Evonik VESTAMID® LX9112 is a flexible polyamide 12 (PA12) extrusion and injection-moulding grade formulated to provide lower flexural modulus and higher elongation at break than unplasticized VESTAMID® L-series PA12 compounds. The product is specified under ISO 1874 as a PA12 moulding and extrusion material, with density reported at 1.01 g/cm³ according to ISO 1183-1. Representative supplier data list Shore D hardness in the range of 63–68 when conditioned for 15 s under ISO 868, tensile stress at yield near 20–22 MPa measured by ISO 527-2, and nominal strain at break exceeding 300% at 23 °C. The compound is used in monolayer and multilayer tubing for pneumatic control lines, catheter shafts, cable jackets, and fluid-transfer circuits where polyamide chemical resistance is required but the stiffness of standard PA12 is unacceptable. The plasticizing system reduces the glass-transition-dependent stiffness; the exact plasticizer identity is proprietary and published data for the plasticizer migration rate in this specific grade are limited.

What separates VESTAMID® LX9112 from rigid PA12 and low-hardness polyether-block-amide grades?

The difference is primarily viscoelastic and thermal, not limited to Shore D hardness. Unplasticized PA12 grades such as VESTAMID® L1670 typically exhibit flexural modulus near 1200 MPa (ISO 178) and yield stress above 40 MPa (ISO 527-2). VESTAMID® LX9112 shifts the stress–strain response toward elastomer-like behavior, with flexural modulus typically below 400 MPa and a less pronounced yield point at 23 °C. Compared with polyether-block-amide (PEBA) elastomers of similar Shore D hardness, LX9112 retains the crystalline PA12 melt signature with a melting temperature near 176 °C (ISO 11357-3). That crystalline phase provides higher thermal dimensional stability but lower dynamic flexural fatigue resistance than PEBA. It also differs from PA11 in water uptake: saturated water absorption is approximately 1.0–1.3 wt% (ISO 62), compared with PA11 values above 1.8 wt%, which supports more stable dielectric and dimensional properties in humid environments.

In tube extrusion on a 45 mm single-screw extruder with an L/D 30:1 barrier screw and grooved feed section, the following processing boundaries are applied. The resin is predried at 80 °C to a residual moisture level below 0.10 wt% using a desiccant dryer with a −40 °C dew point; moisture content is verified by Karl Fischer titration according to ISO 15512. Barrel temperatures are profiled from 200 °C at the feed zone to 230 °C at the metering zone, with die-head temperature held at 225–235 °C. Melt pressure at the breaker plate is typically maintained between 120 bar and 180 bar using screen packs of 60/100/60 mesh. A melt pump is recommended for thin-wall tubing with wall thickness below 0.5 mm to reduce surging. Under these conditions, melt temperature measured by immersion thermocouple is 228–238 °C. If melt temperature exceeds 245 °C for more than 15 min, surface roughness and discoloration increase. Published quantitative kinetic data for thermal-oxidative degradation of LX9112 are limited, but lot-specific gel counts rise measurably after extended high-temperature residence. For injection moulding of small connectors and hubs, melt temperature of 235–250 °C and mould temperature of 40–60 °C are used. Holding pressure of 600–900 bar and back pressure of 30–70 bar assist in packing without excessive shear heating. Drying is equally critical because moisture above 0.10 wt% produces splay and hydrolytic degradation during plastication, reducing tensile elongation at break.

Melt-processing parameters and the onset of thermal-oxidative degradation

The melt volume-flow rate is controlled in the range of 8–12 cm³/10 min at 235 °C and 2.16 kg (ISO 1133-1), permitting thin-wall filling without excessive drool in vertical injection units. On production-scale equipment, batch-to-batch variation in melt viscosity is typically observed within ±10% at constant MVR; in free extrusion this can shift tube wall thickness by approximately ±0.03 mm. The processing window is narrower than unplasticized PA12 because the plasticizing system lowers viscosity and can accelerate residence-time-dependent yellowing. Melt temperatures above 250 °C should be limited to less than 10 min of total residence. Purging with polycarbonate, PVC, or acetal is not recommended because incompatible residues can generate acidic species and create black specks. For colour changes, a viscous polyolefin purge followed by a PA12-compatible purge is used to clear the screw and hot runner.

When gamma sterilisation or repeated autoclaving is required in medical tubing

For medical applications requiring terminal sterilisation, the design must account for the plasticized PA12 response to ionizing radiation and moist heat. Gamma irradiation at 25–50 kGy according to ISO 11137 is commonly applied to finished tubing. Unplasticized PA12 generally retains mechanical properties at these doses, but plasticized LX9112 can exhibit slight yellowing and an increase in Shore D hardness of 1–3 points due to oxidation. Repeated autoclaving at 121 °C for 30 min, following ISO 17665-1, may extract low-molecular-weight plasticizer fractions and increase stiffness; after five cycles, some lots show modulus increases of 10–20% relative to non-autoclaved controls. Published data for extended autoclave cycles beyond 20 cycles are limited. Ethylene oxide sterilisation per ISO 11135 is less likely to shift hardness but requires aeration to reduce residual gas levels. Biocompatibility of a specific lot should be confirmed under ISO 10993-5 for cytotoxicity, ISO 10993-10 for irritation and sensitization, and USP <88> Class VI where required. These standards do not certify the raw resin in isolation; they apply to the final device after processing and sterilisation.

Resistance to diesel fuel, hydraulic oil, and zinc chloride solutions is retained because the base polymer is PA12. However, the plasticized LX9112 grade is more susceptible to extraction by polar solvents than unplasticized PA12. Immersion in ethanol or isopropanol at 60 °C for 72 h can remove plasticizer and increase Shore D hardness by 2–5 points; ASTM D543 or ISO 175 test protocols should be used to verify compatibility for specific fluid combinations. Contact with concentrated organic acids or strong oxidizers degrades the polyamide backbone, leading to surface tack and eventual crack initiation. In dynamic flexing applications, environmental stress cracking in the presence of brake fluids or chlorinated solvents may occur at strain levels above 2–3%; parts should be annealed at 120 °C for 2 h to reduce molded-in stress. Continuous service above 90 °C in air is not recommended without validation. Oxidative embrittlement becomes detectable after 1000 h at 120 °C in unplasticized PA12, while plasticized LX9112 may yellow and lose elongation sooner; published data for long-term thermal aging of LX9112 are limited.

Regulatory status and food-contact limitations for plasticized PA12 fluid-handling components

Compliance is a function of the entire article, not only the base resin. VESTAMID® LX9112 can be evaluated under FDA 21 CFR 177.1500 for nylon resins in contact with food, provided the plasticizer and any additives comply with applicable subparts and total extractives fall within the specified end-use limits. For EU market access, Regulation (EU) No 10/2011 requires overall migration testing according to EN 1186 and specific migration testing for the plasticizer; a declaration of compliance is necessarily lot- and conversion-specific. REACH Regulation (EC) No 1907/2006 SVHC screening and RoHS Directive 2011/65/EU Annex II restricted substances are typically addressed by supplier certificate; the manufacturer’s certificate should be reviewed for the current candidate list.

In multilayer catheter coextrusion where VESTAMID® LX9112 is used as an inner or intermediate layer with a PEBA or TPU outer layer, direct adhesion between the plasticized PA12 and the dissimilar elastomer is often insufficient without a tie layer. Coextrusion trials using a 20 mm inner-layer extruder and a 25 mm outer-layer extruder feeding a spiral mandrel die typically require a maleic anhydride-modified tie resin at the interface to achieve peel strengths above 2 N/mm. Without the tie layer, delamination can occur at bend radii below 10 mm. The plasticized PA12 layer should be kept below 245 °C at the die to avoid interfacial viscosity mismatch and layer-thickness variation. Tube quenching in a water bath at 20–30 °C is used to control crystallinity; slower cooling can increase Shore D hardness and reduce flexibility. Post-extrusion conditioning at 50% RH and 23 °C for 48 h stabilizes moisture-dependent dimensions before final assembly.