RTP Company RTP 287E Amorphous Nylon (Am. PA) Carbon Fiber 40% is a carbon-fiber-reinforced amorphous polyamide compound supplied by RTP Company for injection molding and structural part production. The product code identifies a formulation in which a non-crystalline polyamide matrix is reinforced with 40% by weight carbon fiber. Unlike semicrystalline polyamide 66 or polyamide 6, the amorphous matrix does not exhibit a sharp crystalline melting point, which changes its mold shrinkage, moisture response, thermal softening behavior, and dimensional stability in precision parts. The grade is supplied as free-flowing pellets and is intended for stiffness-driven applications requiring low warpage, controlled thermal expansion, and static-dissipative or conductive characteristics. Because the supplier does not disclose the exact aromatic comonomer ratio of the amorphous polyamide matrix, material selection should be based on the manufacturer’s current technical datasheet and lot-specific certification rather than on a single generic property set.

For design screening, the following representative property values are drawn from published RTP Company datasheet information for this product. The data are generated on injection-molded specimens in the dry-as-molded condition at 23°C and 50% relative humidity unless otherwise noted. They should not be treated as simultaneous lot minima because fiber orientation, moisture content, and processing parameters influence final part performance.

The carbon fiber phase dominates the tensile and flexural response. At 40% loading, the compound is intended for structural housings, brackets, rotors, and precision support components rather than high-elongation snap-fit designs. Tensile strain at break is typically below 2%, and the failure mode is quasi-brittle with limited necking. Stress concentrations at sharp internal corners, weld lines, gate scars, and ejector marks therefore control ultimate part strength more than nominal tensile strength. If design codes require ISO-based values, tensile properties should be re-evaluated according to ISO 527-2:2012 on specimens cut from production-representative plaques, because specimen geometry and gating alter fiber orientation and failure strain.

Carbon fiber reinforcement also reduces the coefficient of linear thermal expansion and improves dimensional stability relative to glass-fiber and mineral-filled semicrystalline nylons. However, orientation effects remain significant. In the flow direction, the coefficient of linear thermal expansion typically falls in the range of 1.0–2.5 × 10⁻⁵ K⁻¹ when measured by ISO 11359-2:2021 on a plaque, while the transverse direction may show values two to three times higher depending on gate location and wall thickness. Mold shrinkage for this amorphous carbon-fiber-filled grade is lower and more isotropic than for a comparable 40% carbon-fiber-filled semicrystalline PA 66. For close-tolerance components, published supplier data indicates mold shrinkage in the range of 0.05–0.10% in both flow and cross-flow directions under controlled molding conditions, but actual values depend on packing pressure, mold temperature, gate freeze time, and part thickness.

What Drying and Injection Molding Parameters Should Be Specified for RTP 287E?

Pre-drying is mandatory before melt processing because the amorphous polyamide matrix is hygroscopic and the carbon fiber sizing can retain surface moisture. A closed-loop dehumidifying hopper dryer with a supply-air dew point of -40°C or lower is recommended. Drying at 80°C for 4–6 h is typically sufficient for sealed fresh pellets to reduce moisture content below 0.05% by weight. If regrind is stored in humid plant air or if the dryer is not equipped with a dew-point monitor, longer residence time or lower regrind ratios may be required. Reclaim levels above 30% by weight should be evaluated for fiber-length retention, notched Izod impact retention, and surface resistivity stability before production release because carbon-fiber-filled materials lose toughness and conductivity control when fiber length is reduced.

For injection molding, barrel temperature profiles should produce a melt temperature of 249–293°C. Rear zone setpoints are commonly 249–271°C, middle and front zones 271–293°C, and the nozzle 277–293°C. Mold temperature should be held between 65°C and 95°C. Higher mold temperatures improve weld-line strength, surface conductivity, and dimensional stability but lengthen cycle time. Back pressure in the range of 0.3–0.7 MPa assists homogenization; excessive back pressure accelerates fiber breakage and increases melt temperature. Screw speed should be limited to 50–100 rpm for screw diameters above 40 mm on production machines to control shear heating and preserve fiber length.

Carbon fiber is abrasive. Production equipment should use bimetallic barrels, screws with high-wear coatings in the metering zone, hardened check rings, and hardened nozzle tips. A screw compression ratio of 2.0–2.4:1 with a low-shear mixing tip is preferable. General-purpose screws with compression ratios above 2.5:1 may shorten fiber length, reduce tensile modulus, and increase variation in surface resistivity. Hot-runner systems require externally heated manifolds with smooth transitions and minimal dead spots because carbon-filled amorphous polyamide can stagnate and degrade in unheated pockets. At scheduled shutdown, the machine should be purged with a compatible amorphous nylon or a stiffening purge compound to prevent conductive residue from accumulating in the check ring and screw tip.

Because the matrix is amorphous, differential scanning calorimetry does not provide a sharp melting endotherm for calibration. Lot-to-lot melt consistency should be monitored by capillary rheometry according to ISO 11443:2021 or by injection-pressure variation at a fixed fill time. A variation in peak injection pressure above 10% from the established process window may indicate moisture re-uptake, incorrect barrel profile, or a change in filler dispersion and should trigger a halt for material inspection.

Experience on production-scale twin-screw compounding lines with L/D ratios of 40:1 indicates that carbon fiber length retention is strongly affected by side-stuffing location and screw design. High-intensity kneading blocks can reduce mean fiber length below 75 μm, while distributive mixing elements may retain mean fiber length above 150 μm. Since fiber length influences tensile modulus, notched Izod impact, and electrical conductivity, incoming lots should not be approved solely on pellet color or moisture content; a molded specimen comparison against the qualified property set is required when a new lot is introduced.

Moisture Uptake, Mold Shrinkage, and Thermal Response in Humid Service

Moisture absorption changes both dimensional and electrical behavior. After 24 h immersion in 23°C water, water absorption for RTP 287E is typically below 0.15%. But long-term humid aging at 85°C and 85% relative humidity produces higher equilibrium uptake and can depress the glass transition temperature of the amorphous matrix. Because the carbon fiber phase does not absorb water, dimensional change is anisotropic and is driven primarily by matrix swelling. For precision parts, a humidity conditioning step may be required before final inspection; otherwise, post-mold moisture uptake can produce dimensional growth and relaxation of molded-in stress.

Mold shrinkage is lower than that of unfilled or mineral-filled semicrystalline nylons, but flow-induced fiber orientation still creates differential shrinkage. The flow direction typically shows lower shrinkage than the transverse direction because carbon fibers align along the flow path. When designing bearing fits, bushing bores, and gear housings, the transverse direction should be checked separately because fiber orientation can produce dimensional differences that exceed the supplier’s nominal shrinkage value. Short-shot risk is greater with the 40% carbon fiber loading than with lower filler loadings because melt viscosity increases, especially at low shear rates. Gates and runners should be sized at the upper end of the design range for filled materials, and the runner system should be balanced to avoid asymmetric filling and differential fiber orientation.

Above the matrix glass transition region, which for many amorphous polyamides is near 120–155°C, flexural modulus decreases more rapidly than for semicrystalline PA 66. The high heat deflection temperature at 1.82 MPa reflects the carbon fiber network rather than the matrix alone, so HDT should not be used as the sole indicator of long-term load-bearing capability. Continuous service above 150°C requires creep-rupture testing or dynamic mechanical analysis under the actual temperature and humidity spectrum. Published creep data for this exact formulation is limited; therefore, prototype validation is required for load-bearing parts above 150°C.

Dimensional stability in humid service is usually better than that of PA 66 CF40 in thin-wall parts because the amorphous matrix exhibits less differential post-mold shrinkage. However, the amorphous grade may be more sensitive to combined high-temperature and high-humidity exposure than high-crystallinity PA 66. A useful screening protocol is to expose molded plaques to 80°C and 90% relative humidity for 500 h and then measure tensile strength and flexural modulus according to ASTM D638-14 and ASTM D790-17. A reduction in tensile strength above 20% indicates that the part design or service environment may require a different grade or a humidity-barrier coating.

Surface resistivity depends on fiber dispersion, part thickness, mold temperature, and gate design. When measured on molded plaques by ASTM D257-14, carbon-fiber-reinforced amorphous nylon at 40% often falls in the static-dissipative or conductive range below 1 × 10⁶ Ω/sq. However, plaque values should not be used directly for part qualification because resin-rich skin, weld lines, and flow-front hesitation create local high-resistivity zones. Surface resistivity should be measured on the actual production part using ASTM D257-14 or IEC 62631-3-2, with contact electrodes placed at the intended grounding path. The grade is not suitable for primary electrical insulation applications, and creepage distance calculations must account for the conductive carbon fiber surface.

If Replacing Semicrystalline PA 66 CF40 or PPS CF40, Where Are the Substantive Differences?

Substitution decisions should begin with a side-by-side comparison of dry-as-molded and moisture-conditioned properties. Compared with a typical carbon-fiber-reinforced PA 66 at 40% loading, RTP 287E offers lower mold shrinkage and more uniform shrinkage in the flow and transverse directions. The amorphous matrix reduces warpage in flat or thin-wall parts because it does not develop the large crystalline shrinkage anisotropy usually observed in semicrystalline PA 66. The trade-off includes lower notched Izod impact and potentially greater sensitivity to organic solvents. PA 66 CF40 often reports notched Izod impact above 85 J/m in the dry-as-molded state, whereas RTP 287E may fall in the 60–80 J/m range. The sharp crystalline melt of PA 66 near 260°C also helps PA 66 retain a higher fraction of its room-temperature flexural modulus up to 150°C when moisture content remains low. RTP 287E softens more gradually through its glass transition region and may require more conservative continuous-use temperature limits in humid service.

Against a 40% carbon-fiber-reinforced PPS, RTP 287E generally offers lower material cost and less demanding mold temperatures. PPS grades typically require mold temperatures of 135–150°C and may require post-crystallization cycles, while RTP 287E processes at mold temperatures below 100°C. However, PPS has superior long-term thermal stability above 200°C and better resistance to hot automotive fluids and steam condensate. For under-hood applications exposed above 175°C, RTP 287E should be evaluated for creep rupture, thermo-oxidative embrittlement, and dimensional growth; published data for this specific amorphous nylon formulation above 175°C is limited.

Compared with a 30% carbon-fiber-reinforced amorphous nylon, the 40% loading in RTP 287E increases tensile modulus and lowers the coefficient of linear thermal expansion, but it also raises melt viscosity and reduces flow length. Thin-wall parts below 1.0 mm nominal wall thickness may show short shots or non-uniform fiber packing if gate size is not increased. The higher carbon fiber content also lowers surface gloss and may produce visible flow lines, which should be considered for cosmetic parts. If a lower static-dissipative threshold or lower viscosity is required, the 30% carbon fiber grade may be more process-tolerant, but the design should be verified with the exact product code specified on the print.

Chemical resistance is generally good in dilute acids, aliphatic hydrocarbons, and common automotive oils, but concentrated strong acids, phenol, cresol, and some chlorinated solvents can attack the amorphous polyamide matrix. Combined stress and chemical exposure may cause environmental stress cracking, particularly at internal weld lines, knit lines, and molded-in stress. Chemical immersion testing should follow ASTM D543-21 or ISO 22088-3:2006 on stressed specimens. The supplier may provide regional compliance documentation for RoHS Directive 2011/65/EU and REACH SVHC, but grade-specific certification should be requested before use in regulated electronics or automotive applications. No blanket statement should be inferred for food-contact use under FDA 21 CFR unless the specific production lot is certified by the supplier.

For a metal-to-plastic conversion in an electronic housing produced on a 150-ton injection molding machine, the practical benefits of RTP 287E are most evident in flatness and hole-to-hole dimensional capability after moisture conditioning. The main processing risk is not melting the resin but maintaining fiber length and avoiding stagnant hot-runner degradation. Tooling should be validated with short shots, gate-seal studies, and dimensional capability runs at both 65°C and 95°C mold temperatures. The final part qualification should include surface resistivity mapping at the grounding path, tensile strength at an internal knit line, and dimensional growth after 500 h at 85°C/85% relative humidity. These measurements, anchored to ASTM D257-14, ASTM D638-14, and ASTM D790-17, provide the objective basis for accepting the material in production and for rejecting lots that drift outside the qualified processing envelope.