Barlog Plastics KEBABLEND MW FE 190204 PA12 is classified as a polyamide 12-based injection moulding compound for magnetically active components. The grade designation combines the KEBABLEND trade name, the MW/FE family descriptor associated with magnetic filler technology, and the 190204 product code. Grade-specific values for filler type, filler loading, melt viscosity, mechanical properties, and magnetic polarisation must be obtained from the manufacturer’s batch datasheet. Published independent datasets for this specific configuration are limited; the review below therefore separates established PA12-bonded magnet behaviour from properties that must be verified on the delivered material.

Material qualification for this product family is normally structured around a standards matrix. The following methods are required for evaluating polymer-bonded hard magnetic compounds and are not themselves product specifications. Values should be measured on at least three production batches to establish lot-to-lot variation before release to a magnetising cell.

What materially separates a PA12-bonded magnetic grade from PA6, PA66, or PPS systems?

Unfilled PA12 absorbs approximately 1.5 wt% water at 23 °C saturation under ISO 62, whereas unfilled PA6 and PA66 absorb approximately 9–10 wt% and 8–9 wt%, respectively. At 50 % relative humidity, PA12 equilibrates near 0.7–1.0 wt%, while PA6 values commonly fall between 2.5 wt% and 3.0 wt%. The lower equilibrium moisture uptake reduces hygroscopic expansion and hydrolysis kinetics in the polyamide binder. For a magnetised rotor or sensor target, this results in a smaller geometric shift in the air gap between the magnetised surface and the field sensor after storage in an unsealed housing.

The melting and processing ranges also differ. Unfilled PA12 has a melting peak near 175–180 °C by ISO 11357-3. Filled PA12 magnetic compounds are typically processed at melt temperatures between 220 °C and 250 °C, which is below the 260–290 °C range used for many filled PA66 compounds and far below the 300–340 °C required for PPS-bonded magnets. The wider thermal distance from degradation permits lower mould temperatures, reduced energy input, and lower drying thermal load; however, it also limits continuous service at elevated temperature compared with PPS.

The magnetic filler in the MW/FE family is selected for hard magnetic behaviour; ferrite-based grades typically use strontium or barium ferrite, while higher-energy variants use neodymium-iron-boron or samarium-iron-nitrogen powders. Ferrite-filled PA12 offers moderate remanence but high electrical resistivity, a lower eddy-current loss in alternating fields, and a remanence temperature coefficient commonly reported near -0.2 %/K. Rare-earth-filled PA12 provides higher remanence but greater raw-material cost and stronger corrosion sensitivity if the filler is not fully encapsulated. The binder selection, not only the powder, determines whether the compound can be overmoulded onto steel pole rings without cracking during thermal cycling.

The difference between isotropic and anisotropic ferrite grades has a direct effect on maximum energy product and alignment strategy. Isotropic ferrite-filled compounds can be magnetised in a complex multi-pole pattern without a pre-alignment step; anisotropic fillers require orientation during moulding or a higher charging field, but they deliver a higher remanence. The KEBABLEND grade should be classified as either isotropic or anisotropic from the datasheet before magnetising fixture design.

PPS-bonded magnetic grades are selected when continuous service above 180 °C or aggressive chemical contact is present. PA12 should not be selected where the component is continuously soaked in hot gearbox oil above the heat deflection temperature of the filled grade. For ambient actuator, sensor, and hydrometer applications, PA12 provides lower mould temperature requirements, lower bulk density than PPS systems, and better dimensional stability in humid air than PA6 and PA66. The selection is therefore governed by service temperature, chemical exposure, mechanical load, and air-gap tolerance, not by magnetic filler chemistry alone.

On production scale, the most significant source of batch-to-batch magnetic deviation in PA12-bonded feedstock is not the raw magnet powder but the compounding sequence.

Co-rotating twin-screw extruders with an L/D ratio of 40 or higher are used to disperse ferrite or rare-earth filler into the PA12 melt. The polymer is fed into the main hopper; the magnetic filler is introduced through a downstream side feeder after the polymer has melted. This configuration limits filler fracture and reduces the time at high temperature. Melt temperature at the die is generally maintained below 250 °C because decomposition of silane or titanate coupling agents can weaken the filler-matrix interface. Vacuum devolatilisation is applied after filler addition to remove moisture and low-molecular-weight volatiles. Pellets are cooled in a water bath, dried to a moisture content below 0.1 wt%, and packed in foil-lined bags to prevent moisture regain.

Pre-drying before injection moulding is mandatory if storage relative humidity exceeds 60 %. A desiccant dryer with a dew point below -30 °C should be used. Drying at 80 °C for 4–8 h is typical for PA12 compounds; material from partly opened bags may require up to 12 h after high-humidity exposure. Residual moisture above 0.1 wt% produces surface defects, viscosity variation, and possible hydrolysis of the PA12 binder. The feed hopper should be blanketed with dry air at a dew point below -25 °C and should not remain open during stoppages.

Injection moulding parameters, gate design, and tool-wear control

For thick-section magnetic rotors, injection moulding is selected for short cycle time and repeatable fill. Cylinder profiles from rear to nozzle are typically set at 210–220 °C, 220–230 °C, 230–240 °C, and 240–250 °C. The mould temperature is normally maintained between 60 °C and 80 °C; lower mould temperatures of 40–50 °C may be used for thin-wall parts, but they reduce weld-line strength and increase frozen-in orientation. High injection speeds of 100–200 mm/s are generally required to prevent premature freeze-off. Back pressure should be kept between 0.5 MPa and 1.0 MPa to avoid over-shearing the magnetic filler. Holding pressure is typically set at 50–80 % of peak injection pressure to compensate for volumetric shrinkage; excessive holding pressure can create gate stress and cracking around magnetisable inserts.

Melt residence time is critical. The barrel volume should be matched to shot size so that the material does not reside in the plasticising unit for extended periods. In filled PA12, residence time above 10 min at melt temperature increases the risk of binder degradation and causes visible brown streaks. When the shot volume is below 25 % of barrel capacity, a smaller screw diameter or accumulator head is recommended. Start-up and shutdown purging should use a low-viscosity polyamide purge compound, not glass-filled material, to avoid abrasive wear of the barrel and screw.

Gate design must account for the high filler loading. Edge gates with a thickness of 50–70 % of the part wall and land lengths below 1.0 mm reduce shear heating and filler orientation at the gate. Tunnel and submarine gates are avoided for highly abrasive magnetic compounds because the gate insert wears quickly and the high shear rate can separate binder from filler. Multi-pin or fan gates are preferred for ring-shaped parts to produce a concentric melt front and reduce weld-line disturbance in the magnetised zone.

Tool wear is highest at the gate, runner, and cavity locations where melt direction changes. Filled PA12 compounds are abrasive; mould steels such as 1.2083 or 1.2344 ESR are normally specified for gate inserts and corner pins. Production experience with filled polyamides shows that maintenance intervals for gate inserts can be 30–50 % shorter than for unfilled PA12. Hardened surfaces below 52 HRC are not recommended in direct contact with the melt for production volumes above a few thousand cycles.

Mould-filling simulation for this product family should not rely on generic unfilled PA12 data. Viscosity curves measured by ISO 11443 and pressure-volume-temperature data measured by ISO 17744 are required for accurate pressure drop prediction. Generic neat PA12 inputs may underestimate pressure drop by a significant margin and can lead to short shots or gate freeze-off in high filler loading compounds. Shrinkage models should account for anisotropic filler orientation; moulded samples typically show lower shrinkage in the flow direction than transverse to flow.

Cavity pressure sensors installed near the gate and the last-fill position are used to detect viscosity shifts caused by moisture or filler segregation. The pressure integral from switch-over to gate freeze-off is monitored; a drift of more than 5–10 % from the qualified baseline should trigger a material audit. This practice is used on multi-cavity production tools to identify blocked gates or worn non-return valves before large numbers of defective magnetic parts are produced.

When thin-walled encoder rings are produced by injection-compression moulding

When part thickness drops below 2.0 mm and radial runout tolerance is below 0.05 mm, injection-compression moulding is used to reduce residual stress and improve filler distribution. The cavity is opened by a defined stroke during injection, then closed under controlled force. Compression force is set to avoid excessive flash while maintaining uniform density. Tool surface temperature should be held within ±5 °C of the selected setpoint; larger deviations produce non-uniform crystallisation and can distort the magnetised ring. Vacuum-assisted venting may be necessary because high filler loadings reduce vent capacity and can trap gas at the inner rim of a ring gate.

After moulding, components are magnetised in a fixture whose coil geometry is matched to the part diameter and pole count. The charging field is selected according to the coercivity of the magnetic filler; ferrite-filled PA12 is typically magnetised from 1.1 T upward, while rare-earth-filled systems may require fields above 2.5 T. The magnetising pulse duration is normally in the millisecond range, and the fixture is cooled if the production rate exceeds 10–15 cycles/min. Demagnetisation curves should be measured on finished parts rather than on raw pellets because orientation, weld lines, and gate geometry affect the final magnetic flux density. A Hall probe or fluxmeter with a Helmholtz coil is used for in-line quality control, against limits traceable to IEC 60404-4 and IEC 60404-8-1.

Operational boundaries for the PA12-based compound include continuous service above the heat deflection temperature of the filled grade being not recommended, prolonged contact with concentrated acids or hot polar solvents causing hydrolysis of the PA12 matrix, and combination with unapproved amine-based processing aids possibly altering the filler-polymer interface and reducing dispersion stability. If the material is stored in perforated bags or exposed to high humidity without resealing, the pre-drying time must be revalidated by ISO 15512 moisture measurement. For applications requiring electrical and electronic component compliance, the manufacturer’s REACH and RoHS statements under EC 1907/2006 and 2011/65/EU with delegated directive (EU) 2015/863 are the binding documents.