Arkema Rilsan BUM 30 BLACK is a polyamide 11 injection-moulding compound containing 30% by weight spherical glass bead filler. Under ISO 1043-1 the material designation is PA11-GB30. The base polymer is synthesised from 11-aminoundecanoic acid rather than the caprolactam route used for PA6, which contributes to lower equilibrium moisture absorption than PA6 or PA66 and a longer methylene sequence between amide linkages. The black colouration is added during compounding. Published experimental data for this exact black glass bead configuration is limited; mechanical and rheological values should be taken from the current manufacturer datasheet and confirmed on production tooling.

What Distinguishes Spherical Glass Bead Filler from Milled Glass Fibre or Mineral Reinforcement in PA11?

At equal nominal 30% loading, spherical glass beads create a different stress-transfer and shrinkage response than high-aspect-ratio fibres. Fibre-reinforced PA11 grades show pronounced anisotropy: tensile modulus measured according to ISO 527-2 is higher parallel to fibre orientation than perpendicular to it, and mould shrinkage measured on ISO 294-4 plaques can differ by more than 0.3% between parallel and transverse directions. Glass bead filled PA11 reduces the parallel-transverse differential because the beads have no preferred orientation under shear flow; local packing varies with gate location and fountain flow but without the mechanical orientation of fibres. The trade-off appears in tensile strength and notched impact. Fibre grades retain higher tensile strength and higher notched Charpy impact under ISO 179-1/1eA because fibres bridge crack planes. Bead-filled grades are selected when dimensional tolerance and low warpage are the primary design requirements and the load is not impact-critical.

At the same time, the 30% by weight glass bead loading corresponds to roughly 14–15% by volume when the glass bead density is taken as 2.5 g/cm³ and the PA11 matrix density as 1.04 g/cm³. The volumetric filler fraction matters in rheology because spherical glass beads increase melt viscosity less than high-aspect-ratio fibres of the same weight loading; the lower aspect ratio reduces the particle-particle network strength under shear. In compounding, the glass beads are incorporated by twin-screw dispersion rather than distribution-only mixing. This gives the final injection-moulding grade a uniform bead concentration across pellets; segregation during transport is relatively low compared with blends of pellets and chopped glass fibre but can increase if excessive fines are generated. On injection-moulding machines with general-purpose screws, the low aspect ratio permits higher screw recovery speeds than glass fibre grades without significant filler fracture; however, the glass beads are not fully non-abrasive and should be treated as a mild abrasive in maintenance planning. Incoming lots should be checked for ash content according to ISO 3451-1 and melt volume-flow rate according to ISO 1133-1 at 235°C/2.16 kg to control batch-to-batch variation before production runs.

Pre-drying is mandatory on desiccant dryers with a dew point of −30°C or lower. The glass bead filler does not eliminate moisture absorption; PA11 is hygroscopic and residual moisture above 0.10% causes surface splay and hydrolytic molecular-weight reduction. Drying at 80–90°C for 4–6 hours is typical, with moisture content verified by Karl Fischer titration or a calibrated loss-on-drying analyser. After drying, exposure to relative humidity above 60% can re-condition open material within 20–30 minutes; hopper dryer residence should be managed accordingly. Injection units with L/D ratios of 20:1 to 24:1 and compression ratios of 2.5:1 to 3.0:1 are adequate. The spherical filler causes less screw and barrel abrasion than 30% glass fibre, but check rings and non-return valves still require hardened or bimetallic construction for campaigns beyond 100,000 cycles. Barrel temperatures are normally profiled from 230°C at the feed zone to 260–280°C at the nozzle; melt residence time above 300°C should be avoided because amide degradation and black colour shift can occur. Mould temperature affects crystallisation kinetics and out-of-mould shrinkage. 40–60°C is common for cycle-time control; 70–80°C improves dimensional stability in thicker sections. Holding pressure of 40–60% of injection pressure, correct gate freeze time, and medium screw recovery speed reduce jetting and uneven bead distribution. On production-scale machines with clamp force between 600 kN and 1200 kN, glass bead filled PA11 flows through pin gates with lower pressure drop than glass fibre PA11, but low injection speed or melt temperature below 240°C can produce surface flow marks.

Dimensional Stability, Moisture Conditioning, and Chemical Resistance

Conditioned at 23°C and 50% relative humidity, PA11 absorbs less water than PA6 and PA66. The glass bead fraction further reduces linear hygroscopic expansion because the inorganic phase does not swell. Dimensional change after conditioning must be evaluated using ISO 62 on finished parts, not resin-only coupons, because wall thickness and gate position control local moisture uptake. A tolerance below ±0.05 mm on a 50 mm cover can still shift after moisture equilibration; the bead-filled grade reduces the shift relative to unfilled PA11 but does not eliminate it. Chemical resistance follows the PA11 matrix: the grade generally withstands aliphatic hydrocarbons, fuels, and many oils, while polar solvents, strong acids, and aqueous glycol mixtures can plasticise or attack the surface. Continuous under-hood exposure above 120°C may reduce mechanical properties; published data for this specific black configuration is limited.

Tool design for glass bead filled PA11 must account for the difference between in-plane shrinkage and thickness shrinkage. In unfilled PA11, shrinkage is often higher in the thickness direction than in the flow direction because of crystallisation and packing; glass bead reduces this differential but does not make it zero. Cavity dimensions should be corrected using actual measured shrinkage from a preliminary tool or a similar geometry. Gate size, runner diameter, and venting should follow PA11 injection guidelines: unidirectional flow with generous end-of-fill vent channels of 0.01–0.02 mm depth prevents gas trapping. Direct gates should be avoided for large flat parts because the gate area may create a dense bead-depleted skin; fan gates or tab gates give more uniform bead distribution across the melt front. On production-scale equipment, parts moulded with insufficient holding pressure show higher sink opposite ribs and greater differential shrinkage between ribs and plain walls.

Field experience on production-scale injection-moulding lines shows three recurring defects when this class of material is run outside its recommended envelope: moisture-induced splay, gate blush from excessive fill speed through small edge gates, and post-mould dimensional drift when parts are packaged before full crystallisation. Splay is resolved by confirming residual moisture below 0.10% and by checking that the machine feed throat is not open to humid air. Gate blush is reduced by lowering injection speed until the flow front remains uniform or by increasing gate diameter; glass bead filled PA11 is less shear-thinning than unfilled PA11, so gate shear stress must be controlled. Post-mould drift is managed by fixture cooling or by delaying final dimensional inspection for 24–48 hours after moulding.

Glass bead filled PA11 is specified for injection-moulded housings, clips, connectors, and thin-walled covers where fibre orientation cannot be accepted. In electric and electronic connectors, the lower moisture uptake reduces changes in dielectric and dimensional properties after humid exposure; comparative CTI or surface resistivity values must be obtained from the manufacturer because carbon black pigmentation can alter insulating character. Components requiring tight snap-fit dimensions should use shrinkage measured on the actual cavity geometry, because ISO 294-4 plaques do not capture rib-induced sink or gate-area packing variation. The material is not optimised for high-speed impact at sub-zero temperatures; if a part is exposed to low-temperature impact, an impact-modified PA11 or a fibre-reinforced, elastomer-toughened PA11 should be evaluated. The use of regrind should be limited to 20–30% by weight; multiple heat histories increase acid end-group concentration and shift crystallinity, which can affect mould shrinkage and warpage.

When Long Flow Paths and Thin Walls Are Required Without Adding High Aromatic Heat Stabilisers

Thin-wall moulding with wall thickness below 1.0 mm can be performed when the melt temperature is kept in the upper processing range and the mould is filled with high injection speed. The spherical filler produces a lower viscosity increase than fibrous reinforcement, which assists long flow paths. Spiral flow length tests at 2 mm wall thickness and 250°C melt temperature provide a comparative tool design ranking; published data for this specific black grade is limited. The black version may exhibit slightly higher melt viscosity than natural versions because carbon black masterbatch affects melt elasticity and thermal homogeneity. Gate size, runner diameter, and venting should follow PA11 injection guidelines: unidirectional flow with generous end-of-fill vent channels of 0.01–0.02 mm depth prevents gas trapping. In hot-runner systems, thermal uniformity across the manifold is critical because residence time in hot drops can produce black streaks or filler segregation.

Glass Bead Filled PA11 Sits Between Unfilled PA11 and Glass Fibre-Reinforced Grades in Stiffness and Warpage Control

Unfilled PA11 provides high elongation and low-temperature ductility but exhibits higher mould shrinkage and lower flexural modulus. A 30% glass fibre reinforced PA11 moves stiffness and tensile strength upward but introduces anisotropic warpage and a rougher surface. The glass bead grade occupies an intermediate position: flexural modulus is raised relative to unfilled PA11, but the absence of fibre orientation reduces part warpage. For maximum dimensional repeatability in all directions, the bead-filled grade is often the baseline; if the part subsequently fails notched impact tests, a shift to fibre reinforcement or impact modification is made. This compromise should be quantified on the actual geometry using ISO 178 flexural tests and ISO 179-1/1eA notched Charpy values from the material datasheet.

Compared with PA12 glass bead filled grades, PA11 provides a higher melting point and generally better stiffness at elevated temperature, while PA12 offers lower moisture absorption and better low-temperature flexibility. Compared with PA6 or PA66 bead-filled grades, PA11 absorbs less moisture, so its conditioned mechanical properties and dimensions remain closer to dry-moulded values. This is relevant in parts that are assembled dry but exposed to ambient humidity in service. The glass bead filler in all these resins is not a reinforcing fibre, so the design should not rely on high tensile strength; cylindrical or spherical filler improves compressive load distribution and reduces warpage but does not provide the crack-bridging mechanism of fibres.

Rilsan BUM 30 BLACK is supplied black but UV resistance is not automatically equivalent to a specifically UV-stabilised grade. Carbon black can improve light screening relative to natural PA11 if the dispersion is fine and the loading is sufficient, but it does not replace a UV stabiliser package. For outdoor use, the relevant accelerated weathering data should be requested according to ISO 4892-2 or ASTM G154. Freeze-thaw and thermal cycling can also induce microcracks at the bead-matrix interface; parts should be thermally cycled between −40°C and 80°C with dimensional checks before production release.

The black pigmentation may increase surface conductivity compared with natural PA11 if a conductive carbon black is used, but standard black masterbatch does not imply static-dissipative performance. Surface resistivity should be measured to IEC 62631-3-2 or ASTM D257 if the part is used in an environment where electrostatic discharge is a concern. The glass bead filler can also influence comparative tracking index if the filler is not coated; the manufacturer should supply the relevant CTI value according to IEC 60112 for connector applications.

Food-contact use of this grade is not assumed from the product name. The supplier should be asked for EU Regulation (EU) No 10/2011 migration documentation or FDA 21 CFR 177.1500 compliance for the specific black glass bead formulation. Glass bead surface coatings and black pigments may be subject to separate positive-list requirements in food-contact or medical devices; raw material reviews must include these minor constituents. For medical devices, ISO 10993 biological evaluation and the relevant biocompatibility data set are not automatically covered by industrial PA11 data.

Lot-to-lot consistency is monitored by melt volume-flow rate according to ISO 1133-1 at 235°C/2.16 kg and ash content according to ISO 3451-1. The glass bead size distribution influences surface finish and mechanical property variation; incoming lots should be compared against the supplier certificate of analysis.