Evonik VESTAMID® X7393 black 9.7507 is a pigmented polyamide 12 (PA 12) compound identified by the manufacturer as an extrusion-grade material within the VESTAMID family. The designation X7393 identifies the base resin and additive package; the suffix black 9.7507 specifies the integrated black color registration. The material is supplied as cylindrical pellets and is processed primarily on single-screw extrusion lines for flexible conduit, cable sheathing, and small-diameter tubing. In these applications, the PA 12 backbone reduces equilibrium water absorption and improves dimensional stability relative to PA 6 and PA 66, while the black pigmentation provides ultraviolet screening and opacity.

In comparison with other polyamides, the PA 12 structure provides lower equilibrium moisture uptake than PA 6 or PA 66 and maintains ductility at sub-zero temperatures. Compared to PA 11, PA 12 has a similar long-chain hydrocarbon spacing but a lower melting range; both are low-moisture engineering polyamides. The pigmented black 9.7507 version differs from natural or unpigmented VESTAMID grades in that the carbon black package raises viscosity, affects surface appearance, and improves ultraviolet screening. These differences must be quantified on the production line because colorant type and loading can shift melt-flow and mechanical properties.

For incoming inspection, density is measured per ISO 1183-1 and is generally expected in the range of 1.01–1.03 g/cm³ for unreinforced PA 12. The melting transition by differential scanning calorimetry per ISO 11357-3 typically falls between 172°C and 180°C. Vicat softening temperature per ISO 306 method B50 may lie between 140°C and 165°C depending on modification and pigment loading. These values are class-typical for PA 12; the lot-specific datasheet for VESTAMID X7393 black 9.7507 must be referenced for exact specification limits.

How Does the PA 12 Amide Density Control Water Absorption and Dimensional Stability?

Water uptake in polyamides is governed by the concentration of amide linkages along the polymer chain. PA 12 contains one amide group per C12 repeat, a lower amide density than PA 6 or PA 66. Equilibrium water absorption at 23°C in water per ISO 62 is therefore lower for PA 12; unreinforced PA 12 typically reaches 0.6–0.8 wt%, PA 66 reaches approximately 7–8 wt%, and PA 6 reaches approximately 9–10 wt%. The lower uptake reduces swelling and hydrolysis potential of VESTAMID X7393 black 9.7507 in humid service and limits the decrease in glass transition temperature caused by absorbed water.

Moisture control before extrusion is nevertheless mandatory. Hydrolysis of amide groups in the melt begins when pellet moisture exceeds approximately 0.10–0.15 wt%. In production, a dehumidifying hopper dryer with a dew point of −30°C or lower is operated at 70–80°C for 4–6 h. Drying above 90°C is not recommended for black grades because the dark surface absorbs infrared heat unevenly and can develop surface oxidation or color drift. Measurement of residual moisture by Karl Fischer titration or a calibrated moisture analyzer is preferred to timed drying alone.

For cable-sheathing and tube applications, the lower equilibrium moisture uptake translates into more stable dielectric properties after conditioning per IEC 62631-3-1 and lower dimensional movement at 50% relative humidity per ISO 291. Exact resistivity and permittivity values are formulation-dependent and must be taken from the grade datasheet.

Barrel temperature profiles for single-screw extrusion of black PA 12 are derived from the melting range, not from an arbitrary fixed setting. A general-purpose extruder with an L/D ratio of 24:1 to 30:1 and a compression ratio of 2.5:1 to 3.5:1 is used; barrier screws with shear-mixing sections disperse the black pigment and reduce carbon black agglomerates. Typical zone settings are 170–190°C in the feed, 200–230°C in compression, 210–240°C in metering, and 210–230°C at the die. Melt temperature measured at the die with an immersion thermocouple should be maintained below 250°C. Residence time at melt temperature should not exceed 8–10 min because thermally stabilized PA 12 can still form gel particles or undergo slow viscosity drift in dead zones.

Screen-pack configuration is a critical control point. A breaker plate with 100–150 μm screens removes pigment agglomerates and incidental contamination. On production-scale lines, progressive screen blinding by carbon black aggregates raises screw-tip pressure; the pressure transducer is used to initiate screen changes. A melt pump may be inserted between the extruder and die to reduce pressure pulsation on thin-wall tube and cable jackets. Batch-to-batch melt-flow variation can be checked by ISO 1133-1 at 235°C with a 5 kg load; deviations beyond the producer's certificate of analysis indicate lot-to-lot dispersion or molecular-weight differences.

Tensile Yield, Creep, and Low-Temperature Impact Test Frameworks

Mechanical characterization follows ISO 527-1/-2 for tensile properties and ISO 179-1/1eA or ISO 180 for impact. Unreinforced PA 12 at 23°C and 50% relative humidity typically shows a tensile modulus of 1100–1400 MPa, while flexible or impact-modified grades may fall to 300–600 MPa. The yield stress of unmodified PA 12 is commonly 35–45 MPa; flexible grades may not exhibit a distinct yield point and are characterized by nominal strain at break above 200%. VESTAMID X7393 black 9.7507 should be tested as-pigmented, because carbon black can slightly shift modulus through nucleation or particulate reinforcement.

Low-temperature impact is evaluated at 23°C, −30°C, and −40°C on specimens conditioned per ISO 291. Many flexible PA 12 compounds show no break at 23°C and high retained impact at low temperature. The notch radius, test energy, and conditioning history must be reported with the value; a Charpy value without notch type and moisture condition is not comparable across laboratories.

Creep behavior is assessed by ISO 899-1. Because PA 12 absorbs less water than PA 6 and PA 66, the plasticizing effect of moisture on creep under constant load is smaller. At 23°C and 50% RH, the creep modulus of unreinforced PA 12 after 1000 h may range from 500 MPa to 800 MPa depending on stress and grade; published data for this specific black-flexible configuration is limited, and long-term design values should be derived from lot-specific tensile creep curves.

Corrugated tube lines for PA 12 electrical conduit are commonly configured with vacuum sizing, water-spray cooling, and a corrugator capable of 20–60 kPa vacuum. Melt temperature is held at 215–235°C; the die is set to compensate for moderate die swell. Cooling water temperature is normally maintained at 15–25°C to avoid quench-induced surface defects and to stabilize the corrugation pitch. In cable sheathing, line speeds of 300–1200 m/min are used depending on insulation thickness and extruder output; a melt pump stabilizes diameter. The black 9.7507 pigment is selected to reduce ultraviolet transmittance through the jacket and to provide visible surface quality. Poor pigment dispersion appears as raised agglomerates, pinholes, or gloss variation on the tube surface, and is corrected by increasing shear mixing or verifying the pigment masterbatch compatibility.

Before cable extrusion, pellet moisture must be below 0.10 wt%; storage at relative humidity above 60% re-qualifies the material for drying. In flexible PA 12 lines, excessive moisture produces silver streaks and melt-strength loss in the cone between die and cooling water, while excessive melt temperature produces surface oxidation and potential gel particles in the die lip. These failure modes are observable on production-scale extruders and are used to set alarm limits for melt pressure and melt temperature.

When the Black 9.7507 Colorant Package Alters Thermal-Oxidative Stability and UV Resistance

Carbon black in a PA 12 matrix acts as an ultraviolet absorber and free-radical scavenger. Accelerated weathering per ISO 4892-2 with xenon-arc lamps and daylight filters evaluates color change by ISO 11664-4 or ASTM D2244 and retention of tensile properties after 500–1500 h. The protection level depends on carbon black primary particle size, aggregate structure, and dispersion. A well-dispersed furnace black with primary particle size below 25 nm provides higher UV screening than larger-particle grades. However, high carbon black loadings increase melt viscosity and can reduce elongation at break, so weathering performance and processability are balanced by the compound supplier.

Thermal-oxidative stability is assessed by oven aging per ISO 188 at 100°C and 120°C. The relevant end-point is often retention of elongation at break or impact, not color shift, because the black pigment masks yellowing. For black PA 12 cable sheathing, long-term aging must also be evaluated against end-product flame propagation or smoke tests such as IEC 60332-1-2 or UL 1581, which are cable-level tests and not intrinsic polymer properties.

Consult the Lot-Specific Datasheet Before Qualifying Fuel-Vapor and Air-Brake Tube

PA 12 is used in automotive fuel-vapor and air-brake tubing because of its resistance to aliphatic hydrocarbons, diesel, and ozone. Chemical resistance is evaluated per ISO 175 by immersion in test fluids at 23°C and 60°C. Dimensional change, mass change, and tensile retention are recorded after 7 days and 28 days. In fuel contact, the amide group provides a barrier to hydrocarbon permeation; however, polar alcohols and moisture can plasticize the amorphous phase and lower yield stress. The combination of fuel and zinc chloride road salt is particularly aggressive for polyamides because zinc chloride can penetrate micro-cracks and induce stress cracking under high hoop stress.

For VESTAMID X7393 black 9.7507, suitability for fuel-vapor or air-brake tubing must be confirmed through end-product testing per SAE J844 or ISO 7628, including pressure cycling, burst strength, and environmental stress-cracking resistance. The flexible formulation of X7393 may require a lower service pressure or thicker wall compared to rigid PA 12 grades; the black pigmentation does not inherently alter chemical resistance, but pigment agglomerations can act as stress concentrators under high pressure. In production, a filtration step before the die is therefore as important for mechanical integrity as it is for surface quality.

Regulatory documentation for VESTAMID X7393 black 9.7507 must be obtained from Evonik for the specific lot and destination market. The base PA 12 polymer may be evaluated under FDA 21 CFR 177.1500 for repeat-use food-contact articles and under Regulation (EU) No 10/2011 on plastic materials intended for food contact, but the black pigment and any processing aids must be assessed separately. Under the RoHS Directive 2011/65/EU, lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ethers are restricted to their maximum concentration values; a compliant black PA 12 must not rely on restricted heavy-metal pigments. REACH Regulation (EC) No 1907/2006 requires communication of substances of very high concern above 0.1 wt% in the article. A change in the color package suffix from natural to black can affect the chemical inventory and should be verified before import or export.