Barlog Plastics KEBABLEND M 10/26 PA12 is a thermoplastic polyamide 12 carrier compound developed for injection-moulded plastic-bonded permanent magnets. The grade combines a PA12 binder with a magnetically hard filler system and is supplied as free-flowing granules for conventional reciprocating-screw injection moulding machines. The alphanumeric grade designation M 10/26 identifies the magnet-grade product configuration within the KEBABLEND portfolio; because filler particle size distribution and binder ratio govern melt rheology and magnetic output, the batch certificate from Barlog Plastics should be consulted for lot-specific filler content.

Plastic-bonded magnets based on PA12 are specified for net-shape encoder rings, automotive wheel-speed sensor targets, rotor magnet rings for brushless DC motors, and actuator feedback rings. In these applications the component is typically overmoulded onto a steel shaft or insert and magnetised after ejection in a multi-pole pattern using a capacitor-discharge magnetiser. The PA12 carrier provides lower equilibrium moisture uptake than PA6 when evaluated according to ISO 62:2008 and retains low-temperature impact behaviour below 0 °C in notched Charpy testing according to ISO 179-1:2010. These properties support dimensional stability in humid environments and reduce the risk of brittle fracture during press-fit assembly.

Which Process Parameters Govern Reliable Injection Moulding of Magnet-Filled PA12?

Predrying is executed at 80 °C until residual moisture falls below 0.1 % by mass; moisture content is verified by ISO 15512:2019 Karl Fischer titration. Incompletely dried PA12 magnetic compounds can show splay, viscosity fluctuation, and hydrolysis-induced molecular weight loss. Drying time is normally 4–6 h in a desiccant dryer with a dew point of −30 °C or lower; hopper residence time should be limited so that dried granules do not rehydrate.

The melt-temperature window for PA12-bonded magnet compounds typically lies between 230 °C and 270 °C. Below 220 °C, high filler content produces an abrupt viscosity increase and freeze-off in thin walls; above 270 °C, thermal degradation of the polyamide backbone accelerates. Lot-specific recommendations for KEBABLEND M 10/26 PA12 may narrow this window, especially at maximum filler loading, and should be taken from the manufacturer’s lot card. Mould temperature is generally maintained at 60–100 °C using oil or pressurised water heating. Higher mould temperatures improve weld-line strength and reduce frozen-in orientation but increase cycle time.

Injection speed is set in the medium-to-high range, commonly 100–300 mm/s screw advance depending on machine size, because the magnetic filler increases thermal conductivity and solidifies the melt more rapidly than unfilled PA12. Slow injection causes flow marks, hesitation lines, and non-uniform filler distribution. Hold pressure must be maintained until gate freeze; magnet-filled PA12 has lower melt compressibility and often requires longer hold times than unfilled PA12. Screw recovery should use low back pressure, typically 0.5–2.0 MPa, to avoid excessive filler breakage and melt-temperature overshoot.

Production-scale experience with abrasive magnet compounds shows progressive wear of screw flights, barrel wall, and check ring when standard nitrided steel components are used. Three-zone screws with L/D ratios of 20:1 to 25:1, compression ratios of 1.8:1 to 2.2:1, and bimetallic barrels or hard-chrome flight coatings are specified. Non-return ring failures are a known bottleneck; a hardened ring with full-contact seat is preferred. Published data for this specific configuration is limited, so qualification runs should monitor melt viscosity and magnetic property drift over 10,000 cycles.

On production-scale equipment, a thin-wall encoder ring with wall thickness of 1.5 mm and outer diameter of 30–60 mm can be moulded on an 80–120 t hydraulic injection moulding machine with an 8-cavity cold-runner tool. Observed cycle times for PA12 magnet compounds in this geometry are typically 25–35 s; gate freeze time rather than cooling time often limits the cycle. Premature gate freeze is the dominant failure mode when runner diameter is below 2.5 mm, because the filled melt solidifies faster than unfilled PA12. Multi-cavity tools require independent gate balance within ±2 % cavity-to-cavity weight variation to avoid angular flux variation.

Magnetic characterisation of injection-moulded KEBABLEND M 10/26 PA12 parts is performed after magnetisation in a capacitor-discharge magnetiser. For isotropic ferrite-filled PA12 systems, representative remanence values fall between 240 mT and 290 mT, intrinsic coercivity between 160 kA/m and 240 kA/m, and maximum energy product between 9 kJ/m³ and 13 kJ/m³ when measured according to IEC 60404-5. These ranges are material-class reference values, not a guaranteed product specification. The exact magnetic output of this grade is determined by filler volume fraction, part density, frozen filler orientation, and cross-section; lot-specific demagnetisation curves must be requested from the manufacturer for motor-design calculations.

If the compound is anisotropic, moulding without a magnetic orientation field yields only a fraction of the available remanence. The grade designation M 10/26 alone does not confirm isotropy or anisotropy. Multi-pole magnetisation of encoder rings is normally performed with pole counts from 4 to 32. Capacitor-discharge magnetisers used for multi-pole rings often operate in the 1,000–4,000 V range with pulse durations below 10 ms; incomplete saturation appears as reduced peak flux density and increased angular error. The magnetising fixture must match the part’s outer diameter and pole pitch to within ±0.05 mm for uniform magnetisation.

Dimensional Stability, Water Uptake, and Mechanical Property Boundaries

The PA12 binder in KEBABLEND M 10/26 PA12 provides lower water absorption than PA6-based magnet compounds. At equilibrium in 23 °C and 50 % relative humidity, PA12 absorbs approximately 0.7 % water by mass; PA6 absorbs approximately 2.5 % when tested according to ISO 62:2008. Because the magnetic filler displaces resin, the absolute moisture uptake of the filled compound is lower than that of the unfilled carrier. This difference reduces dimensional growth and magnetic air-gap drift in humid environments.

Coefficient of linear thermal expansion for magnet-filled PA12 compounds typically falls between 30 × 10⁻⁶ K⁻¹ and 50 × 10⁻⁶ K⁻¹ in the flow direction, and between 40 × 10⁻⁶ K⁻¹ and 70 × 10⁻⁶ K⁻¹ transverse to flow, measured between 23 °C and 80 °C by ISO 11359-2:2021. Shrinkage anisotropy must be considered when dimensioning encoder rings, because unfavourable gate location can produce ovality exceeding 0.1 mm on parts with outer diameters above 40 mm.

Tensile stress at break of representative ferrite-filled PA12 compounds lies in the range 40–65 MPa according to ISO 527-1:2019, while flexural modulus is between 8,000 MPa and 14,000 MPa according to ISO 178:2019. Elongation at break is typically below 2 %, making the material notch-sensitive. Notched Charpy impact strength at 23 °C is commonly 2–6 kJ/m² according to ISO 179-1:2010. These mechanical boundaries require generous radii, draft angles of at least 1°, and balanced ejection to prevent demoulding cracks in thin magnet rings.

Heat deflection temperature under 1.8 MPa loading generally falls between 120 °C and 170 °C for PA12-bonded ferrite systems according to ISO 75-2:2013. Continuous use above this range is not recommended because PA12 softens and magnetic performance may shift with temperature; grade-specific thermal ageing data should be requested.

When PA12-Based Bonded Magnet Compounds Replace PA6, PPS, or Thermoset Binders

Selection of KEBABLEND M 10/26 PA12 over a PA6-based magnet compound is justified when humidity-induced dimensional drift must be controlled. The lower water uptake of PA12 compared with PA6 reduces swelling in encoder rings exposed to engine-compartment condensation. The trade-off is lower heat deflection temperature; PA6 grades often maintain higher stiffness at temperatures above 150 °C, while PA12-bonded ferrite systems approach their upper service limit near 120–150 °C under load.

Compared with PPS-based bonded magnet compounds, PA12 permits lower barrel temperatures of 230–270 °C rather than 300–340 °C, reducing energy input and enabling less aggressive tool thermal-management requirements. PPS retains superior continuous-use temperature and chemical resistance, but its higher mould temperature requirement and higher melt viscosity make thin-wall multi-pole rings more difficult to fill without flow hesitation. PA12 also offers lower melt viscosity at equivalent filler volume fraction, which can improve filling of long thin sensor rings.

Against thermoset epoxy-bonded magnet systems, thermoplastic injection moulding provides faster cycles, recyclable sprues and runners, and the ability to overmould shafts, bearings, and sensor targets in one step. Thermoset epoxy can accept higher filler loading and often shows better high-temperature dimensional stability, but it cannot be reground and requires longer cure cycles. The choice of a thermoplastic PA12 compound is therefore process-driven: complex geometry, insert moulding, and cycle-time reduction.

Relative to PA11-based magnet compounds, PA12 generally has lower water absorption and a slightly higher melting temperature, but both aliphatic polyamides are processable on the same equipment. The choice is often supplier-specific because both provide low water uptake compared with PA6.

Table 1. Comparative property envelope for ferrite-filled bonded magnet compounds; values are compiled from public supplier datasheets and do not constitute a batch-specific specification for KEBABLEND M 10/26 PA12.

Regulatory verification for KEBABLEND M 10/26 PA12 should include current REACH candidate list screening, RoHS Directive 2011/65/EU Annex II compliance for homogeneous materials, and automotive IMDS submission according to the customer’s PPAP level. Ferrite-based magnetic fillers are generally RoHS-compliant; rare-earth fillers may require declaration of heavy-metal impurities. No food-contact or medical-grade claim should be inferred from the PA12 base unless a specific Barlog Plastics written declaration exists.

Operational boundaries are defined by the polyamide 12 matrix. Continuous exposure to strong acids, hot concentrated glycols, or steam above 80 °C can hydrolyse the binder and reduce mechanical strength. The compound is not recommended for continuous-use temperatures above 120–150 °C under load, depending on the specific filler system. Storage should be in sealed, moisture-tight containers at 5–30 °C; prolonged storage at high humidity requires re-drying before processing.

Abrasive Wear Concentrates at Gate, Runner, and Cavity Surfaces

Tooling for KEBABLEND M 10/26 PA12 magnet rings is subject to abrasive wear at the gate, runner, and cavity surfaces. Hardened hot-work tool steels with nitriding or PVD coating are specified for production volumes above 100,000 cycles; uncoated soft steels can show dimensional drift from wear after 10,000–20,000 shots. Gates should be placed to minimise jetting and flow weld lines; tunnel or film gates are preferred for multi-pole rings because they reduce gate vestige and improve roundness.

The screw and barrel should be inspected at intervals no greater than 100,000 cycles for abrasive wear. Pullback and recovery time increases indicate check-ring leakage or screw wear. The hopper should be fitted with a desiccant dryer and a magnetic grille or drawer magnet to remove ferrous contamination, but this does not replace a wear-protected screw.

Regrind generated from sprues, runners, and rejected parts may be reused at controlled levels. Because the magnetic filler can oxidise or degrade with repeated thermal histories, the maximum regrind ratio is defined by the customer’s qualification programme. In multi-pole encoder rings, excessive regrind can shift magnetic output and increase porosity; melt viscosity and demagnetisation testing after regrind are recommended.