Arkema Rilsan Fine Powders 6187 BLUE RDP 15-10 FB PA11 is a blue-pigmented thermoplastic polyamide 11 powder supplied as a fine-particle-size fluidized-bed grade. The product designation separates into the Rilsan Fine Powders family, the color-specific 6187 BLUE formulation, the RDP 15-10 FB powder-cut identifier, and the PA11 resin type. PA11 is synthesized from 11-aminoundecanoic acid obtained from castor oil; the repeating unit places an amide group between C10 aliphatic segments, producing a semi-crystalline polymer with a melting range near 183–187 °C and an unfilled density of approximately 1.03–1.05 g/cm³ when measured under ISO 1183-1. Unlike epoxy, polyester, or polyurethane powder coatings, this material contains no crosslinking agent. Film formation occurs by melt coalescence and recrystallization rather than by a curing reaction. The powder is used for metal protection in fluidized-bed dipping and, after line verification, electrostatic spray application; typical target parts include automotive clips, valve springs, consumer goods, and light-alloy components requiring impact resistance and low-friction surfaces.

The PA11 backbone absorbs less water than short-chain nylons. Saturated moisture uptake under ISO 62 is commonly reported near 1.8–2.5 % for unmodified PA11, compared with roughly 9.5 % for PA6 and 8.5 % for PA66 at equilibrium. That lower moisture uptake reduces the swelling and dielectric-property drift observed in humid environments; however, the blue-pigmented grade may not show identical values because the pigment and flow-control additives occupy filler volume. No published certificate of analysis for 6187 BLUE RDP 15-10 FB should be replaced by a generic PA11 datasheet. Grade-specific values for melt volume-flow rate, particle-size distribution, gel time, and adhesion are obtained from Arkema technical documentation.

What separates this blue fluid-bed PA11 powder from PA12, short-chain nylon coatings, and thermoset powders?

PA12 powders typically melt near 176–180 °C and exhibit equilibrium moisture uptake around 1.4–1.6 %. PA11 melts slightly higher, near 183–187 °C, which can provide a wider thermal margin in hot under-hood or steam-sterilized service. Against PA6 or PA66, PA11 offers substantially lower water absorption and better hydrolysis resistance in moist acidic environments because the amide groups are farther apart along the C10 spacer. Against thermoset powder coatings, the PA11 product is a true thermoplastic: it does not pass through a hardener stoichiometry point, and a defective or damaged film can be re-fused. The same property imposes an operational limit. If oven temperature exceeds the onset of thermo-oxidative degradation—often above 230 °C for prolonged dwell—the blue film may yellow or develop surface embrittlement. Published data for this specific blue-pigmented formulation under extended hot-air aging is limited, so production trials are required before use above 200 °C metal temperature.

Compared with polyethylene and polypropylene coating powders, PA11 offers higher heat resistance and lower permeability to aliphatic hydrocarbons, but it is more hygroscopic than polyolefins and must be stored in sealed containers. Compared with solvent-borne nylon coatings, the powder form eliminates solvent handling and permits thicker one-coat films; adhesion still depends on substrate preparation. The blue color is not merely a visual identifier. Pigment loading alters melt flow and gloss; therefore lots should not be blended with clear or black grades without checking melt-flow index under ISO 1133-1 and gel time under ISO 8130-6.

Table 1 lists the standard test matrix used for incoming powder and cured film control. The matrix does not contain grade-specific acceptance limits; acceptance limits are taken from the product certificate of analysis and the coating specification.

On a production fluidized-bed line, the first variable is not powder deposition but substrate thermal mass. Ferrous parts are degreased and grit blasted to a cleanliness of Sa 2½ under ISO 8501-1; light alloys are usually passivated with a chrome-free conversion coating or a silane pre-treatment. The part is then heated in a forced-air oven with a metal-temperature uniformity of ± 10 °C until the part stores enough heat to melt the powder during dwell. For steel sections of 3–6 mm, preheat setpoints commonly range from 260 °C to 350 °C; thin stampings are held at the lower end to avoid edge overheating. The powder is fluidized with dry air at a dew point below 5 °C. A porous plate differential pressure of 80–150 mm H₂O is often sufficient to create a smooth boiling bed; if the bed slumps or spits, the first checks are powder moisture above 0.3 wt% and fines accumulation from reclaimed powder.

Dip dwell is kept between 3 s and 15 s for most first-pass films, followed by draining and passage through a fusion oven at 190–220 °C for 2–10 min depending on part mass. To increase film thickness, the part may be returned to the preheat oven and re-dipped; each re-dip adds a discrete layer, and poor interlayer adhesion occurs if the previous layer is not fully molten during the second hot dip. In line audits, the most common defect is edge pull-back on sharp radii. This is corrected by increasing part mass temperature within the allowed upper limit and by verifying that the blast profile is not less than 25 µm for ferrous parts.

Fluidizing air carries moisture. If the air dew point exceeds 10 °C, the powder surface water content can increase during recycling, causing bed channeling and uneven film thickness. Production lines that run continuous reclaim should monitor differential pressure across the bed plate and reject reclaimed powder that contains visible blue-black specks or non-melting particles. A rotary sieve of 125 µm is used to remove floor sweepings and coarse pigment agglomerates. Batch-to-batch variation in particle-size distribution can arise from classifier shifts; therefore the percentage retained on 63 µm and 125 µm sieves should be checked under ISO 8130-1 before line charging.

When electrostatic spray is used instead of direct immersion

Although the FB suffix indicates fluidized-bed optimization, the powder can be applied with corona-charging guns after hopper fluidization is confirmed. Gun voltage is generally set at 60–80 kV, gun-to-part distance at 150–250 mm, and powder output at 80–150 g/min per gun. The part is not preheated to the same high temperature as in fluid-bed coating; it is sprayed ambient and then heated to 190–220 °C for fusion. This route is used for thinner films in the range 80–150 µm. Reclaimed powder from electrostatic booths should be screened through 125 µm sieves before blending with virgin material at ratios not exceeding 20–30 % unless the line has demonstrated stable particle-size distribution.

Electrostatic application of a fluid-bed grade can be limited by the coarser fraction. If the powder builds up excessively at the fluidizing plate or surges from the powder hopper, a fluidizing air pressure of 0.5–1.5 bar can be applied to the hopper membrane. No additional crosslinker is required; the powder is used as a single-component material. This differentiates it from epoxy-polyester hybrid systems that require stoichiometric hardener mixing and cannot be re-melted after cure.

Film Fusion, Crystallinity Development, and the Role of the C10 Repeat Unit

The fusion of PA11 is not a cure conversion; it is a heat-transfer and crystallization problem. Below 183 °C, the particles may stick but not coalesce into a continuous film; at 190–220 °C, the melt surface tension and viscosity allow particle boundaries to disappear. The cooling step then controls crystallinity. Rapid cooling through the crystallization range produces smaller spherulites and generally higher impact resistance; slow cooling yields greater crystallinity, higher modulus, and lower elongation at break. On production lines, water quench or forced-air cooling is used for thin films, while heavy sections cool slowly and may show more dimensional growth. The C10 spacing in PA11 reduces the hydrogen-bonded planar stacking density relative to PA6; this is one reason for the lower water uptake and more ductile sub-zero response. The pigmented grade may deviate from neutral PA11 because the blue colorant increases melt viscosity and reduces melt flow, so an incoming lot should be checked for melt volume-flow rate under ISO 1133-1 at 235 °C/2.16 kg and for gel time under ISO 8130-6.

Ovens should be calibrated to a metal-temperature profile rather than air temperature only. A thick casting may lag the air temperature by 20–30 °C; if the oven air is set at 220 °C, the part may reach only 190 °C for several minutes, producing an under-fused film with low gloss and poor impact resistance. The target metal temperature is best measured with a thermocouple embedded in a scrap part on the same conveyor. The recrystallization of PA11 begins near 160–165 °C during cooling; water quench or high-velocity air cooling is used to manage crystallinity in films above 200 µm. For films below 100 µm, cooling rate is less critical because the part cools rapidly by conduction.

Where Adhesion Can Fail Despite a Chemically Intact Film

Adhesion failures are rarely caused by the PA11 powder itself. They are typically caused by residual lubricants, oxide scale, or insufficient anchor profile. Degreasing with alkaline cleaners or vapor degreasing is followed by abrasive blasting with chilled iron or alumina grit; for ferrous surfaces, the minimum profile is typically 25 µm, while light alloys require lower-pressure blasting to avoid embedding grit. After blasting, parts are handled with clean gloves and coated within 4 h to avoid flash rust. A phosphate or silane seal can be used where salt-spray resistance under ISO 9227 is specified. The powder should be stored in sealed containers below 30 °C and below 50 % RH; the hopper should be purged with dry air if ambient humidity exceeds 60 % RH. If the powder is exposed to moist air, it may be pre-dried at 60–80 °C for 2–4 h in a tray dryer until moisture is below 0.2 wt%, but grade-specific drying instructions from Arkema take precedence.

The polymer is resistant to aliphatic hydrocarbon immersion at ambient temperature, but strong mineral acids, phenols, and hot polar solvents can degrade or dissolve the film. Immersion testing should follow ISO 175. Because the product is a thermoplastic, it is not suitable for continuous operation above its melting range; sag and loss of adhesion occur if the metal surface reaches 183–187 °C under load. In immersion service, cathodic delamination can occur if the coating is damaged; this failure mode is shared with thermoplastic powders and is evaluated by scribe creep after salt spray under ISO 9227. For high-corrosion-risk parts, a zinc-rich primer or phosphate pre-treatment is used under the PA11 film. The blue powder does not contain zinc; therefore the barrier property of a continuous film is the primary corrosion mechanism. Pinholing is reduced by controlling film thickness above 300–400 µm for aggressive immersion, but the exact minimum depends on part geometry and service medium.

Because PA11 is derived from castor oil, the base polymer may be certified for renewable carbon content under ASTM D6866. The blue pigment and processing aids affect the overall renewable content; a grade-specific certificate rather than a generic PA11 value is required for any renewable-carbon claim. If food-contact status is required, the base PA11 may be referenced under 21 CFR 177.1500 and resinous coatings under 21 CFR 175.300, but the blue pigment and flow additives require grade-specific confirmation from Arkema. REACH documentation is supplied under Regulation (EC) No 1907/2006, and RoHS statements should be obtained for the specific blue formulation before use in consumer articles.

Do not mix the PA11 powder with other polymer powders in the same fluid bed. Low-melting polyethylene powder and thermoset powders will not fuse at the same temperature; contamination by gelled thermoset particles can form hard inclusions in the finished film because the thermoset particles cannot melt at PA11 processing temperatures. Cleaning of hoppers, hoses, and gun nozzles between color changes should be verified by spraying a test panel. In comparative production trials on identical fluid-bed lines, blue grades can show lower initial electrostatic wrap on sharp edges than black or grey grades because of differences in pigment conductivity; this is not a failure of PA11 itself. The correction is to adjust preheat, dipping time, or grounding rather than to raise voltage beyond 80 kV, which may cause back-ionization and orange peel.