Evonik VESTAMID® LX9043 NC is a natural-colour, plasticizer-free polyamide 12 (PA12) extrusion grade supplied as cylindrical pellets. The polymer is produced from laurolactam by hydrolytic ring-opening polymerisation; the resulting PA12 backbone places eleven methylene units between amide linkages, which lowers amide density and equilibrium water affinity relative to PA6 or PA66. The grade is classified as a low-viscosity, semi-flexible extrusion resin within the VESTAMID L series. Because no external plasticizer is added, flexibility and low-temperature impact response are derived from the PA12 backbone and controlled crystallisation rather than from migratory benzenesulfonamide or phthalate-type plasticisers. Dry-as-molded property data published by the manufacturer include density 1.01 g/cm³ (ISO 1183), tensile modulus 1.5–1.7 GPa (ISO 527-1/-2), tensile stress at yield 42–45 MPa, nominal strain at break >200%, and Charpy notched impact strength at 23 °C reported as no break (ISO 179/1eA). Flexural modulus is 1.2–1.5 GPa (ISO 178), Shore D hardness is 70–72 (ISO 868), Vicat softening temperature VST/A/50 is 165–170 °C (ISO 306), and the crystalline melting peak is 174–178 °C (ISO 3146). Melt volume-flow rate at 235 °C and 5 kg load is 6–10 cm³/10 min (ISO 1133-1:2022). Water absorption at saturation in 23 °C water is 1.5–1.8 wt% (ISO 62), compared with 9–10 wt% for PA6 at equilibrium. The glass transition temperature is typically 45–55 °C by dynamic mechanical analysis at 1 Hz.

How Does the Grade Compare with Plasticized PA12 and Unmodified PA12 Extrusion Resins?

Differentiation from plasticized PA12 compounds is most visible after thermal aging. Plasticized compounds containing 8–15 wt% benzenesulfonamide plasticiser lose mass and increase in stiffness after 1,000 h at 100 °C, whereas LX9043 NC retains tensile elongation above 150% and shows no additive migration to die lips, vacuum-tank water, or downstream fitting surfaces. Compared with unmodified VESTAMID L1670, LX9043 NC has lower melt viscosity and higher notched impact at −30 °C, at the expense of a slightly lower continuous-use temperature under load. The following table compiles representative comparative values; lot-to-lot variation and conditioning state must be verified for each production tool.

Compared with PA11, PA12 contains one additional methylene unit per repeat unit, reducing amide density further at comparable crystallinity; PA11 may offer higher renewable-carbon content in some supply chains. Compared with PA6 and PA66, PA12 gives lower equilibrium moisture uptake and better retention of impact below 0 °C, but lower tensile strength and lower heat deflection temperature under load. Melting points of PA6 and PA66 are 220–225 °C and 260–265 °C respectively; PA12 processes at 220–230 °C, reducing thermal degradation risk and energy input in thin-wall profile extrusion.

Extrusion Melt Rheology and Barrel Temperature Control with Desiccant Drying

Residual moisture is the controlling variable in thin-wall extrusion because hydrolysis of the amide linkage proceeds rapidly above 200 °C. The recommended moisture content before processing is below 0.1 wt%. At 0.15 wt%, melt-pressure variation and surface pinholes are observed on 8 mm outer diameter tubing with 1 mm wall thickness. A desiccant-hopper dryer set to 80–85 °C with inlet-air dew point below −30 °C and residence time of 4–6 h is adequate for sealed bags. Dried pellets are conveyed with dry-air purge to the extruder throat. On a 30:1 L/D single-screw extruder of 45 mm diameter with a three-zone barrier screw and compression ratio 2.5:1–3.0:1, a representative barrel profile from feed to metering is 200 °C, 220 °C, 230 °C, 225 °C, with head and die at 220–230 °C. Melt temperature measured by needle thermocouple should be 225–235 °C and must not exceed 240 °C. Residence time above 230 °C is kept below 10 min to limit thermo-oxidative chain scission, which reduces burst strength and promotes yellowing. A screen pack of 40/60/80 mesh is placed before the breaker plate. At shear rates from 100 s^-1 to 1,000 s^-1, the melt is pseudoplastic, permitting stable wall-thickness control with vacuum sizing. The water-bath temperature is maintained at 40–60 °C to avoid quench-induced amorphous orientation that later crystallises and shrinks.

Air-brake and pneumatic-control tubing constitute a primary application. The grade is evaluated against SAE J844 for non-metallic air brake tubing and DIN 74324 for polyamide tubing in compressed-air braking systems. Low moisture uptake stabilises tube inner diameter at 23 °C and 50% RH; after 168 h conditioning, moisture content is 0.5–0.8 wt%, which alters flexural modulus by less than 15% relative to dry-as-molded material. Burst-pressure retention after heat aging at 100 °C for 1,000 h is a critical validation point. Plasticizer-free construction removes additive migration that can leave internal surface films and reduce fitting retentive force. In multi-layer fuel-vapour lines, LX9043 NC may serve as a tie or outer layer where resistance to zinc chloride and road salt is required. On production lines, dimensional tolerance of ±0.05 mm on outer diameter is maintained when vacuum calibration is set between −0.02 MPa and −0.04 MPa and haul-off speed is controlled to ±0.5%.

Chemical resistance follows aliphatic polyamide behaviour: the grade is resistant to greases, oils, fuels, zinc chloride solutions, and many solvents. It is not recommended for strong mineral acids above 10% concentration, phenols, or formic acid at elevated processing temperatures. Stress-cracking resistance in zinc chloride solution is evaluated by ISO 22088-3 or OEM-specific bent-strip methods. For fuel-contact service, permeation must be measured according to SAE J1737 or equivalent test method.

When Thin-Wall Tube Extrusion Replaces Plasticized PA12 in Automotive Pneumatic Lines

Substitution of a plasticised PA12 with LX9043 NC requires process and design adjustments. Because the plasticizer-free grade has higher flexural modulus, the minimum bend radius in convoluted or spiral-wrap tube should be increased by 10–15% compared with a 12 wt% plasticised compound to prevent stress whitening at the outer bend surface. Low-temperature notched Charpy impact at −40 °C (ISO 179/1eA) is typically 8–10 kJ/m² lower than that of a heavily plasticised PA12, so wall thickness cannot be reduced without repeating OEM impact tests. Production experience on a 45 mm grooved-feed single-screw extruder with 30:1 L/D shows that screw torque decreases 8–12% when barrel temperature increases from 210 °C to 230 °C; melt-pressure instability appears if screw speed changes faster than 5 rpm/min because pellet feed and melt compressibility interact with low melt viscosity. Die-lip temperature uniformity is more critical for plasticizer-free grades: circumferential lip temperature differences greater than 3 °C generate visible wall-thickness banding in thin-wall tube. When downstream printing or marking is used, adhesion is influenced by the absence of surface plasticizer; corona treatment at 2–4 kW and 60–80 W·min/m² is required to raise dyne level above 40 mN/m (ISO 8296). Die swell must be characterised on target tooling because plasticizer-free and plasticised grades differ in melt elasticity; no universal correction factor is available. Published data for specific line configurations is limited, so processor validation on the intended tooling remains necessary.