA12 can pick up moisture rapidly under high humidity; a hopper dry-air blanket with a dew point below -30 °C prevents surface moisture re-adsorption before entering the feed throat.

For automotive wheel-speed sensor rings, KEBABLEND M 11/24 PA12 can be overmolded onto steel or aluminum inserts. The ring OD is commonly toleranced to ISO 286-2 IT9 for diameters between 50 mm and 100 mm; air gaps between the encoder ring and Hall sensor are often specified below 1.0 mm depending on the module design. Because PA12 has a coefficient of linear thermal expansion higher than steel, the press-fit and radial air gap must be validated across the full thermal shock profile. A common validation sequence uses 500 cycles from -40 °C to 125 °C for the assembly, with post-test flux measurement according to IEC 60404-8-1:2023. Cracking after thermal cycling usually appears at the insert interface if the insert has not been preheated to 80 °C to 120 °C before overmolding or if the mold temperature is too low. Preheating the insert reduces residual tensile stress in the PA12 skin and increases the critical crack length at the boundary.

In seat-adjustment motors and HVAC actuators, the material is used for encoder rings and rotor magnets where multipole magnetization and low mass are required. The limit is not magnetic output alone, but the ability of the component to maintain flux output after exposure to vibration, humidity, and thermal ageing. Published data for this specific M 11/24 configuration in these applications is limited; design verification should include aged flux retention at 85 °C and 85 % relative humidity for 1000 h, following automotive component specifications derived from IEC 60068-2-67. The material must be tested for the intended pole-pair count because thin wall sections between magnetized poles can become irreversibly demagnetized at elevated temperature if the operating point falls below the knee of the BH curve.