Evonik Vestamid E55-S3 Heat & Light Stabilized Nylon 12/PEBA Elastomer is a polyether block amide (PEBA) thermoplastic elastomer in which the hard segment is nylon 12 and the soft segment is a polyether diol. The product is specified at 55 Shore D hardness according to ISO 868, placing it between the softer Vestamid E40-S3 and the harder Vestamid E58-S4 and E62-S3 grades. The S3 suffix identifies a heat- and light-stabilization package intended for prolonged thermal and ultraviolet exposure during melt processing and outdoor service. Industrial applications include pneumatic control lines, fuel vapor tubing, hydraulic hose jackets, cable sheathing, sports shoe components, conveyor belt segments, and seals. Unlike plasticized polyamide 12 or selected thermoplastic polyurethanes, flexibility in Vestamid E55-S3 is a consequence of block copolymer architecture rather than external plasticizer addition; therefore low-temperature flexibility and surface non-tack do not depend on plasticizer retention.

The values in Table 1 are representative lot-averaged data from standard test methods, not guaranteed specification limits; lot-to-lot variance and specimen conditioning influence the results, particularly elongation at break and tear strength.

Production-scale drying experience on twin-screw extruders with 25:1 to 40:1 L/D shows that residual moisture is the dominant cause of viscosity fluctuation and surface roughness in PEBA melts. The granulate is dried in desiccant dryers with a dew point below -30 °C at 80–100 °C for 4–8 h, reducing moisture to below 0.05 % by Karl Fischer analysis according to ISO 15512. If the material is exposed to ambient air for more than 2 h at 50 % RH, re-drying is required. Vacuum venting in twin-screw compounding or direct degassing extrusion at 0.08–0.09 MPa absolute pressure removes residual volatiles but does not replace upstream drying. Hopper residence time at 100 °C should be limited to 12 h to prevent oxidative yellowing. Batch-to-batch variance in melt viscosity, measured by melt volume-flow rate according to ISO 1133-1 at 230 °C and 5 kg load, is typically controlled to ±10 %; converters observe that variations within this band still require adjustment of barrel temperature profile by 5–10 °C to maintain constant die pressure on single-screw extrusion lines. Failure modes associated with inadequate drying include melt fracture, surface sharkskin, and bubbles in transparent or thin-walled tubes; these are not corrected by increasing die temperature, which instead accelerates surface oxidation.

How Does the S3 Stabilization Package Influence Long-Term Thermal and UV Performance?

The S3 stabilization package is directed primarily at the oxidative vulnerability of the polyether soft segment, which is more susceptible to radical attack than the nylon 12 hard segment. In accelerated weathering per ISO 4892-2, test specimens are subjected to xenon-arc irradiation with a daylight filter at 0.35 W/m² at 340 nm, black-standard temperature 65 °C, and water spray cycles; acceptance is usually expressed as retention of tensile elongation after 1000 h or 2000 h. Published data for this specific configuration is limited, and the stabilizer depletion rate is influenced by wall thickness and surface-to-volume ratio. In air-oven ageing per ISO 188, retention of notched Charpy impact strength after exposure at 100–120 °C is an indicator of hard-segment integrity; short-term excursions to 150 °C are tolerated only for minutes. The package typically combines a hindered phenolic antioxidant and a hindered amine light stabilizer (HALS), though the exact composition is proprietary. The HALS migration rate in thin films below 100 µm can become a limiting factor for ultraviolet stabilization homogeneity. Stabilizer performance is also assessed by yellowness index change per ASTM E313 after multiple extrusion passes; a change of less than 2 yellowness units after three passes at 230 °C is considered indicative of adequate thermal stabilizer distribution, but published data for this specific configuration is limited.

Pneumatic control lines made from Vestamid E55-S3 are typically extruded as monolayer tubes with outer diameters from 4 mm to 16 mm and wall thickness from 0.5 mm to 2.0 mm. Burst pressure is validated by hydrostatic testing per ISO 1402 or SAE J343; published data for this specific configuration is limited for barbed-fitting assemblies. Hydraulic hose jackets require abrasion resistance; Taber abrasion testing per ISO 5470-1 is used with H-18 wheels and 1000 g load, but end-use validation is required because oil-soaked specimens can show reduced abrasion resistance. Cable sheathing is extruded at line speeds from 25 to 150 m/min; surface energy after corona treatment is brought to 38–42 mN/m for ink adhesion, measured by test inks per ISO 8296. Sports shoe components use injection-molded plates or foamed structures; Shore D 55 provides flexural modulus of 170 MPa and high rebound, but published data for fatigue crack growth in this specific component is limited.

Extrusion and Injection Molding Parameters for Shore D 55 PEBA

Single-screw extruders used for Vestamid E55-S3 are configured with a barrier screw, screen pack 80–120 mesh, and an L/D ratio of 24:1 to 30:1. Compression ratio is maintained at 2.5:1 to 3.5:1 because excessive shear heating causes localized melt temperatures above 250 °C, leading to chain scission and discoloration. Barrel temperature profiles for tube extrusion begin at 190–200 °C in the feed zone and rise to 220–230 °C at the die; melt temperature at the adapter is measured between 210 °C and 230 °C. For blown film, die temperature is 215–225 °C, blow-up ratio is 1.5:1 to 2.5:1, and frost-line height is set below 60 % of bubble height to control bubble stability. Injection molding of seals and sports components uses barrel temperatures of 220–250 °C, injection pressure 60–100 MPa, holding pressure 40–80 MPa, and mold temperatures of 20–60 °C. Screw back pressure is 0.5–1.5 MPa; clamp force is calculated from the projected area at a specific injection pressure of 0.5–0.8 t/cm². Gate freezing time should be determined empirically because the soft segment reduces thermal conductivity and extends solidification time relative to semicrystalline homopolymer nylon 12. Molding defects observed on production lines include jetting when injection speed is too high in thick seal sections, sink marks at rib intersections when holding pressure is below 40 MPa, and delamination when contaminated regrind contains polyolefin films. Mold release is generally not required for polished tool surfaces, but external lubricants containing silicone can interfere with post-molding corona treatment or adhesive bonding.

Comparison with other Vestamid E grades is required when a design changes hardness or flexural modulus. The Shore D value is not an isolated surface property; it reflects the mass fraction of nylon 12 hard segments and therefore influences tensile strength, creep, and permeation.

In contrast to thermoplastic polyurethane elastomers of similar Shore D 55, Vestamid E55-S3 has a density of 1.01 g/cm³ versus typical TPU densities of 1.10–1.25 g/cm³, and equilibrium moisture uptake of about 1.2 % versus higher values for some polyether TPUs. This reduces part weight and humidity-induced dimensional change. Compared with plasticized polyamide 12, the absence of external plasticizer prevents extraction in oil and fuel contact, but it also narrows the softening range compared with highly plasticized grades; the Vicat A50 softening temperature is approximately 150 °C.

When Low-Temperature Flexibility and Plasticizer-Free Stability Are Required

In cold-climate pneumatic and hydraulic installations, components are bent and impacted at temperatures below -20 °C during assembly. Notched Charpy impact testing per ISO 179-1/1eA is preferred over unnotched tests for quality control because the notch sharpness reveals brittle transition behavior. Typical PA12-based PEBA grades of Shore D 55 show no break at -40 °C, but the exact result depends on moisture conditioning to ISO 291 at 23 °C/50 % RH prior to testing. The polyether soft segment glass transition is below -60 °C, so rapid crack propagation resistance in thin-walled tubing is maintained under flexural fatigue. This is not a property that can be achieved reliably with external plasticizers because plasticizer migration into fuel, oil, or grease causes time-dependent embrittlement. For fuel vapor tubing, permeation testing per SAE J2659 or DIN EN ISO 20876 is required to determine wall thickness; alcohol-containing test fuels with high permeation aggressiveness require lot-specific validation. Published data for this specific configuration is limited for fuels containing more than 10 % methanol.

Operational boundaries include limited resistance to strong acids, chlorinated solvents, phenols, and continuous hot water above 80 °C; hydrolytic stability in aqueous oilfield or coolant media should be evaluated by ISO 23936 or ISO 24618 before production. The material is not inherently flame-retardant; UL 94 classification is not part of the standard specification. Because the grade is stabilized for heat and light, regrind from clean sprues and edge trims can typically be re-introduced at 20–30 % in non-critical applications, but the stabilizer concentration in regrind should be monitored by melt flow rate change per ISO 1133-1; deviations greater than 15 % from virgin MFR indicate excessive thermal history.