LATI Latamid 12 CP/85 is a carbon-powder-modified polyamide 12 compound supplied by LATI Industria Termoplastici S.p.A. The CP/85 designation is read as a PA 12 matrix containing approximately 15% by weight conductive carbon powder, with the remaining 85% composed of polylaurolactam resin and stabilizer package. The filler is non-fibrous; the conductive particulate forms a percolating network that lowers surface and volume resistivity, while the PA 12 backbone retains lower equilibrium moisture uptake than PA 6 or PA 66 and lower density than short-carbon-fiber PA 12 alternatives. The material is supplied in black pellet form and is intended for injection-molded parts where carbon-fiber reinforcement is not required but electrostatic dissipation, dimensional stability, and hydrocarbon resistance are specified.

Compared with unfilled PA 12, the carbon-powder grade raises tensile modulus and lowers surface resistivity. Compared with a fiber-reinforced PA 12 grade, it produces more isotropic shrinkage and lower warpage at the cost of flexural modulus. Product-specific values published in open secondary sources are limited; the data that follow describe the typical property envelope for conductive carbon-powder-filled PA 12 and should be validated against the current LATI technical datasheet for this exact grade.

What Distinguishes This Powder-Filled Grade from Fiber-Reinforced PA 12?

Structural anisotropy is the primary differentiator. Carbon powder particles have an aspect ratio close to 1–10 after dispersion, whereas short carbon fibers in a 15% fiber-filled PA 12 often retain length-to-diameter ratios above 20–50. The low aspect ratio minimizes flow-induced orientation during cavity filling. Consequently, the difference between flow-direction and cross-flow mold shrinkage in carbon-powder grades is typically less than 10–15% of the nominal shrinkage, while short-fiber grades can exhibit anisotropy ratios above 1.5–2.0 in thin-wall sections. This difference is measured by ISO 294-4 on standardized plaques and is relevant for annular parts, connector shrouds, and snap-fit housings where warpage is an assembly-critical defect.

Electrical conductivity in the powder-filled grade arises from interparticle contact and tunneling; a continuous conductive fiber network is not required. The percolation threshold for carbon black in a PA 12 matrix is commonly reported between 3% and 8% by weight, depending on carbon-black structure, surface area, and dispersion. At a 15% loading, the material moves into the conductive regime rather than the merely antistatic regime, with surface resistivity typically below 10⁵ Ω/sq when tested according to IEC 62631-3-2 on conditioned plaques. A short-carbon-fiber PA 12 grade at the same loading does not automatically reach the same surface resistivity because the fiber network may be separated by polymer-rich surface layers unless a conductive sizing is used.

Mechanically, the powder-filled grade occupies a middle position. Tensile modulus for conductive carbon-powder-filled PA 12 of this class is commonly in the range 1800–2600 MPa, whereas unfilled PA 12 may show 1300–1600 MPa and a 15% carbon-fiber PA 12 may reach 5000–7000 MPa. The test method is ISO 527-1/-2 at 23°C and 1 mm/min for modulus. The powder-filled grade does not provide the high stiffness of fiber reinforcement, but it avoids the strong fiber-induced anisotropy in weld lines and gate regions. For applications such as fuel-system retention clips, sensor brackets, and conveyor contact pads, warpage control and electrical dissipation are often weighted more heavily than flexural modulus.

The table values are class-level ranges for orienting material selection. For the exact LATI Latamid 12 CP/85 formulation, the current supplier datasheet remains the controlling reference; batches can vary within the specified tolerance, and conditioned values depend on plaque thickness, mold temperature, and moisture history.

In humid service, PA 12 is specified because its equilibrium moisture uptake is lower than that of PA 6 or PA 66. At 23°C and 50% RH, PA 12 absorbs approximately 0.6–0.8% moisture, while PA 6 may take up 2.5–3.0% and PA 66 2.0–2.5%. The lower moisture uptake reduces dimensional change and modulus loss in damp environments. For the carbon-powder-conductive PA 12 grade, moisture uptake does not control the conductive network, because carbon-particle contacts are not dependent on dissolved water. However, moisture swelling can alter contact pressure in assembled snap-fits and should be considered in tolerance stackups. The relevant test for physical property retention after moisture conditioning is ISO 1110 accelerated conditioning, followed by ISO 527-1/-2 tensile testing.

Short-term heat resistance of this class is commonly reported through heat deflection temperature. Under ISO 75-2 method B at 0.45 MPa, conductive carbon-powder-filled PA 12 typically shows values in the range 130–150°C; at 1.8 MPa, values may be 55–70°C. These ranges are not product datasheet values; they indicate the class effect of the PA 12 matrix and particulate filler. Continuous-use temperature in air is limited by thermal-oxidative stabilization and end-use stress, not by a single heat deflection value. Long-term thermal aging performance should be evaluated by ISO 4577 or supplier-specific testing at the required exposure temperature.

Chemical compatibility follows the PA 12 backbone. PA 12 is resistant to many aliphatic hydrocarbons, oils, greases, fuels, and hydraulic fluids, and is less affected by zinc chloride solutions than PA 6 or PA 66. The carbon-powder network is inert to the same fluids. However, strong oxidizing acids, phenols, and hot formic acid are outside the intended service envelope. The grade should not be specified for continuous immersion in hot strong mineral acids or for contact with amine-rich additives that could plasticize the polyamide and disrupt conductive particle contacts. Chemical resistance testing is commonly performed by ISO 175 or ISO 22088-1, with post-exposure tensile retention measured by ISO 527-1/-2.

Rheological behavior of the carbon-powder-filled melt differs from unfilled PA 12. The filler increases apparent melt viscosity at low shear rates and reduces die swell. Melt volume-flow rate, if reported, would be measured by ISO 1133-1:2022 at 235°C with a 2.16 kg load for polyamide grades. However, the carbon-filled grade is better characterized by capillary rheometry at 240°C and 100–1000 s⁻¹ because MVR data alone do not capture the shear-thinning behavior of the filled melt. A typical capillary flow curve for this class shows apparent viscosity falling from 150–250 Pa·s at 100 s⁻¹ to 40–80 Pa·s at 1000 s⁻¹. Product-specific flow data for Latamid 12 CP/85 should be obtained from the supplier’s injection-molding simulation dataset or measured on the actual lot before setting gate velocity profiles.

Processing Boundaries on a Reciprocating-Screw Injection Machine

The pellets must be dried before molding when storage has exposed them to ambient humidity above 40% RH. A dehumidifying dryer with desiccant bed and dew point at or below −30°C is recommended, not a hot-air cabinet dryer. At a bed temperature of 80–90°C, residence time of 4–8 h is sufficient to reduce residual moisture below 0.10%, measured by ISO 15512 method B. Molding with residual moisture above 0.15% causes surface splay, lower weld strength, and may reduce Charpy notched impact by more than 20% relative to dry resin.

Injection molding is typically performed on a three-zone reciprocating-screw machine with a general-purpose screw of 20:1 to 25:1 L/D and compression ratio 2.0:1 to 2.5:1. The barrel temperature profile from rear to front is set at 220–230°C, 230–250°C, 240–260°C, and nozzle 245–265°C. Melt temperature measured by infrared pyrometer should remain between 240°C and 270°C. Temperatures above 280°C are not recommended because prolonged residence at high temperature can degrade the carbon powder surface and the polyamide chain. Mold temperature is held between 40°C and 80°C; higher mold temperatures in that range improve knit-line strength and reduce surface skin orientation but extend cooling time.

In production-scale trials with thin-wall connector housings below 0.8 mm nominal wall, short shots become frequent when the nozzle thermocouple falls below 245°C and mold side walls are below 50°C. The runner and gate should be sized to avoid shear heating above 15,000 s⁻¹; carbon-filled melts can exhibit non-Newtonian shear-thinning, but excessive gate shear can locally degrade the conductive network and produce surface marks. A screw back pressure of 0.3–0.7 MPa and screw rotation below 100 min⁻¹ are starting conditions for homogeneous carbon-powder dispersion without excessive work input. Hold pressure is commonly set at 50–70% of first-stage injection pressure, and gate-seal time is determined by part-weight stabilization, typically after 6–10 s for cold-runner molds with wall thickness 2.0 mm.

Tool design for this grade benefits from a slightly larger gate thickness than unfilled PA 12 because the filled melt can freeze more quickly at the gate. Submarine gates should use diameters of 0.8–1.2 mm for small parts, and edge gates should be at least 60% of the nominal wall thickness. Runner diameters below 3.0 mm can increase shear heating and pressure loss in cold-runner molds. Hot-runner systems should use internally or externally heated nozzles with temperature control within ±2°C to prevent stagnation and carbon degradation. Venting is required because the grade can generate gases at high processing temperatures; vents of 0.02–0.04 mm depth on the parting line help prevent burn marks, especially at flow-front meeting points.

On production lines, batch-to-batch variation in carbon-powder surface area and moisture content can shift the percolation state and the melt flow. Incoming lots should be checked for moisture by ISO 15512 and for apparent melt viscosity at a fixed shear rate. Ready-to-mold compounds do not require dry-blending by the processor because carbon powder is already compounded by the supplier. However, extended storage in humid warehouses can require re-drying and may slightly increase moisture content above 0.10% even in sealed containers if the liner is damaged.

When Electrical Decay Time Is More Decisive Than Flexural Modulus

The grade is often selected for electrostatic discharge control rather than structural stiffness. Candidate parts include fuel-line clips, sensor bodies, robot gripper pads, conveyor contact blocks, and enclosure components where triboelectric charge must be drained to ground. The controlling test may be IEC 61340-2-3 charge-decay measurement or IEC 62631-3-2 surface resistance. Samples are conditioned for 24 h at 23°C and either 12% RH or 50% RH. For conductive carbon-powder-filled PA 12 of this class, surface resistivity is typically below 10⁵ Ω/sq; charge-decay times from 1000 V to 100 V are commonly below 2 s for molded plaques. Published decay-time data for this exact LATI grade are limited; qualification should therefore use the same thickness and electrode configuration as the end-use molded part.

Electrostatic decay measurement requires defined electrode geometry. In IEC 61340-2-3, a charge of 1000 V is placed on the specimen and the time to fall to 100 V is recorded. For conductive materials with surface resistivity below 10⁵ Ω/sq, the decay time is often below 0.1 s; however, probe contact resistance and specimen size can dominate the measurement. The end-user qualification should specify plaque dimensions of at least 100 mm × 100 mm and electrode separation of 50 mm. Values below 10² Ω/sq are possible after surface contamination but should not be expected under dry conditions. Volume resistivity may be measured by ASTM D257 or IEC 62631-3-1; class-typical values for conductive carbon-powder PA 12 are between 10¹ and 10³ Ω·cm.

Unlike humidity-dependent antistatic additives, carbon-powder conductivity is not controlled by dissolved water in the polymer. The conductive network remains stable under dry conditions, after washdown cycles, and after thermal aging below the polyamide’s continuous-use temperature. However, the carbon-powder filler produces a black surface and reduces the mirror-like appearance available with unfilled natural or colored PA 12. The weld-line strength is also lower than that of unfilled PA 12 because the carbon particles can align in the weld plane and reduce molecular interdiffusion at the knit line. In a multi-gated connector body, weld-line tensile strength may be 20–40% lower than the bulk tensile strength measured by ISO 527-1/-2 on a single-gate tensile bar. Gate location must therefore be optimized to move weld lines away from snap-fit roots and sealing faces.

Within the LATAMID 12 family, the CP/85 grade should be compared with carbon-fiber grades such as LATAMID 12 C/15. The C/15 grade contains short carbon fiber and provides higher stiffness but may require post-molding conductivity audits because surface resistivity can vary with skin orientation and fiber concentration at the part surface. The CP/85 grade uses carbon powder to achieve conductivity more uniformly through the part cross-section. The difference is particularly relevant for parts machined or abraded after molding: a powder-filled part continues to conduct through the core, while a fiber-filled part may expose insulating polymer-rich core regions after machining. The appropriate test is IEC 62631-3-2 on a cut or abraded surface, not only on the molded skin.

The grade’s structural operating boundary is its tensile modulus. If a housing or bracket requires modulus above 3000 MPa at 23°C, a short-carbon-fiber-reinforced PA 12 is likely required, but the fiber-filled alternative may need a conductive sizing to reach the same surface resistivity and may show higher warpage due to fiber orientation. If the modulus requirement is below 1800 MPa and static-dissipative behavior is sufficient, an unfilled PA 12 with antistatic additive may be considered, but its surface resistivity is humidity-sensitive and may rise above 10¹² Ω/sq after prolonged dry storage. The carbon-powder grade is positioned between those two alternatives: it provides stable low resistivity without the anisotropy of fiber reinforcement, within the stiffness and appearance constraints described above. The compound is black as supplied and cannot be matched to light colors because carbon powder dominates optical absorption. Regulatory compliance with RoHS Directive 2011/65/EU and REACH depends on the exact stabilizer package and carbon-black grade and must be confirmed against the supplier’s current certificate.