Where dimensional flatness of multi-gate fuel flanges survives 1,000 h of Fuel C vapour exposure

In automotive evaporative emission systems, injection-moulded flanges and canister bodies produced from Rilsan BZM 23 G9 are specified for fuel pump retainers, EVAP canister flanges, and fuel filter housings where Fuel C immersion and vapour cycling create combined dimensional and mechanical demands. The compound as supplied contains 23% by weight short glass fibre distributed in a PA11 matrix; the glass fraction reduces mould shrinkage to a published range of 0.2–0.5% in the flow direction and 0.5–1.0% transverse, enabling a 180 mm sealing face to remain within a 0.15 mm flatness tolerance after 1,000 h of cyclic exposure to Fuel C per SAE J1645. Drying before melt processing is mandatory: residual moisture must be below 0.08% by weight after 4–6 h at 80°C in a desiccant dryer with a dew point of -40°C or lower. A barrel profile from 250°C rear to 270°C front and nozzle at 265°C is used, with a mould temperature of 70–80°C; below 60°C mould temperature, the glass-rich skin freezes before pack out and sealing-face flatness shifts upward. Hold pressure is maintained at 50–70 MPa for 6–10 s, followed by 20–30 s cooling. Gate location must place the last filling point away from the sealing land because the weld line formed by opposing glass-flow fronts can retain as little as 50–70% of the unwelded tensile strength under ISO 527-2. Tensile modulus in the conditioned state is typically in the 5,000–6,000 MPa range, while elongation at break remains above 3%, sufficient for snap-fit retainers that must not crack after -40°C impact tests per ISO 16750-4. Regrind addition up to 20 wt% is accepted for non-appearance regions only when the pellet moisture is re-controlled to the same 0.08% threshold and the glass content is verified after re-blending.

Outdoor telemetry boxes, ultrasonic sensor bodies, and electric vehicle charging port housings exploit the low moisture uptake of Rilsan BZM 23 G9 relative to PA66 GF30, because dimensional change after 24 h water immersion per ISO 62 is under 1.0% and equilibrium moisture uptake at 50% RH remains below 1.5% for most wall thicknesses below 3 mm. The 23% glass fibre reinforcement produces a tensile modulus close to 5,500 MPa and a heat deflection temperature of 150–170°C under ISO 75-2/Af, allowing the material to pass short-term peak temperatures near 160°C during selective wave soldering or hot-plate welding of inserts. The melt viscosity of the glass-filled grade demands a reciprocating screw with a 20:1–25:1 L/D ratio and a compression ratio of 2.0:1–2.4:1; back pressure is set at 0.5–1.0 MPa to homogenise fibre distribution without generating enough shear to reduce fibre length below 0.3 mm. For thin-wall connector bodies between 0.8 mm and 1.5 mm, injection velocity is set from 80 mm/s to 120 mm/s, and the mould temperature is held at 80–90°C to ensure fibre wet-out at the surface, which reduces surface glass protrusion and improves comparative tracking index stability under IEC 60112. Because PA11 contains no halogens, the compound normally meets UL 94 HB and RoHS Directive 2011/65/EU threshold requirements, with Lot 4 phthalate restrictions checked on a batch basis. Insulation resistance after 1,000 h at 85°C/85% RH per IEC 60068-2-78 should be verified on the final housing geometry, not on a standard plaque, because surface contamination and mould release can produce leakage paths that are not captured by the material datasheet.

Why does a 23% glass fraction shift the sodium hypochlorite compatibility boundary in pump volutes?

Because dilute sodium hypochlorite residuals attack acetal bushings and generate brittle POM failures in municipal water treatment skids, fixed-displacement diaphragm pump volutes and injector bodies are switched to Rilsan BZM 23 G9 where 0.5–2.0 ppm free chlorine residuals at 20–40°C create oxidative stress. In 10% sodium hypochlorite at 40°C for 28 days under ISO 175, the material typically shows mass change below 0.5% and tensile strength retention above 90%, but concentrated hypochlorite above 12% at temperatures above 50°C is an operational boundary because oxidative surface microcracking and notch sensitivity increase with glass-fibre orientation. The 23% short glass loading raises burst pressure of a 3 mm wall pump volute to approximately 20–25 bar at 23°C, and the fibre network reduces creep under cyclical pressure spikes from 0–10 bar at 60°C. Moulding practice for these parts uses a 20:1 L/D screw with a compression ratio of 2.2:1, screw speed below 150 rpm to limit fibre attrition, and melt temperature from 250°C to 270°C. Fibre length retention above 0.4 mm is the critical quality variable; excessive screw speed or back pressure above 1.5 MPa can shorten number-average fibre length and reduce notched Charpy impact from the typical 10–15 kJ/m² range toward 8 kJ/m² under ISO 179/1eA. The finished valve body and pump casing are often post-conditioned in 80°C water for 24 h before dimensional inspection, because PA11 reaches most of its service moisture growth of 0.1–0.3% within the first 48 h and this step prevents later seal-groove shifting in service. Incompatible service fluids include strong mineral acids at pH below 2 at elevated temperature, phenolic process streams, and concentrated oxidising acids; published data for this specific grade in such environments is limited and end-use qualification is required.

Above the waterline on offshore production platforms, junction-box retention brackets, cable cleats, and bend-stiffener retainer collars are moulded from Rilsan BZM 23 G9 because salt spray, UV, and constant wind pressure impose combined creep and corrosion demands that unfilled PA11 cannot meet. The glass fibre phase raises flexural modulus under ISO 178 to 4,500–5,500 MPa and holds creep under 20 MPa at 60°C to a lower strain than unfilled PA11, while the PA11 matrix resists hydrolysis better than PA6 or PA66 in continuous 3.5% NaCl exposure per ISO 175 at 40°C for 28 days, with tensile strength retention above 85%. Natural unpigmented grades are restricted to short-term outdoor exposure or must be painted because UV radiation under ISO 4892-2 can oxidise a surface layer of 0.03–0.05 mm after 1,000 h; black UV-stabilised variants are preferred for continuous service above 60 months. Thick-section clamps above 6 mm require a reduced cooling rate and a mould temperature of 60–70°C, with pack pressure sustained for 15–20 s and post-mould annealing at 120°C for 2 h to suppress residual stress cracking at -20°C under ISO 179/1eA notched impact testing. The terminal clamp geometry includes integrated nut pockets and is specified to retain 1.5 kN on a steel bolt boss without cracking; the boss diameter must be at least 2.5 times the thread diameter to prevent glass-fibre induced stress concentration at the thread root. Because the material is not flame retardant in this unmodified form, enclosures requiring IEC 60079-7 increased safety for hazardous areas need additional design measures or a flame-retardant variant.

When a compressed air manifold body must maintain a 16 bar seal at 65°C and 80% RH

Industrial pneumatic distribution blocks, push-to-connect fitting bodies, and solenoid mounting manifolds use the compound where compressor oil carryover and high humidity rule out PA66 GF30 due to its greater moisture stiffness loss. Under equilibrium moisture at 50% RH and 23°C, PA11 GF23 retains approximately 90% of dry flexural modulus, whereas PA66 GF30 may retain only 60–70% under comparable conditions according to comparative ISO 527-2 data; this differential is the design basis for using the material in 16 bar circuits at 65°C and 80% RH. The 23% glass fibre loading supplies enough hoop stiffness to limit diametral expansion in a 2.5–4.0 mm wall manifold to below 0.2% under the same pressure-temperature envelope. The tool is sized with 0.3% flow-direction and 0.6% transverse shrink compensation for a typical 4-cavity hot runner system; valve gates are preferred over open hot tips because the glass-filled melt string can freeze and crack at the gate. Melt temperature is set at 265–275°C, mould at 65°C, injection velocity 60–90 mm/s, and screw decompression at 2–3 mm to prevent drool from the hot runner. After moulding, threads are chase-tapped or formed by unscrewing cores with silicone-free lubricant, since external silicone can impair ultrasonic weld strength. Leak tightness of finished manifold bodies is tested at 24 bar for 30 s under air or water, corresponding to 1.5 times the 16 bar nominal working pressure. Service limitations include continuous contact with ester-based compressor oils above 70°C, which can soften the PA11 matrix, and the use of strong alkaline cleaning baths above pH 12 at elevated temperature.

Cyclic flexural loading at -20°C differentiates Rilsan BZM 23 G9 from PA6 GF30 in alpine touring binding toe plates, mountain bike chainring guards, and climbing ascender frames where low-temperature ductility and long-term creep resistance are tested side by side. Notched Charpy impact at -30°C under ISO 179/1eA remains in the 8–12 kJ/m² range, while flexural modulus under ISO 178 reaches 4,500–5,500 MPa, which limits deflection in a 4 mm thick binding plate under 1 kN cyclic load to below 0.2 mm over 5,000 cycles in laboratory fixtures. The semi-ductile failure mode reduces the brittle fracture risk in snap hooks, rope guides, and drone armatures that must pass cold-soak impact after IEC 60068-2-1 storage at -40°C for 4 h. Moulding of structural inserts from this compound is performed with injection velocity of 100–150 mm/s to fill before the glass-rich skin freezes, while melt temperature is capped at 280°C because higher settings accelerate thermal degradation and yellowing in natural grades. A mould temperature of 80°C improves surface finish and shortens gate freeze time by 10–15% but increases transverse post-mould shrinkage by approximately 0.1 percentage point, so dimensional checks on the fully crystallised part are taken after 24 h at 23°C and 50% RH. Overmoulding with unfilled PA11 is feasible because the polymer backbone is identical, but the glass-filled substrate must be preheated to 80°C before the second shot to prevent a weak interface at the glass-rich surface. Published data on overmould bond strength for this specific grade is limited; lap shear specimens should be tested per ISO 527-2 on each tool rebuild.