Polyamide 6 and 66 Impact Modification: Notched Izod Loss at Sub-Zero Temperatures

In unfilled and short-glass-reinforced polyamide 6 and polyamide 66 injection-moulding compounds, Asahi Kasei Tuftec™ MP10 is melt-blended at 8–15 wt% for PA6 and 10–20 wt% for PA66 as a starting-point range when the specification requires ductile failure at −30 °C under notched Izod per ISO 180:2023 Method 1A. The maleic anhydride groups participate in ring-opening reactions with terminal primary amine groups on the polyamide chain, generating a graft/block copolymeric interphase that arrests crack propagation. Published data for lot-specific MP10 acid value and its influence on PA66 molecular weight retention is limited; therefore, torque-rheometry trials on a laboratory twin-screw extruder are used to establish the upper loading before production scale-up.

Compounding is typically performed on a co-rotating twin-screw extruder with L/D ratio 40:1 to 48:1 and barrel profile of 230–260 °C for PA6 and 270–300 °C for PA66. Glass fibre, when specified at 30 wt%, is side-fed after the reactive melting zone so that the anhydride-amine reaction proceeds before fibre attrition becomes severe. Vacuum venting at −0.08 MPa or lower is applied after the reaction zone to strip residual moisture and volatile oligomers. Moisture in the polyamide before compounding must be reduced to ≤0.15 wt% for PA6 and ≤0.10 wt% for PA66, verified by ISO 15512:2019 Karl Fischer titration, otherwise the compounded pellets exhibit surface porosity and downstream injection-moulding delamination.

Specimens for ISO testing are prepared according to ISO 294-1:2017 and conditioned at 23 °C/50 % RH for 24 h prior to destructive evaluation. The relevant property set includes notched Izod per ISO 180:2023, tensile yield strength and elongation at break per ISO 527-2:2012 Type 1A, flexural modulus per ISO 178:2019, and heat deflection temperature under 1.8 MPa per ISO 75-2:2013 Method A. Terminal components produced from MP10-modified PA6/PA66 grades include automotive under-hood brackets, power-tool motor housings, industrial castors, cable glands, and electrical connector shells. For applications where food contact is relevant, the grade-specific FDA 21 CFR 177.1810 documentation must be reviewed, because the maleic anhydride modification may impose additional migration-testing constraints under EU 10/2011.

Operational boundaries are narrow when PA66 is processed above 300 °C: oxidative yellowing and anhydride deactivation occur simultaneously, and the notched Izod gain at −40 °C can fall relative to material compounded below 295 °C. This threshold behaviour is batch-to-batch dependent; melt-pressure readings at the die are monitored because an abrupt pressure rise indicates excessive graft reaction and potential screen-pack blinding.

These windows are indicative starting-point ranges compiled from general maleated SEBS formulation practice and require confirmation against the specific lot certificate, matrix viscosity, and filler surface chemistry. They are not supplier guarantees.

Thin-wall electrical connectors moulded from polybutylene terephthalate require impact modification that does not reduce glow-wire ignition resistance; Tuftec™ MP10 is incorporated at 5–12 wt% in PBT and 8–15 wt% in PET-based compounds for this purpose. Above 15 wt% in PBT the flexural modulus falls steeply, and the crystallization half-time measured by differential scanning calorimetry can increase sufficiently to cause ejection difficulties at cycle times below 25 s. The anhydride functionality reacts with terminal hydroxyl and carboxyl groups on the polyester chain; therefore, residual moisture competes with the desired esterification reaction and hydrolyses the matrix. Pre-drying in a dehumidifying hopper drier with dew point ≤ −40 °C at 121 °C for 4 h is required for PBT, while PET is dried at 130–150 °C to ≤0.005 wt% moisture.

Melt compounding is performed on a co-rotating twin-screw extruder with barrel profile 240–260 °C for PBT and 270–290 °C for PET, with a vacuum vent at −0.08 MPa after the second kneading zone. For glass-fibre-reinforced grades, short glass fibre at 20–30 wt% is side-fed after the MP10 dispersion zone; this sequence prevents the fibre from shielding the anhydride reaction sites. Melt temperature at the die is kept below 270 °C for PBT and 290 °C for PET. Exceeding these limits generates tetrahydrofuran and acetaldehyde by-products, creates die-lip deposits, and reduces the notched Izod improvement below the value expected from a properly vented system.

Compliance testing for PBT connectors typically references ISO 180:2023 for notched Izod at −30 °C, ISO 527-2:2012 Type 1A for tensile properties, ISO 75-2:2013 Method A for heat deflection temperature, and IEC 60695-2-11:2014 for glow-wire ignition resistance when the component is used in unattended electrical equipment. Terminal product types include relay sockets, automotive fuse boxes, EV charging inlet housings, circuit-breaker components, and power-window gear cases. In each case, the modified compound must be processed within the stated moisture and melt-temperature boundaries; otherwise the terminal part exhibits nozzle-side hydrolysis streaks and a reduction in glow-wire performance.

What Limits Impact Retention in PPE/PA Alloys When MP10 Content Falls Below 7 wt%?

In polyphenylene ether/polyamide alloys used for exterior automotive panels, Tuftec™ MP10 functions as a reactive interface modifier because the styrene-containing SEBS backbone preferentially locates within the PPE phase while the anhydride group reacts with the polyamide phase. At loading below 7 wt%, the compatibilized interphase is too sparse to prevent coalescence of the PPE domains; notched impact values at −20 °C become unstable across moulding batches, and scanning electron microscopy of cryofractured surfaces reveals phase-domain diameters above 3 µm. Starting-point loading is 7–12 wt% in unfilled PPE/PA6 and 5–10 wt% in PPE/PA66 when combined with 20–25 wt% short glass fibre. Published data specific to MP10 in PPE/PA66 is limited; the stated range is an indicative formulation window used for laboratory screening, not a supplier-guaranteed specification.

Compounding is carried out in a two-stage sequence to avoid localized amine-anhydride gelation. In the first stage, MP10 is pre-dispersed in polyphenylene ether at 290–310 °C on a high-free-volume twin-screw extruder; in the second stage, polyamide and glass fibre are introduced into a downstream side feeder or secondary extruder. The full barrel profile is 280–310 °C, and vacuum venting at −0.08 MPa removes moisture carried by the polyamide. Melt-pressure signals monitored before the die must remain stable; pressure fluctuations above ±0.3 MPa typically indicate phase inversion or poor side-feed incorporation. The extruder screw contains a short first mixing zone, a long reaction zone with narrow-kneading discs, and a low-shear pumping zone to limit PPE thermo-oxidative degradation.

Property evaluation follows ISO 6603-2:2000 for instrumented puncture impact, ISO 179-1:2010 for Charpy edgewise impact, ISO 527-2:2012 for tensile modulus, and ISO 306:2022 for Vicat softening temperature. Terminal products include painted automotive fenders, mirror housings, rear quarter-panel supports, and under-bonnet structural brackets where the alloy must retain impact resistance after e-coat bake cycles at 180–200 °C. Because MP10-containing PPE/PA alloys are hygroscopic, moisture-conditioned injection-moulded parts must equilibrate at 23 °C/50 % RH for at least 48 h before comparison testing; otherwise the PA phase contributes artificially high ductility.

Two-component injection moulding of soft-touch grips onto polyamide housings requires a SEBS/PP/oil TPE compound that can bond without a solvent primer; Tuftec™ MP10 is added at 10–20 wt% to provide that reactive interphase. The compound typically contains 20–30 wt% polypropylene, 35–50 wt% paraffinic white oil, and a non-functionalised SEBS balance, although exact proportions depend on target hardness and oil migration limits. The maleic anhydride groups of MP10 react with amine end groups on the polyamide surface during the overmoulding shot, forming a covalent interphase that resists peel and shear. Adhesion is evaluated by ISO 813:2019 90° peel testing of the overmoulded TPE strip at 100 mm/min; a cohesive TPE failure indicates sufficient interphase strength, while adhesive separation at the interface indicates underreaction caused by wet substrate or low mould temperature.

Pre-compounding of the TPE is run on a co-rotating twin-screw extruder at 180–210 °C with the MP10 added in the main throat and the oil side-injected after the initial SEBS/PP melting zone to prevent lubricated screw slippage. The two-component moulding process then injects the TPE at 190–230 °C onto a polyamide substrate that is either moulded in the same cycle or pre-heated to 80–120 °C. Mould surface temperature for the overmoulding station is held at 30–60 °C; below this range the interfacial reaction freezes before interdiffusion, and above 80 °C the TPE may exhibit surface tack and extended cooling time. The polyamide substrate must be dried to ≤0.10 wt% moisture and kept free of mould release, because silicone- or wax-based mould releases block the amine groups and reduce peel strength.

End-use specifications for power tools and household appliances may require the overmoulded assembly to pass drop testing, oil resistance, and peel adhesion values above 2.5 N/mm, but published industry limits vary by OEM and substrate condition. Terminal products include power-tool soft grips, garden-tool handles, kitchen knife handles, personal-care appliance grips, and hand-tool overmoulds. Where the article contacts skin, the final compound must meet REACH 1907/2006 and the applicable polycyclic aromatic hydrocarbon limits under AfPS GS 2019:01 PAK, while for food-contact utensils the grade-specific FDA and EU 10/2011 migration documentation must be verified separately.

When Halogen-Free Cable Compounds Approach 65 wt% Filler Loading

In low-smoke, halogen-free flame-retardant cable insulation and sheathing based on EVA/LDPE or polyolefin elastomer matrices, Tuftec™ MP10 is used at 3–8 wt% to modify the filler-matrix interface when the combined aluminium trihydroxide and magnesium dihydroxide loading reaches 60–65 wt%. The maleic anhydride functionality reacts with surface hydroxyl groups on the metal hydrate particles, reducing filler-filler agglomeration and improving elongation at break after flame-retardant addition. Without a reactive maleated SEBS, such compounds can drop below 125 % elongation at break and fail the cable deformation or tensile requirements. Published data for MP10 in specific cable formulations is limited; the stated addition window is an indicative starting point that must be tuned for filler particle size, silane surface treatment, and base polymer melt index.

Compounding is performed on a twin-screw extruder or Buss co-kneader with a temperature profile of 160–190 °C and a maximum melt temperature of 200 °C to avoid aluminium trihydroxide decomposition, which releases water vapour and causes foaming. Magnesium dihydroxide permits a higher melt ceiling, but the combined system is constrained by the ATH fraction. The filler is side-fed in two stages to avoid torque spikes, while MP10 is added in the main throat with the base polymers. Vacuum venting at −0.07 MPa or lower is applied in the final barrel section. Die pressure is monitored to detect filler agglomeration; pressure fluctuations above ±0.2 MPa at the strand die indicate poor dispersion and highlight the need to adjust screw speed or oil addition.

Flammability testing follows IEC 60332-1-2 for single-wire vertical flame propagation, IEC 60754-1/-2 for halogen acid gas evolution and pH/conductivity, and IEC 61034-2 for smoke density when cables are specified for public buildings. Tensile properties of the crosslinked or thermoplastic sheathing are evaluated per ISO 527-2:2012 Type 5A, and hot-set or long-term ageing may be required under EN 50363 for insulation and sheathing compounds. Terminal products include low-voltage building wire, solar photovoltaic cable jackets, EV charging cable sheathing, and halogen-free control cables for rail interiors. Because MP10 does not impart flame retardancy by itself, the total filler loading and flame-retardant synergist package must remain the primary design lever; MP10 is not a substitute for ATH/MDH or intumescent additives.