Material selection is one of the most consequential decisions in medical device injection molding. The wrong material means a part that fails biocompatibility testing, discolors with sterilization, or becomes brittle in contact with the drugs it's supposed to deliver. This guide covers the most common medical-grade plastics and how to choose between them.
What "Medical-Grade" Actually Means
A medical-grade plastic is not a specific material — it is a designation applied to a material that has been tested and certified to meet medical device regulatory standards. The key standards are:
- USP Class VI: US Pharmacopeia biological reactivity tests — the most commonly required standard for non-implantable medical devices. Tests include systemic injection, intracutaneous injection, and implantation.
- ISO 10993: Biological evaluation of medical devices — the international standard covering a broader range of biocompatibility tests including cytotoxicity, sensitization, and systemic toxicity.
- REACH / RoHS compliance: Required for devices sold in EU markets — restricts hazardous substances including certain plasticizers and flame retardants.
When we say "medical-grade polycarbonate," we mean a PC formulation from a material supplier that has conducted USP Class VI or ISO 10993 testing and can provide documentation. The same base polymer in a non-medical grade may not have this certification and should not be used in medical devices.
Polycarbonate (PC) — The Default for Stopcocks and Manifolds
Medical-grade PC is the most common material for injection molded IV therapy components — stopcocks, manifolds, connectors, and anything where visual inspection of fluid flow is required.
| Property | Value | Implication |
|---|---|---|
| Clarity | High optical clarity | Air bubble and flow visualization |
| Impact resistance | Very high | Does not shatter if dropped |
| Sterilization | EO compatible; gamma causes yellowing | EO preferred for IV components |
| Chemical resistance | Good (not for strong solvents) | Compatible with common drugs and saline |
| Biocompatibility | USP Class VI | Suitable for fluid contact |
Best for: 3-way stopcocks, IV manifolds, contrast injection fittings, Luer connectors, any component where visual inspection of fluid flow matters.
ABS — Structural Parts and Housings
ABS offers good rigidity, impact resistance, and an excellent surface finish for cosmetic parts. It does not have the optical clarity of PC, making it unsuitable for fluid-contact components where visualization is needed.
Medical-grade ABS is used for stopcock handles, device housings, and structural components that do not contact fluids directly. Its excellent moldability produces crisp, dimensionally accurate parts with good surface finish.
Best for: Device housings, stopcock handles, structural brackets, color-coded components, non-fluid-contact parts.
Polypropylene (PP) — Chemical Resistance and Autoclaving
PP offers superior chemical resistance compared to PC and ABS, and is the only common medical plastic that can be autoclaved (steam sterilized at 121°C). This makes it the material of choice for reusable components and components in contact with aggressive chemicals.
PP is semi-crystalline, which gives it better fatigue resistance than amorphous plastics but somewhat worse impact resistance at low temperatures. It has good living hinge properties — PP hinges can flex millions of times without cracking.
Best for: Reusable components, autoclave-compatible parts, chemical-resistant fittings, containers, components in contact with organic solvents or concentrated acids.
PEEK — High-Performance Applications
PEEK (polyether ether ketone) is in a different class from the plastics above. It maintains mechanical properties at temperatures up to 250°C, has exceptional chemical resistance, and can be sterilized by any method. It is FDA-approved for implantable devices.
PEEK costs 10–20× more than PC and requires higher injection molding temperatures and pressures. It is used only when the application genuinely requires its performance — surgical instrument handles, catheter components in contact with body fluids, and parts that must survive repeated autoclave cycles.
Sterilization Compatibility — the Table That Decides the Material
Material selection for an IV component is usually settled not by strength but by how the finished device will be sterilized. The three common routes make different demands: steam autoclaving runs at 121 °C or 134 °C under pressure, ethylene oxide (EtO) works near 37–63 °C, and gamma irradiation delivers a typical 25–40 kGy dose at room temperature. A resin that is perfect for one route fails another:
| Material | Autoclave 121 °C | Autoclave 134 °C | EtO | Gamma 25–40 kGy |
|---|---|---|---|---|
| Polycarbonate (PC) | No — heat deflection ≈135 °C, parts warp and craze | No | Yes — the standard route | Yes, but unstabilized PC yellows; gamma-stabilized grades hold clarity |
| ABS | No — softens from ≈95 °C | No | Yes | Yes, slight darkening |
| Polypropylene (PP) | Yes — melting point 160–165 °C | Marginal — repeated 134 °C cycles distort thin walls | Yes | Risky — gamma embrittles standard PP; radiation-stabilized grades exist and must be specified |
| PEEK | Yes, indefinitely — continuous service ≈240 °C | Yes | Yes | Yes |
| TPE / TPU (soft parts) | Grade-dependent, mostly no | No | Yes | Yes, grade-dependent |
Two traps account for most re-sourcing we see. Gamma on polycarbonate: the standard dose turns unstabilized PC visibly yellow — the part works, but a clinician reads yellow as degraded, so gamma-stabilized PC is the correct call whenever irradiation is the sterilization route. Gamma on polypropylene: standard PP loses impact strength progressively after irradiation and can shed brittle fragments months later; if a PP component will be gamma-sterilized, the radiation-stabilized grade is not optional. Both are resin-grade decisions that cost nothing at molding time and cannot be fixed afterwards.
A third, clinical one: lipid emulsions stress-crack standard PC. Stopcocks running TPN or propofol lines craze at the luer threads under the combination of stress and lipid contact — the reason lipid-resistant PC copolymers exist. If your device sees lipids, that belongs on the specification line, not in the complaint file.
On the phrase “medical-grade” itself: it is not a certification we or anyone can stamp on a finished part. It means the resin maker supplies that grade with biocompatibility data — ISO 10993 test reports or a USP Class VI listing — plus lot traceability and a no-change notification agreement. You specify the grade; the molder’s job is to mold that grade and only that grade, with the lot number on the paperwork.
Material Selection Summary
| If you need... | Choose |
|---|---|
| Fluid visualization (clear body) | Polycarbonate (PC) |
| Structural housing, colored part | ABS |
| Autoclave sterilization | Polypropylene (PP) |
| Chemical resistance (solvents, acids) | PP or PEEK |
| Implant-adjacent, highest performance | PEEK |
| Soft-touch, flexible seal | TPE / TPU |
Not sure which material to specify? Email your application requirements to [email protected]. Our engineers will recommend the appropriate medical-grade material based on your sterilization method, fluid contact requirements, and regulatory market. Material selection advice is included with every OEM quote.
Frequently Asked Questions
No. PC's heat-deflection temperature is around 135 °C, so a 121 °C steam cycle already warps and crazes the part, and 134 °C is out of the question. Autoclavable components are molded in polypropylene, which melts at 160–165 °C, or PEEK for repeated high-temperature cycles. PC devices are sterilized with EtO, or by gamma using a gamma-stabilized grade.
At the typical 25–40 kGy dose: ABS, PEEK and most TPEs pass; polycarbonate passes but yellows unless a gamma-stabilized grade is used; standard polypropylene is the one to watch — it embrittles after irradiation, so a radiation-stabilized PP grade has to be specified whenever gamma is the route.
It is a property of the resin grade, not a stamp on the finished part: the resin maker supplies biocompatibility data for that grade — ISO 10993 test reports or a USP Class VI listing — together with lot traceability and an agreement to notify before changing the formulation. Specifying the trade name and grade on the drawing is what makes a part medical-grade; molding it in "equivalent" resin is what silently un-makes it.
Standard polycarbonate stress-cracks in contact with lipid emulsions: the combination of molded-in stress at the luer threads and lipid exposure produces crazing over hours to days. Lipid-resistant PC copolymers exist for exactly this duty, and the fix is a grade change on the specification, not a process change at the molder.
Yes — that is the normal medical order. You name the trade name and grade, the partner facility molds that grade with the lot number documented, and no substitution is made without written approval. Quotes for medical components are returned within 48 hours.
Custom Medical Components Molded in Your Specified Material
Knowing that a stopcock body should be polycarbonate or that an autoclavable housing wants polypropylene is only half the job — you still need someone to mould the part. That is what we do. EKINSUN produces custom and OEM medical plastic components — three-way stopcocks, IV manifolds, luer connectors, contrast fittings, catheter hubs and custom housings — in exactly the medical-grade resin your application calls for: PC, ABS, PP, PEEK or a TPE over-mould.
You do not need a finished CAD model to start. Send a drawing, a physical sample, or even a hand sketch with the bore sizes and connection types, and our engineers reconstruct the geometry, recommend the resin from the table above, and quote tooling plus unit price. Low-volume and bridge-production runs are welcome — there is no obligation to commit to a high-MOQ injection-moulding contract to get a usable medical part made.
Material certificates, NDA before design review, and a 48-hour quote turnaround come as standard. See our custom medical injection-molding service, or browse moulded parts like the 3-way stopcock and IV manifold we make to spec.
