Medical-Grade Plastics for Injection Molding — PC vs ABS vs PP

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.

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