VESTAMID E62-S3 black is a polyether block amide (PEBA) moulding and extrusion compound based on nylon 12, supplied as black pellets. The product is classified as a thermoplastic polyamide elastomer under ISO 1874-1; the numeric suffix corresponds to the Shore D hardness class of 62 measured according to ISO 868, while the S3 designation identifies the standard moulding viscosity series. The macromolecular structure alternates semi-crystalline polyamide-12 hard segments with polyether soft segments. This arrangement provides elastic recovery without external plasticiser, retains the hydrocarbon resistance of nylon 12, and reduces the low-temperature brittleness associated with homopolymer nylon 12. Representative published values include a conditioned density of 1.01 g/cm³ (ISO 1183-1) and a dry-state tensile modulus near 300 MPa (ISO 527-1/-2). The black pigmentation is incorporated during compounding and does not eliminate the need for lot-specific thermal stabiliser verification.

What Limits Melt Stability During High-Shear Compounding?

Melt stability is controlled primarily by thermo-oxidative attack on the polyether soft segment. Ether linkages undergo radical abstraction at melt temperatures above 230 °C, producing chain scission and carbonyl degradation products. In a corotating twin-screw extruder with L/D 40:1, barrel temperatures from 190 °C to 230 °C are normally adequate. A flat barrel profile with the feed zone at 190 °C and the die at 220 °C limits local overheat. Screw speeds of 200 min⁻¹ to 350 min⁻¹ are suitable for 25 mm to 40 mm machines; higher speeds increase viscous dissipation and can raise local melt temperature beyond the degradation threshold. Residence time should remain below 5 min when processing at the upper end of the temperature window. Melt volume-flow rate may be monitored under ISO 1133-1 at 190 °C/2.16 kg, but lot-to-lot values must be confirmed against the certificate of analysis because polyether block content influences shear-thinning behavior.

Vented barrels are recommended during compounding to remove trace moisture and low-molecular-weight volatiles. Vacuum above -0.08 MPa is not required and may entrain molten polymer into the vent port. The material is shear-thinning, so increasing screw speed does not linearly improve dispersion; it can reduce residence time below the level required for uniform colour concentrate distribution. On production lines, melt pressure before the screen pack is a practical control variable. A pressure increase greater than 10 % over baseline at constant screw speed indicates insufficient drying, screen fouling, or degradation-induced viscosity shift. Silicone-based external lubricants should be avoided because they can interfere with downstream bonding, printing, or overmoulding adhesion.

Underwater pelletizing is preferred for continuous compounding. Strand pelletizing is possible if the strand bath water is held below 30 °C and the strand is cooled uniformly to prevent internal voids from trapped moisture. Surface roughness on the pellet can be corrected by lowering die temperature by 5 °C to 10 °C while maintaining melt pressure above 3 MPa.

Mechanical Response Under ISO 527-1/-2 Loading

Mechanical data are typically reported on specimens conditioned for 88 h at 23 °C and 50 % RH according to ISO 291. The material exhibits a distinct yield point under tensile loading, followed by cold drawing and high elongation. The polyether soft phase reduces tensile modulus relative to semi-crystalline homopolymer nylon 12, but the polyamide-12 hard segments provide sufficient load-bearing capacity for structural clips, couplings, and protective covers. Values below are representative for injection-moulded plaques and are not specification limits.

A “no break” Charpy result at -30 °C does not imply unrestricted energy absorption under multi-axial impact. Instrumented puncture testing according to ISO 6603-2 should be specified for thick sections or crash-loaded parts because the notched Charpy configuration is insensitive to plane-strain fracture modes. Water uptake is low relative to short-chain nylons, but saturated moisture can reduce tensile modulus by approximately 5 % to 10 % and increase elongation at break. Long-term humid service should be evaluated after conditioning according to ISO 1110 at 70 °C and 62 % RH.

Injection moulding trials on an 800 kN clamp force machine are commonly initiated at a melt temperature of 220 °C and a mould temperature of 30 °C. The screw should have a low-shear general-purpose geometry with L/D 20:1 to 25:1 and a compression ratio of 2.0:1 to 2.5:1. A non-return ring with adequate clearance is preferred because the melt has higher elasticity than homopolymer nylon 12. Holding pressure is set between 40 MPa and 60 MPa hydraulic, and back pressure is limited to 5 MPa to 10 MPa to avoid excessive shear heating. For wall thickness below 1.5 mm, injection velocity should be increased to prevent premature freeze-off. Cavity-to-cavity temperature variation greater than 5 °C can shift part mass by more than 0.3 % and alter shrinkage in multi-cavity tools.

Drying is critical before melt processing. Residual moisture must be below 0.10 % by mass, measured by ISO 15512 Method B. Drying in a dehumidified-air dryer at 80 °C for 4 h is standard for sealed-lot material. At ambient relative humidity above 60 %, drying time is extended to 6 h to 8 h, and open hoppers should be avoided. Splay, surface gloss loss, or weld-line cracking in black mouldings is a production-scale indicator of residual moisture above 0.15 %; such parts often show reduced notched impact strength at -30 °C despite acceptable visual appearance.

Mould shrinkage is anisotropic. Typical values are 0.8 % to 1.4 % in flow and 0.6 % to 1.2 % transverse, but flat-plaque measurement according to ISO 294-4 is required before tooling release. Gates should be placed away from high-stress service locations. Weld-line strength is improved when melt temperature remains above 220 °C and the weld is packed before the skin freezes.

When Shore Hardness Is the Primary Selection Constraint

Within the VESTAMID E series, Shore D hardness is a rapid classification but not a complete design value. E55-S3, E62-S3, and E70-S3 differ in polyether soft-phase content, which changes tensile modulus, low-temperature impact energy, and creep under sustained load. E55-S3 reports a Shore D hardness of 55 (ISO 868) and lower flexural modulus; it recovers more fully under cyclic strain but may deform excessively under a continuous stress of 1 MPa at 40 °C. E70-S3 reports a Shore D hardness of 70 and higher tensile strength, but the reduced polyether content increases flexural stiffness and reduces sub-zero ductility. E62-S3 black occupies the intermediate position and is selected where the part must survive repeated flexing at temperatures down to -40 °C without exceeding the stiffness limits of a 62 Shore D design.

The distinction from plasticized nylon 12 is significant. A plasticized nylon-12 grade can match Shore D 62 but relies on migratory plasticiser. Over time, plasticiser loss shifts hardness upward and can create surface tack or contamination. VESTAMID E62-S3 black does not contain external plasticiser. The polyether block is covalently bonded into the polymer backbone, so the Shore D 62 value is a bulk property of the segmented copolymer rather than an additive effect.

Selection should be based on the flexural modulus at the lowest service temperature. If a modulus below 200 MPa at -20 °C is required, E55-S3 is usually preferred. If a modulus above 500 MPa at 23 °C is required, E70-S3 is usually preferred. E62-S3 black serves the intermediate range.

Candidate load-bearing uses include pneumatic and hydraulic tubing, cable sheathing, protective covers, coupling elements, and sports equipment components subjected to low-temperature impact. In compressed-air tubing, wall thickness must be calculated from the maximum working pressure and burst pressure at 23 °C under ISO 7751. For annular seals, compression set under constant strain should be measured according to ISO 815-1; published data for this specific configuration is limited, so validation on the actual part cross-section is required.

Chemical resistance is consistent with nylon-12 chemistry but modified by the polyether phase. Resistance to aliphatic hydrocarbons, mineral oils, greases, and weak alkalis is generally adequate at temperatures below 60 °C. Strong mineral acids, especially hydrochloric acid above 10 % concentration, can hydrolyse amide linkages. High-pressure steam above 120 °C accelerates hydrolysis and should be avoided. Polar solvents such as dichloromethane, dimethylformamide, and concentrated phenol solutions can swell the material and induce environmental stress cracking under external load.

Food-contact and medical uses require explicit compliance work. The black formulation is not considered appropriate for long-term implant grades. If used in short-term medical devices, the component must be validated under ISO 10993-1, and the pigment package must be disclosed to the toxicological risk assessor. EU food-contact compliance is assessed under Regulation (EU) No 1935/2004 and the applicable plastics regulation; the final article must be tested for overall migration. REACH SVHC status and RoHS Directive 2011/65/EU Annex II maximum concentration values should be confirmed against the lot-specific certificate because black pigments and processing stabilisers can vary.

Storage stability is limited by moisture uptake. Sealed storage at 15–30 °C and 30–65 % RH is recommended. Partially used material should be re-dried before processing if exposed beyond 8 h. Published data for multi-component injection moulding and laser sintering of this specific black grade are limited; those process routes require separate adhesion and fusion validation because carbon black affects laser energy absorption and the polyether soft phase modifies melt coalescence.

Dynamic Fatigue Is Not Predicted by Single-Point Tensile Data

Dynamic service life under flexing is not derived from a single tensile value. Cyclic loading at frequencies above 1 Hz should be evaluated by flexural fatigue testing on notched or unnotched specimens replicating the production surface. The absence of notched Charpy fracture does not guarantee endurance at high strain amplitudes. Parts with sharp radii, weld lines, or surface scratches may transition from ductile to brittle failure at temperatures approaching the polyether glass transition. Cyclic strain at elongation above 20 % can promote hysteretic heating in thick sections; service conditions that combine high strain amplitude with frequency above 5 Hz require thermocouple measurement at the specimen core to confirm that internal temperature remains below 60 °C.