Evonik VESTAMID eCO E40 CC50 Nylon 12, Dry is a carbon-fiber-reinforced polyamide 12 compound supplied with a residual moisture content controlled below 0.10 % by weight according to ISO 15512. The eCO designation identifies the grade within the supplier’s mass-balance bio-circular feedstock program for polyamide 12; E40 denotes the base viscosity platform, and CC50 indicates a nominal 50 wt% carbon fiber reinforcement. The dry designation applies to material in sealed, aluminum-lined packaging; once opened, the resin should be processed or re-dried before molding. Typical quality parameters include filler content, moisture, density, melt volume-flow rate, and dried-state mechanical performance tested under ISO 527-1/-2, ISO 178, ISO 179-1, ISO 75-1/-2, and ISO 1133-1.

Dry-state tensile modulus for the carbon-filled formulation is approximately 35,000 MPa in the flow direction, with tensile strength at break near 320 MPa and nominal strain at break around 1.7 % when measured on standard multipurpose test specimens. Flexural modulus and flexural strength are reported under ISO 178 at approximately 30,000 MPa and 520 MPa, respectively; these values are representative and subject to lot-to-lot and fiber-orientation variability. The high carbon fiber content reduces electrical resistance, but the exact value depends on injection speed, mold temperature, and gate geometry. For electrically demanding applications, molded plaques should be tested per IEC 62631-3-2 for volume resistivity and ASTM D257 for surface resistivity rather than relying solely on supplier specimen data. The density of the reinforced compound is approximately 1.31 g/cm³ by ISO 1183-1, compared with approximately 1.01 g/cm³ for unfilled VESTAMID E40.

How Does 50 wt% Carbon Fiber Content Alter Melt Rheology and Tooling Requirements?

The replacement of unfilled polyamide 12 with a 50 wt% carbon fiber compound changes flow behavior from a nearly Newtonian melt in the processing shear range to a strongly pseudoplastic suspension with wall-slip tendencies at high shear rates. Single-point melt volume-flow rate values, measured according to ISO 1133-1, should not be used as a substitute for capillary rheometry when modeling injection pressure or balancing multicavity tools. Characterization at shear rates of 100 s⁻¹ through 10,000 s⁻¹ reveals viscosity decay that depends on fiber length distribution and sizing chemistry. On production lines using 80 t to 250 t injection molding machines, the compound typically requires barrel temperatures from 240 °C to 260 °C; lower settings increase fiber orientation but risk poor homogenization and surface delamination. Mold temperatures between 60 °C and 100 °C are used, with the upper end selected when lower surface resistance and smoother carbon-filled surfaces are required. The material’s melting temperature, measured by differential scanning calorimetry per ISO 11357-1/-3, is near 176 °C, while the heat deflection temperature at 1.8 MPa is near 215 °C under ISO 75-1/-2. These thermal transitions do not imply that the polymer matrix remains stable at the HDT value; the grade is a semi-crystalline PA12 with a long-chain aliphatic backbone, and continuous thermal aging resistance must be evaluated under the specific environmental temperature and load.

Wear and screw design are operational constraints. Carbon fiber abrasion increases clearance on standard nitrided barrels and bimetallic check rings; therefore hardened tool steel or carbide-coated components are used. Screws with a low compression ratio and gradual transitions from feed to metering preserve fiber length and reduce dead spots. On 25 mm to 50 mm diameter reciprocating screws, shot sizes should be maintained between 30 % and 70 % of maximum barrel capacity to avoid excessive residence time. High backpressure settings above 5 MPa can accelerate fiber breakage and increase melt temperature without improving dispersion because the fibers are not agglomerated like pigments. For hot-runner systems, externally heated manifolds with large flow channels and low-shear valve gates are preferred; sequential valve-gate control can reduce knit-line strength loss in complex parts by managing fiber flow fronts. Knit lines in carbon-filled PA12 are zones of reduced tensile strength, typically retaining 40 % to 60 % of the nominal flow-direction strength; mold filling analysis should place knit lines away from structurally loaded sections when possible.

When the selection is narrowed to polyamide 12 compounds, the main alternatives to the CC50 grade are unfilled VESTAMID E40, glass-fiber-reinforced PA12, and lower-carbon-fiber-content PA12. Unfilled VESTAMID E40 has a dry tensile modulus near 1,600 MPa and elongation at break above 200 %; it is suitable for clips, tubing, and flexible snap-fit components. The CC50 grade shifts the property envelope to high stiffness but sacrifices ductility and notched impact. A glass-fiber-reinforced PA12 with similar filler content typically exceeds 1.45 g/cm³ in density and does not provide the same electrical conductivity or surface behavior. Compared with fossil-derived VESTAMID E40 CC50, the eCO version is processed within the same thermal and rheological window; the difference is limited to feedstock accounting and mass-balance certification, not polymer chemistry. The eCO attribute must be specified in the purchasing document if bio-circular allocation is required, because the suffix is not merely descriptive and should be matched to the supplier’s sustainability certificate.

When Thermal Stability and Chemical Resistance Requirements Exclude Lower-Melting Polyamide Grades

The long-chain PA12 backbone provides lower saturated water absorption than PA6 and PA66; this translates into more stable dimensions and less plasticization in humid environments. Values for water absorption at saturation are typically below 2.0 % for the carbon-filled grade, compared with over 9 % for PA66 under comparable immersion. The difference is critical in actuator housings, structural brackets, and fuel-system components exposed to condensation or splash. However, PA12 is not inherently hydrolysis-proof; it absorbs moisture slowly and must still be dried before melt processing. At 23 °C and 50 % relative humidity, open containers begin to gain moisture at the resin surface, and a drying step of 4 h to 12 h at 80 °C in dew-point-controlled dry air is recommended. Overdrying does not improve flow above the dry baseline and can accelerate yellowing or additive migration if temperature exceeds 100 °C for extended time.

Chemical compatibility of the carbon-filled grade remains governed by the PA12 matrix. Dilute acids, alkaline solutions, aliphatic hydrocarbons, lubricating oils, and many automotive fluids are generally compatible at low temperature, but concentrated sulfuric acid, formic acid, phenols, chlorinated solvents, and strong oxidizing agents can degrade the polymer. The carbon fiber reinforcement is inert in many environments but may promote galvanic coupling when the molded part is in direct contact with unprotected aluminum or magnesium in the presence of an electrolyte. Insulating washers, coatings, or nonconductive inserts are required in such assemblies. Thermal aging in air above 120 °C for extended periods can embrittle the PA12 matrix; reliance on HDT data alone for continuous-use temperature is not valid. Carbon-fiber-filled PA12 does not possess the long-term thermal oxidative stability of PEEK, PPS, or high-temperature polyamides and should not be specified for service above the supplier’s published continuous-use temperature for the unreinforced base polymer.

Carbon fiber loading in the range of 50 wt% produces enough fiber-to-fiber contact to create a conductive network in the melt and in the finished part, but the part surface may remain resin-rich under certain molding conditions. Surface resistivity measured per ASTM D257 can therefore range from 10² Ω/sq to 10⁵ Ω/sq, while volume resistivity per IEC 62631-3-2 may be more stable in the core. Fast injection speeds and high mold temperatures typically reduce the resin skin thickness and improve surface conductivity; slow filling and cold mold surfaces can insulate the surface. For electrostatic discharge control, molded parts are validated according to IEC 61340-5-1 using specified electrode configurations, not only material coupons. The grade’s conductive nature also affects short-circuit clearance in electronic housings; creepage and clearance distances must be re-evaluated because the insulating polymer cannot be relied upon as electrical isolation. When paint adhesion or adhesive bonding is required, surface treatment for carbon-filled PA12 may include plasma or adhesion promoters; mold release agents containing silicone can interfere with bonding and should be avoided unless post-mold surface cleaning is validated.

Dimensional Control and Shrinkage Anisotropy in the Dry Carbon-Fiber Formulation

Mold shrinkage in the CC50 grade is markedly anisotropic. Flow-direction shrinkage is often below 0.10 %; transverse shrinkage may reach 0.40 % in flat plaques. The difference arises because carbon fibers align along the flow path, restricting contraction parallel to the fiber axis while leaving the transverse PA12 matrix free to shrink. This behavior cannot be corrected by drying the resin; it is a directional filler property. For close-tolerance parts, gate positions should be arranged so that the primary load or precision axis aligns with fiber orientation, or the component should be designed with symmetric wall thickness to reduce warpage. Mold temperature uniformity is critical; a temperature difference of 10 °C across the cavity can create differential crystallization and amplify warpage beyond shrinkage predictions. Dimensional audits should include measurement after 24 h conditioning at 23 °C and 50 % relative humidity, because post-mold crystallization and moisture equilibration can shift critical dimensions by 0.05 % to 0.15 %.

Because the material is delivered dry, the principal processing boundary is control of ambient exposure. A sealed aluminum-lined bag can be kept without drying until the moisture barrier is damaged. Once opened, material should be consumed within the shift or transferred to a dry-air hopper with a dew point below -30 °C. Drying at 80 °C for 4 h is generally sufficient for surface moisture; material that has been exposed for several days at high humidity may require up to 12 h. The use of hot-air ovens without dew-point control is not recommended because humid air can maintain an equilibrium moisture level above the processing target. Regrind from sprues and runners can be added at up to 30 wt%, but each regrind pass reduces fiber length and notched Charpy impact. If the regrind contains burned material from hot-runner degradation, melt filtration pressure rise and electrical conductivity variability may increase. The material should not be blended with glass-fiber-reinforced PA12 or unfilled PA12 without evaluating layer adhesion and shrinkage mismatch.

Lot-to-lot variability in filler content and fiber length distribution is controlled by the supplier, but mechanical properties on molded parts are influenced by machine type, gate geometry, and processing conditions. First-article qualification should therefore include tensile bars, flexural bars, and Charpy specimens molded in the same tool family as production components, not only laboratory plaques. Published data for high-cycle fatigue, creep, and chemical aging of this specific bio-attributed formulation are limited; design validation should rely on application-specific testing under the expected load, temperature, and media exposure rather than short-term datasheet values alone.