Barlog Plastics KEBABLEND M FE 120202/20 PA12 for plastic-bonded magnets belongs to a class of ferrite-filled polyamide 12 compounds developed for isotropic injection-molded magnet bodies. The binder is selected because equilibrium moisture absorption remains below 1.5 wt% at 23 °C and 50% RH per ISO 62, which limits post-molding dimensional drift after magnetization. Typical production grades for isotropic plastic-bonded magnets carry 86–93 wt% ferrite; the exact filler fraction of this grade is defined by the manufacturer and is not restated where published data is limited. The application scenarios below describe processing practice, formulation windows, compliance documentation, and end products for magnet bodies produced from this material class, with test methods and equipment specifications stated where they define the processing window.

Passenger vehicle anti-lock braking system encoder rings are produced as multi-pole magnetized rings that are pressed onto wheel bearing seals. For this application a PA12-bonded ferrite compound of this class is processed with a ferrite fraction of 88–91 wt% and a PA12 binder fraction of 9–12 wt%, with 0.5–1.0 wt% of internal lubricant and heat stabilizer added to reduce screw torque and prevent binder oxidation at the nozzle. Compliance evidence for series release normally includes Directive 2000/53/EC end-of-life vehicle requirements, Directive 2011/65/EU Annex II restricted substance limits, and IATF 16949:2016 clause 8.5.1.1 control plan documentation for automotive safety-related parts. Processing on a 2-platen injection molding machine with a 4-cavity cold runner tool and tunnel gates at the inner diameter uses nozzle melt temperature 260–280 °C, mold wall temperature 80–110 °C, injection speed 80–120 mm/s, and holding pressure 60–80 MPa. The ring is demolded with a central steel bush insert and magnetized in a capacitor discharge fixture to 32–96 poles. The magnetized flux density at the sensing point is inspected with a Hall probe at 0.5 mm air gap, with a typical acceptance range of ±5% from the nominal batch reference. Batch-to-batch variance is controlled by maintaining magnetic powder lot traceability and by monitoring compound melt volume-flow rate at 275 °C and 5 kg load in the range 8–20 cm³/10 min per ISO 1133-1.

When Ferrite Loading Exceeds 88 wt% in PA12 Melt Streams

When the ferrite mass fraction is raised above 88 wt%, the melt leaves the Newtonian plateau and exhibits shear thinning with a power-law index between 0.35 and 0.50 at 1,000 s⁻¹. Pressure drop across a cold sprue of 4 mm diameter can exceed 40 MPa at a fill time of 0.8 s. Rotor position sensor rings for electric power steering and e-bike motors are molded from isotropic ferrite-filled PA12 with 90–92 wt% ferrite and 8–10 wt% PA12. Because no magnetic alignment field is applied during injection, remanence remains in the range 240–270 mT, coercivity H_cB in the range 170–190 kA/m, and coercivity H_cJ in the range 200–260 kA/m when measured on cylindrical test pieces per IEC 60404-5. The components are magnetized after ejection as 8–12-pole rings with a pole-to-pole flux density variation of less than ±2% measured at 0.5 mm air gap. Processing requires a bimetallic barrel and screw with L/D 18:1–20:1 and compression ratio 1.8:1. A tungsten carbide check ring and hardened nozzle tip are specified because ferrite at 90 wt% creates abrasive wear at the non-return valve within 40,000–60,000 cycles; replacement intervals are monitored by shot weight drift and short-shot mass. Melt cushion is held at 3–5 mm, back pressure at 0.5–1.0 MPa, and nozzle temperature at 265–285 °C. If the melt cushion drops below 2 mm, cavity packing becomes unstable and magnetized flux density can fall by 5–10% because unfused ferrite particles create local porosity. Hot runner systems with 6 mm minimum channel diameter and thermally insulated gates are used only when validated by pressure transducer monitoring; otherwise cold runners with 6–8 mm diameter are preferred. The table below summarizes the process parameter window and the dominant failure mode outside the window.

Industrial linear encoder disks for motion control systems require a wall thickness of 1.0–2.0 mm and a flatness deviation below 0.05 mm after magnetization. To achieve spiral flow lengths of 60–80 mm at 80 MPa injection pressure, the PA12-bonded ferrite compound is diluted to a ferrite fraction of 86–88 wt% with a binder fraction of 12–14 wt%. Processing uses a 2-cavity mold with a center film gate, vacuum venting at 0.02–0.03 mm, mold wall temperature 120–140 °C, and injection speed of 100–150 mm/s to prevent premature freeze-off in thin sections. The part is ejected after a holding time of 8–12 s and placed on a flat cooling fixture to control post-ejection warpage. Compliance for industrial automation components is documented through Directive 2011/65/EU Annex II, Regulation (EC) No 1907/2006 Article 33, and ISO 9001:2015 clause 8.5.1 for traceability of the magnetic filler batch. The disk is magnetized with 64–128-pole tracks in a multi-pole magnetizing fixture; the pole pitch is verified by Hall probe scanning per IEC 60404-8-1. End products include rotary encoders on servo motors and linear position scales on machine tool axes.

Is Pre-Drying Always Necessary for PA12-Bonded Ferrite Compounds?

For solenoid actuator pole pieces and magnetic return structures in fluid control valves, pre-drying is applied if opened bag storage exceeds 2 h at >60% RH or if the material is transferred through an open hopper. PA12 absorbs less water than PA6, but ferrite surfaces adsorb moisture; a residual moisture level above 0.10 wt% measured by ISO 15512 generates surface splay and reduces melt strength during processing at 250–270 °C. Drying in a desiccant dryer at 80 °C for 4 h to 0.08 wt% or lower is used before molding. The compound is molded with 90–92 wt% ferrite and 8–10 wt% PA12, with melt temperature 250–270 °C, mold temperature 80–100 °C, and injection speed 60–100 mm/s. The pole piece is insert-molded over a brass armature with a 0.2–0.4 mm interference layer; insert temperature is held at 120 °C to reduce shrinkage stress. Magnetization is carried out after cooling with a saturating field of at least 1,200 kA/m applied in a capacitor discharge fixture, which is sufficient to reach at least 95% of the remanence plateau for isotropic ferrite. Material compliance documentation references UL 94 HB flame class and Directive 2011/65/EU Annex II. End products include pilot-operated solenoid valves for washing machines and industrial fluid control manifolds.

For magnetically coupled pump rotors, the compound must balance magnetic output against chemical resistance to weak acids, alkaline detergents, and hydrocarbon-based process fluids at operating temperatures up to 80 °C. The rotor rings are molded with 89–92 wt% strontium ferrite and 8–11 wt% PA12; because the magnet ring is fully encapsulated within a thermoplastic housing, direct chemical contact with the binder is limited. Rotor rings are magnetized as 4-pole or 8-pole assemblies, with pole count selected by the coupling torque constant and air gap. Thick-section rotor rings with wall thickness 10–20 mm require a hold time of 15–20 s per 10 mm wall thickness and mold wall temperature 100–120 °C to reduce sink marks and internal voids. Process validation includes X-ray or micro-CT inspection for porosity below 2 vol% in the magnet ring, with ISO 3452-1 penetrant testing for surface cracks after demolding. Compliance follows Directive 2014/34/EU ATEX only at the final pump assembly level; the magnet compound itself is not an ATEX component, but the magnet temperature coefficient is characterized per IEC 61807. End products include sealless chemical dosing pump drive rotors and magnetic mixers for laboratory reactors.

Consumer Sensor Magnet Carriers and Lid Detection Assemblies

In laptop lid detection and stylus docking sensors, flat magnet carriers of 1.2–2.0 mm thickness are injection molded from PA12-bonded ferrite with 88–90 wt% filler and 10–12 wt% binder. The mold is a 4-cavity tool with pin gates at the part edge, mold wall temperature 100–120 °C, melt temperature 260–280 °C, and cycle time 20–30 s. Documentation includes Directive 2011/65/EU Annex II and Regulation (EC) No 1907/2006 Article 33; no food-contact or medical-grade documentation is required for this application. The carrier is magnetized as a 2-pole bar with unipolar field profile verified at 1.0 mm air gap. End products include lid-closed detection sensors and stylus charging cradle alignment magnets.