VESTAMID® Care ME47 is a polyamide 12-based thermoplastic elastomer supplied by Evonik Operations GmbH for medical device applications in which tubing, catheter shafts, and repeated-sterilization components require a combination of low flexural modulus and low extractable content. The grade designation encodes a nominal hardness of 47 Shore D measured according to ISO 868. The polymer is classified within the VESTAMID Care portfolio as a ready-to-process compound without external plasticizers, halogenated flame retardants, or heavy-metal stabilizers. Biocompatibility documentation is structured around ISO 10993-1 endpoint evaluation for surface-contacting and externally communicating devices, with additional testing under USP <88> Class VI protocols. The material is supplied in pellet form and is intended for conversion by single-screw extrusion or injection molding.

In catheter shaft extrusion, the primary processing challenge is not melt temperature alone but residual moisture control. Polyamide 12 absorbs water at lower rates than polyamide 6 or 66, yet equilibrium moisture in humid air is sufficient to hydrolyze the resin during plastication. Production-scale tubing lines using a 30 mm single-screw extruder with L/D 25 and a three-zone screw have shown ovality fluctuation and melt-pressure instability when pellet moisture exceeds 0.10% as measured by Karl Fischer titration. Pre-drying at 80°C for 4–6 h in a dehumidifying hopper dryer with a dew point of at least −40°C reduces residual moisture below 0.10% and restores stable melt pressure at 210–230°C barrel set temperatures. Thin-wall tube profiles are typically calibrated in vacuum water tanks maintained at 20–40°C to freeze surface orientation before downstream cutting or winding.

Why Does the Soft-Segment Architecture Distinguish ME47 from Rigid Polyamide 12?

The Shore D 47 hardness of VESTAMID Care ME47 places it between flexible polyamide 12 elastomer grades with Shore D < 40 and rigid unmodified polyamide 12 grades that commonly measure 70–75 Shore D. The lower hardness is achieved without external plasticizer. In unmodified PA12, the flexural modulus is typically in the range 1200–1500 MPa under ISO 178; the elastomeric grade reduces flexural modulus to approximately 350–450 MPa, allowing catheter shafts to track tortuous anatomy without kinking. The polyamide 12 segment retains acid and base resistance relative to thermoplastic polyurethanes, while the soft segment contributes low-temperature impact resistance. Unlike plasticized PVC, which relies on 20–40 wt% monomeric or polymeric plasticizer, the flexibility of VESTAMID Care ME47 is inherent and does not generate plasticizer migration into lipid-containing media. The trade-off is a lower tensile modulus and a lower continuous-use temperature ceiling than semi-crystalline polyamide 12 homopolymer; published data for this specific configuration is limited in high-pressure balloon applications.

Tensile modulus, moisture uptake, and melt volume rate benchmarks

Representative values for VESTAMID Care ME47 are summarized in the table below. The exact certificate of analysis for a given lot should be consulted, because melt volume rate and tensile values vary with moisture content and thermal history. All mechanical values are measured on dry-as-molded specimens conditioned at 23°C/50% RH for 48 h unless otherwise stated.

Compared with polyamide 6 and 66, the polyamide 12 backbone reduces equilibrium water uptake and therefore reduces post-molding dimensional change in humid hospital environments. The <1.5% saturation value under ISO 62 is lower than the 8–9% saturation uptake typical of unmodified polyamide 6. The lower moisture affinity also means that drying is less energy-intensive than for polyamide 6, but pre-drying remains mandatory because the melt-processing window is narrower for the elastomeric grade than for high-viscosity polyamide 12 extrusion resins.

The melting range of 170–176°C places the material below polyamide 6 and polyamide 66 processing temperatures, reducing cooling time in thin-wall extrusion. The melt volume rate range of 4–12 cm³/10 min makes it a medium-viscosity grade; tube profiles below 0.50 mm wall thickness may require a low-shear screw geometry to avoid melt fracture. The processing window is narrower than for rigid polyamide 12 because soft-segment degradation accelerates above 240°C. The recommended maximum melt residence time is <10 min, and barrel zones should be staged from 200°C at the feed throat to 225°C at the die. Published capillary rheometry data for this specific grade is limited; shear viscosity should be established with the incoming lot under ISO 11443 using a dry nitrogen purge.

Twin-screw compounding is not required because the supplier delivers a fully formulated compound. For direct conversion, single-screw extruders with L/D 24–30, compression ratio 2.5:1–3.0:1, and a barrier or Maddock section are typical for stable melt temperature. Grooved-feed extruders can generate excessive melt temperature and are not recommended for thin-wall tubing unless screw speed is reduced and a melt pump is installed. In production, melt pumps damp pressure pulsation and permit wall thickness tolerances of ±0.02 mm on 1.0 mm outer-diameter catheter shafts when combined with closed-loop vacuum sizing and laser gauging. The melt pump inlet pressure should be maintained between 50–80 bar to avoid cavitation; specific values depend on throughput and die resistance.

In practice, the material is selected for catheter lumens and sheaths that contact lipid emulsions, contrast media, or sterilizing agents because it does not contain phthalate-type plasticizers. However, selection must account for the specific drug formulation. Published data for this specific configuration is limited for long-term infusion of chemotherapeutic agents; extractables studies following ISO 10993-18 are required for the finished device. The grade should not be combined with strong oxidizing acids at elevated temperature, and it is not recommended for continuous exposure to steam above 121°C because repeated autoclaving may induce dimensional growth from moisture absorption. These boundaries are derived from general polyamide 12 chemistry and should be confirmed through finished-device performance qualification.

When Finished Devices Are Exposed to Gamma, Ethylene Oxide, or Electron-Beam Sterilization

VESTAMID Care ME47 is used in single-use devices that are terminally sterilized by gamma radiation at typical doses of 25–40 kGy, by ethylene oxide under ISO 11135, or by electron beam at surface doses not exceeding 50 kGy. Gamma and electron-beam exposure can produce free radicals that recombine into crosslinks or oxidative species; the net effect on a 47 Shore D elastomer is typically a small increase in gel content and a measurable reduction in elongation at break. Radiation-induced embrittlement is dose-rate and oxygen dependent; vacuum-sealed trays reduce oxidative degradation compared with air-permeable pouches. For ethylene oxide cycles, the low water uptake of the polyamide 12 backbone limits residual ethylene oxide uptake, but the finished device must still be aerated according to ISO 10993-7 residual limits.

Steam sterilization is not the default processing route. Polyamide 12 elastomers can survive a limited number of 121°C cycles, but the combination of absorbed moisture and heat lowers the glass transition of the soft segment and can cause tubing ovality or lumen collapse. If steam is required, tubes should be dried and supported on mandrels to prevent deformation. For high-energy radiation, the maximum validated dose should be established by plotting post-sterilization tensile elongation and burst pressure against dose; lot-to-lot variation in stabilizer content can shift the threshold by 5–10 kGy. Published data for this specific configuration is limited at doses above 50 kGy.

For injection molding of hubs, luer fittings, and connectors, melt temperatures of 220–240°C and mold temperatures of 40–80°C are typical. Hot-runner systems should be designed with low-shear geometry and no dead spots, because the elastomeric grade has a lower viscosity than rigid polyamide 12 and can drool from open nozzles. Clamp force requirements are moderate; thin-wall connectors with projected areas below 100 cm² have been molded on machines with 500–1000 kN clamp force, but this is tool-dependent. The use of nucleated or fast-cycle grades is not necessary because the polyamide 12 backbone crystallizes rapidly; ejection can be performed when the part surface temperature falls below 80°C. Amine-based color concentrates should be avoided because their basic decomposition products can promote polyamide degradation and shift melt viscosity. Only medical-grade masterbatch carriers approved for polyamide 12 should be used.

Post-extrusion annealing at 80–100°C for 2–4 h under nitrogen can stabilize the soft-segment orientation and reduce subsequent shrinkage after gamma irradiation. Annealing is particularly relevant for braided catheter shafts, where the inner liner and outer jacket are coextruded and then reinforced with stainless-steel wire. The difference in thermal expansion between the metal braid and the polyamide 12 elastomer can produce residual stress; annealing relieves these stresses before sterilization. Unannealed tube spools may exhibit length shrinkage of 1–3% after EtO aeration; the exact shrinkage is a function of draw-down ratio and cooling rate. Process validation should include dimensional checks after sterilization and 24 h conditioning at 23°C/50% RH.

The material is supplied under a change-control policy for medical device components, meaning that monomer source, catalyst residues, and antioxidant package are not changed without customer notification. The grade is manufactured to a defined specification for viscosity, color, and extractables. Batch release documentation includes melt volume rate per ISO 1133-1, moisture content per ISO 15512, and visual contamination. For devices marketed in the European Union, the finished supplier declaration covers REACH registration and restriction obligations; for electrical device components, the formulation is designed to support RoHS heavy-metal limits. These regulatory statements apply to the raw material as delivered, not to the sterile finished device.

The comparative table shows the central selection trade-off: VESTAMID Care ME47 provides inherent flexibility without plasticizer migration and with lower moisture uptake than polyamide 6, but it does not match the optical clarity of some polyurethane or PVC formulations. If transparent tubing is required, the material must be validated for haze and light transmission under the relevant device specification, because the polyamide 12 backbone is translucent rather than water-clear. In applications where clear visibility of the fluid path is a strict requirement, a different VESTAMID Care grade or a multilayer construction with a clear outer layer may be necessary. Published data for this specific configuration is limited with respect to visible light transmission and yellowness index after gamma sterilization; lot-specific yellowness index should be measured according to ISO 13468-2 or DIN 6167.

Relative to PA12 homopolymers, the ME47 grade has lower hardness and flexural modulus, but it also has lower tensile strength and lower creep resistance. This makes it suitable for dynamic flexing components but not for load-bearing connectors that require high thread strength. For luer hubs, glass-filled or rigid polyamide grades are preferred; overmolding a flexible ME47 jacket onto a rigid hub is common in catheter manufacturing. The melt adhesion to unmodified polyamide 12 is generally strong because both share the same hard-segment chemistry, but coextrusion tie layers should still be selected with melt viscosity ratios below 3:1 to avoid interfacial instability. The low-temperature impact resistance of the elastomeric grade is better than unmodified PA12; brittle failure at −40°C is less likely, but the exact ductile-to-brittle transition depends on moisture content.

Relative to polyether block amide products with similar Shore D hardness, the designation ME47 is differentiated by its polyamide 12 hard segment, which provides lower equilibrium water uptake than polyamide 6/polyether block amides and better retention of flexural modulus after EtO humidification. Relative to plasticized PVC, the absence of plasticizer migration removes a failure mode in lipid-containing fluid paths, but the material has a higher melt processing temperature and cannot be solvent-bonded with cyclohexanone-based PVC adhesives; polyamide-compatible adhesives or thermal bonding are required. Relative to unmodified polyamide 12, the elastomeric grade sacrifices tensile modulus and abrasion resistance for kink resistance and cyclic flexural fatigue performance. In bench tests of catheter shaft materials, flexural fatigue is usually evaluated under repeated bending to 180° at body temperature, but the specific fatigue limit depends on wall thickness and hydration state.

When the grade is used in multi-lumen catheter shafts, the low saturation water uptake reduces post-sterilization ovality compared with polyamide 6, but the die and tip design must compensate for die swell differences between the elastomeric grade and rigid polyamide tie layers. Post-conditioning dimensional checks should be performed at 23°C/50% RH to ISO 291 or the relevant device standard, and burst pressure testing should follow ISO 10555-3 for intravascular catheter shafts. The final processing parameters—screw speed, draw-down ratio, vacuum level, and cooling water temperature—must be locked during design transfer, because the soft-segment orientation generated in the calibration tank directly influences kink resistance and column strength.