Arkema Rilsamid AZM 23 BLACK T6LD is a thermoplastic polyamide 12 injection-moulding compound designated in ISO 1043-1 material shorthand as PA12-GF23. The formulation contains a nominal 23% by mass glass-fibre reinforcement dispersed in a heat-stabilised, lubricated, black compound. The suffix T6LD identifies the heat-stabilisation package, internal lubricant system, and dry-as-moulded supply condition of the grade. The material is supplied as pellets for conversion on conventional injection-moulding equipment with standard three-zone screws and general-purpose thermoplastic check rings. Because the system is based on polyamide 12 rather than polyamide 6 or polyamide 66, the grade exhibits a lower equilibrium moisture uptake under humid conditions, which reduces the dimensional change encountered in parts exposed to atmospheric humidity or under-bonnet thermal cycles. The product is used primarily in injection-moulded technical components requiring a balance of stiffness, impact resistance, chemical resistance, and dimensional predictability. Typical part categories include automotive fluid connectors, pneumatic couplings, cable clips, sensor housings, filter end caps, and industrial brackets.

Published technical data for the PA12-GF23 family place the density in the range 1.22–1.24 g/cm³ according to ISO 1183-1:2019. Tensile modulus is generally reported between 4.5 GPa and 5.0 GPa by ISO 527-1/-2:2012, with tensile strength at break from 80 MPa to 95 MPa. Elongation at break falls to 3–5%, which is characteristic of a short-glass reinforced polyamide with strong orientation-dependent mechanical response. Charpy notched impact strength at 23°C under ISO 179-1/1eA:2010 is typically 8–10 kJ/m². The melting peak measured by differential scanning calorimetry according to ISO 11357-1/-3:2018 is approximately 176–180°C, and the heat deflection temperature under a 1.8 MPa load according to ISO 75-1/-2:2020 is in the region of 115–130°C. These values are class-typical ranges and should be verified against the current Arkema technical datasheet for the exact production lot.

The material designation should not be read as equivalent to a PA12 compound with randomly oriented long glass. In short-glass injection-moulding grades, the measured tensile modulus depends on the degree of fibre orientation produced during cavity filling. Tensile bars gated in the longitudinal direction therefore often exhibit higher stiffness than cross-gated or plaque specimens. The reported 4.5–5.0 GPa modulus should be interpreted as a flow-direction value under standard specimen preparation, not an isotropic bulk property. Similarly, moulded parts with knit lines, abrupt thickness changes, or high shear regions may deviate substantially from datasheet values.

What separates a PA12-GF23 compound from its unfilled PA12 and PA6-GF30 counterparts?

The intermediate glass-fibre content alters the property profile relative to unfilled PA12 and higher-filled PA12 or PA6 grades. Unfilled PA12 typically exhibits a tensile modulus near 1.4–1.6 GPa and elongation at break above 150–200%, whereas the 23% glass reinforcement raises tensile modulus to the 4.5–5.0 GPa range and reduces elongation to 3–5%. The reinforcement also increases creep resistance, reduces thermal expansion, and raises the heat deflection temperature, but it introduces anisotropic shrinkage and lowers resistance to crack propagation under side-gate or weld-line loading. Compared with a 30% glass-filled PA12, the 23% grade produces a lower melt viscosity and generally lower screw torque for the same barrel temperature profile. The lower fibre volume fraction can reduce orientation-induced warpage in flat, multi-cavity moulded parts, although it sacrifices some tensile stiffness and creep resistance.

Against PA6-GF30, the principal difference is the polyamide 12 matrix. Polyamide 12 absorbs significantly less water than polyamide 6. At 23°C and 50% relative humidity, equilibrium moisture uptake for PA12 is often below 0.2%, while PA6 may reach approximately 2.5–3.0% by mass. This difference directly affects part dimensions, glass transition suppression, and electrical properties in humid environments. PA12 also retains higher impact strength at subzero temperatures because its glass transition temperature is lower than that of PA6. The trade-off is that dry-as-moulded PA6-GF30 can offer higher heat deflection temperature and higher tensile strength. A PA6-GF30 grade may have a tensile modulus in the 8–10 GPa range and heat deflection temperature approaching 200°C under 1.8 MPa, but with greater moisture sensitivity and higher density. The PA12-GF23 grade is therefore selected when low moisture uptake, chemical resistance, and dimensional stability in humid automotive or industrial environments outweigh maximum dry stiffness.

Published data for this specific configuration is limited in the open literature, particularly for long-term creep at elevated temperature and fatigue under combined hydrocarbon and thermal load. Designers should not extrapolate short-term ISO tensile values to continuous load-bearing applications without creep-rupture testing according to ISO 899-1:2003 or equivalent internal material specifications. The supplier may provide additional creep and fatigue curves under confidentiality for qualified production programmes.

Before melt processing, the pellets should be dried in a desiccant dryer to a residual moisture target below 0.10%. A common starting condition is 80°C for 4–6 h with a drying-air dew point below −30°C. Insufficient drying can produce surface splay, reduced tensile strength, and viscosity loss due to hydrolysis. The recommended melt-temperature envelope for injection moulding is generally 240–260°C, with mould temperature controlled between 30°C and 60°C to obtain consistent crystallisation and surface appearance. Back pressure in the range 0.3–0.7 MPa and screw speeds of 50–100 min⁻¹ are typical starting points for medium-sized technical parts, although specific settings depend on screw diameter and shot volume. Residence time at melt temperature should be kept below 8–10 min whenever possible, and the shot size should remain between 30% and 70% of barrel capacity to limit thermal history.

On production-scale injection machines, batch-to-batch viscosity shifts can occur with polyamide 12 glass-filled compounds due to moisture variation, regrind content, and lot-to-lot molecular weight differences. Moulders running hot-runner systems should monitor nozzle pressure and fill time rather than relying only on hydraulic pressure. If regrind is reintroduced at weight fractions above 20%, the tensile strength retention and melt viscosity shift should be validated using ISO 527-1/-2:2012 and ISO 1133-1:2022. Glass-fibre length reduction during regrinding can produce lower impact strength even when short-term tensile data appear acceptable.

When four-cavity tooling demands fibre-orientation control below 0.3% shrinkage differential

Controlling differential shrinkage in multi-cavity tools requires attention to gate location, runner balance, and fibre orientation. In semi-crystalline short-glass polyamides, flow-direction shrinkage is lower than cross-flow shrinkage because oriented glass fibres constrain matrix contraction along the fibre axis. Unbalanced filling creates asymmetric orientation patterns that produce bow, twist, and cavity-to-cavity dimensional scatter. The mould shrinkage for a PA12-GF23 compound typically falls within 0.2–0.6% in the flow direction and can be 0.5–0.9% transverse to flow, depending on wall thickness, mould temperature, and packing pressure. These values are not universal constants; they should be measured on cavities representing the final gating scheme according to ISO 294-4:2018.

Weld lines formed downstream of pins, bosses, or multiple gates are weaker in glass-reinforced materials because fibre orientation at the melt front is predominantly perpendicular to the weld plane. For a 23% glass-filled PA12, a weld-line tensile strength retention of 50–70% relative to the unknitted material is common in laboratory plaques, though published data for this specific configuration is limited. Parts requiring pressure-tight behaviour, such as fluid connectors, should avoid weld lines on the sealing bead or thread root. If weld lines cannot be eliminated, increasing mould temperature within the allowed range and moving the weld line into a low-stress region can improve performance.

The lower glass content relative to 30% filled PA12 can be advantageous in thin-wall filling. Melt pressure at the transfer point is generally lower than that required for a higher-fibre grade, and the material can fill ribs and snap-fit features with less hesitation. However, the use of very high injection velocities above 150 mm/s can cause jetting, surface striations, and fibre accumulation at the flow front. Medium injection speeds with profiled transfer from velocity to pressure control are preferred. Weld-line strength and percolation of glass through narrow gates are best assessed by short-shot studies and X-ray computed tomography rather than visual inspection alone.

Hydraulic clamp force requirements depend on projected area and cavity pressure. For moderate technical parts with projected areas up to 300 cm², machines with clamp force in the 120–180 t range are often sufficient at cavity pressures below 50 MPa. Larger parts, deep draw ratios, or hot-runner systems may require more generous clamp margins. The exact clamp force should be calculated from measured cavity-pressure transducers rather than estimated from injection pressure alone.

The grade is suitable for dry-as-moulded assembly operations where dimensional stability, snap-fit flexibility, and resistance to aliphatic hydrocarbons are required. In automotive quick connectors and pneumatic push-in fittings, the glass-reinforced PA12 provides hoop stiffness for sealing elements while retaining the low-temperature impact behaviour expected from polyamide 12. The black colour package is intended for general industrial use. Compliance with the RoHS Directive 2011/65/EU, REACH, and other regional chemical regulations must be confirmed against the current Arkema regulatory statement for the exact grade and production location.

Chemical resistance is matrix-limited. The compound withstands many aliphatic hydrocarbons, mineral oils, greases, dilute alkalis, and salt solutions. Strong acids, concentrated formic acid, chlorinated solvents, and hot aqueous oxidizing media can degrade polyamide 12. The material is not recommended for continuous immersion in hot water or glycol above approximately 90°C under sustained pressure without specific validation, because hydrolysis and plasticisation can reduce molecular weight and creep resistance. Parts exposed to zinc chloride solutions, which can occur in road-de-icing environments, should be evaluated for stress-cracking resistance under service strain. Polyamide 12 generally offers better resistance than PA6 in such environments, but stress concentration at sharp notches or weld lines remains the limiting factor.

Chemical resistance boundaries and moisture-degradation thresholds

In service, moisture content influences both part dimensions and mechanical response. The low equilibrium water uptake of PA12 reduces swelling but does not eliminate it. A hygroscopic expansion coefficient for PA12-GF23 on the order of 0.02–0.04% per 0.1% moisture increase is a reasonable engineering approximation for preliminary tolerance analysis, though anisotropic fibre restraint may produce lower expansion in the flow direction. The exact coefficient should be determined by conditioning moulded plaques at 23°C and 50% relative humidity and measuring dimensional change according to ISO 62:2008 or an internal conditioned-dimension procedure.

Hydrolysis during processing is a separate concern from in-service water exposure. Melt-state moisture above 0.10% accelerates chain scission, causing a measurable loss in melt viscosity and tensile strength. The practical control method is to verify drying-air dew point, drying time, and hopper residence time. A desiccant dryer with insufficient regeneration capacity may fail to maintain the required dew point even when the set-point temperature is correct. In high-humidity plants with ambient relative humidity above 60%, pellets should be conveyed to the machine throat in closed dry-air lines, and open hopper residence time should be limited to less than 30 min. Failure to observe these controls can produce black specking from degraded fines at the screw flights and local glass accumulation at the nozzle.

For applications requiring repeated steam sterilisation or prolonged hot-water contact, a PA12-GF23 grade may be less suitable than high-temperature polyamides such as PPA or PA46. The documented limitations should guide the selection away from alkaline cleaning agents above 80°C, strong organic acids, and phenolic compounds that can plasticise or chemically attack the polyamide matrix. Where the seal or connector is exposed to aggressive diesel exhaust fluid, battery acid mist, or chlorinated cleaning agents, specialised grades with higher hydrolysis resistance or fluoropolymer sealing elements may be required. Published data for this specific configuration is limited, so component validation should incorporate the actual service fluid, temperature, and strain level rather than relying on datasheet chemical-resistance tables.