In heavy-duty vehicle air braking systems, extrusion of Rilsan BESNO 400 TL NL into non-reinforced thermoplastic tubing is qualified by dimensional stability after heat ageing and by burst pressure retention after exposure to zinc chloride road brine. The governing specifications for this application are SAE J844:2019 and ISO 7628-1:2010; the latter low-temperature impact procedure at -40 °C and burst-pressure retention after 72 h at 100 °C determine whether a given extrusion lot can be released. A production compound is built at 100 phr Rilsan BESNO 400 TL NL, with 0.3–0.5 phr hindered phenolic antioxidant masterbatch, 0.1–0.25 phr external lubricant, and 0.05–0.15 phr fluoropolymer process aid. When the finished line must meet ISO 7628-1:2010 impact resistance at -40 °C, plasticizer addition is held at 6–10 phr; increasing the plasticizer fraction above 10 phr lowers the 60 °C burst pressure and increases extractables in ASTM D543:2021 immersion testing. Extrusion on a single-screw extruder with 30:1 L/D, 3:1 compression ratio, and barrier mixing section requires pre-drying to ≤0.08 wt% moisture at 80 °C for 4–6 h using -40 °C dew-point air. Melt temperature at the die is controlled at 235–245 °C; die land length is maintained at 8–12 times the annular gap to limit draw-down orientation. Vacuum calibration at 0.3–0.6 bar sets outside diameter, and ultrasonic wall-thickness scanning controls ovality to ≤0.15 mm. If melt temperature falls below 225 °C, screw torque rises and the onset of melt fracture at the die exit is observed; above 255 °C, the resin yellows and molecular weight loss accelerates. The terminal article is smooth or spirally marked air brake tube with outside diameter 6–16 mm and wall thickness 1.0–2.0 mm, supplied as straight lengths or coils for commercial vehicle pneumatic circuits.

What Limits PA11 Pressure Sheath Extrusion in Unbonded Flexible Risers?

The pressure sheath layer in unbonded flexible risers converts Rilsan BESNO 400 TL NL into a continuous annular barrier between produced fluids and steel armour wires. Qualification of this layer follows API Spec 17J:2014, ISO 13628-2:2023, and API 17TR2:2021, with tensile, elongation, and creep measurements after ageing in simulated formation water and after gas decompression cycles. A base compound is charged at 100 phr BESNO 400 TL NL, with 0.4–0.8 phr primary antioxidant, 0.2–0.4 phr secondary antioxidant, 0.05–0.15 phr processing aid, and 0.0–5.0 phr plasticizer. The plasticizer ceiling is set because API 17TR2:2021 methanol ageing extracts plasticizer and reduces creep resistance; when the riser design temperature exceeds 65 °C, the sheath is extruded without plasticizer, and when low-temperature bending below -20 °C governs, plasticizer is limited to 3–5 phr. Sheath extrusion uses a 90–150 mm single-screw extruder with 30:1–36:1 L/D, grooved feed section cooled to 40–60 °C, melt pump, and 200–400 mesh screen pack. The die is a straight annular crosshead sized for 50–300 mm internal diameter. Melt temperature is held at 230–255 °C; draw-down ratio is kept below 1.2 to prevent frozen-in orientation. Cooling in the vacuum tank uses water at 60–75 °C to slow crystallization and reduce internal stress; for wall thickness above 6 mm, heat extraction is limited by the thermal conductivity of PA11 at approximately 0.22 W/(m·K), so tank residence time is extended and wall temperature is monitored by contact thermocouple. A spark test at 20–30 kV locates pinholes, and ultrasonic wall-thickness scanning enforces ±0.2 mm wall tolerance.

The terminal product is an extruded PA11 pressure sheath integrated inside an unbonded flexible riser, with inside diameter from 50 mm to 300 mm and wall thickness from 4 mm to 10 mm, for offshore oil and gas flowlines and injection risers. In configurations above 10 mm wall or above 260 mm inside diameter, published processing data for this specific medium-viscosity grade are limited, and a high-viscosity PA11 or a coextruded tie-layer structure is usually evaluated.

In heavy-duty diesel aftertreatment circuits carrying 32.5 wt% aqueous urea solution, the extruded line must resist freeze-thaw expansion at -11 °C, urea crystal abrasion, and ammonia vapour migration at 80 °C. The governing requirements are ISO 22241-1:2019 for AUS 32 quality and ISO 22241-2:2019 for material compatibility; suppliers also test burst retention after 500 h immersion in circulating 32.5 wt% urea at 70 °C. A production compound is set at 100 phr Rilsan BESNO 400 TL NL, with 0.3–0.6 phr hindered phenol antioxidant, 0–4 phr plasticizer, and 2–3 phr carbon black masterbatch when ultraviolet opacity is required. Plasticizer above 4 phr is avoided because it raises urea extractables and lowers weld-line strength in injection-molded connectors. Tube extrusion on a 30:1 L/D single-screw extruder with 3:1 compression screw is conducted after pre-drying at 80 °C for 4–6 h to ≤0.08 wt% moisture; melt temperature is 230–245 °C. Double vacuum calibration, with first tank pressure 0.4 bar and second tank 0.6 bar, controls ovality below 0.10 mm for coupling retention. Where thermal protection is required, the line is corrugated in-line at 60–80 °C surface temperature. Jointing is performed by ultrasonic welding of PA11 fittings rather than adhesive bonding; assembled lines are burst tested at ≥5 bar. The terminal article is smooth or corrugated DEF/SCR feed and return line with outside diameter 8–14 mm and wall thickness 1.0–1.6 mm, used in Euro VI, EPA 2010, and China VI heavy-duty trucks. Continuous external exposure to concentrated 30% hydrochloric acid or strong phenolic solvents is outside the acceptable service envelope; such conditions require protective jacketing or grade substitution.

Halogen-Free Cable Sheathing in Rail Transit and Oilfield Instrumentation

Cable constructions for rail transit and oilfield instrumentation use Rilsan BESNO 400 TL NL as a halogen-free outer sheath where fire gas acidity, low smoke density, and abrasion resistance are specified. Compliance is verified under IEC 60754-1:2011, IEC 60754-2:2011, and EN 45545-2:2020; halogen acid gas evolution is controlled to the standard limit, and smoke acidity is measured as conductivity below the threshold of 10.0 µS/mm. The sheathing compound is charged at 100 phr resin, with 0.2–0.5 phr hindered phenolic antioxidant, 0.1–0.2 phr copper deactivator for contact with current-carrying conductors, and 0.05–0.1 phr external lubricant; no halogen-containing flame retardant is used. Extrusion is performed through a crosshead die on a 24:1–30:1 L/D single-screw extruder with a 3:1 compression ratio barrier screw. Wire preheat is set to 60–90 °C, melt temperature to 240–250 °C, and screen pack to 120/200/120 mesh. Pressure tooling is preferred over semi-pressure tooling to eliminate air entrapment between the jacket and the cable core. Cooling water is maintained at 30–50 °C to avoid surface quench-induced voids. On-line spark testing uses 5–15 kV depending on jacket wall thickness. The terminal product is a halogen-free PA11 jacket over power, control, signal, or instrumentation cable, with outside diameter 2–25 mm, intended for rolling stock, trackside, and downhole oilfield service. Continuous conductor temperature above 105 °C is not recommended because long-term thermal ageing at higher temperatures reduces elongation at break below the minimum required by EN 45545-2:2020.

When Injection Moulding of Bio-Based Footwear Components Demands Dimensional Repeatability

Moulding of high-stiffness, low-density footwear plates from BESNO 400 TL NL requires close control of crystallinity because part flatness after ejection is governed by the cooling-rate differential between the cavity surface and the core. Under REACH Regulation EC 1907/2006 and RoHS Directive 2011/65/EU, the material is free of intentionally added halogenated flame retardants and heavy-metal stabilizers. Flexural modulus is measured according to ISO 178:2019 at 23 °C, and moisture-conditioned impact strength is measured according to ISO 179-1:2020. The compound is charged at 100 phr resin, 0.2–0.4 phr internal release agent, 0.3–0.5 phr heat stabilizer, and 0.05–0.15 phr nucleating agent; glass fibre is not used because the target part requires high elongation at break and low density. Pre-drying at 80 °C for 4–6 h to ≤0.08 wt% moisture is mandatory. Injection moulding is carried out on a hydraulic or electric machine with 40–100 t clamp force, screw diameter 25–45 mm, melt temperature 230–250 °C, mould temperature 40–80 °C, injection pressure 800–1200 bar, holding pressure 400–600 bar, and back pressure 5–15 bar. Mould filling uses a two-stage profile: slow initial advance at 15–25 mm/s to displace air, then fast fill at 60–120 mm/s to prevent premature freeze-off. Holding time is set to gate seal, normally 8–20 s depending on wall thickness 2–6 mm. Warpage is controlled below 0.5 mm across a 150 mm part by maintaining mould temperature variation across the cavity at ≤5 °C. The terminal articles are rigid plates and shanks for football boots, ski touring bindings, and snowboard binding baseplates. Continuous load-bearing service above 70 °C is not recommended because creep deformation exceeds 0.5% after 1000 h at 10 MPa in published short-term data; for such loads, glass-filled PA11 grades are evaluated.