Medical
Medical grade polypropylene molding
Polypropylene is the default resin for a large share of medical disposables because it is cheap, chemically inert, and tolerates steam. This page covers what "medical grade" actually commits a resin producer to, homopolymer against copolymer, sterilization compatibility, and what we do and do not offer.
Mechanical figures for unfilled grades at 23 °C, reproduced from our polypropylene material page. Confirm against the specific medical grade's datasheet.
What "medical grade" commits to
There is no regulatory body that stamps a resin "medical grade" as a single pass or fail. What exists in practice is a named grade, natural or colored with an FDA-listed or biocompatibility-tested colorant, that the resin producer backs with a USP Class VI and/or ISO 10993 biological evaluation data package specific to that grade, and a certificate traceable to the production lot.
A drawing or a purchase order that says "medical grade PP" without naming the grade is not a specification a molder or a resin distributor can act on. Name the grade, and ask for the certificate against the lot that actually ran your parts, not a generic datasheet.
Homopolymer or copolymer
Both are run in medical service and the choice is set by sterilization method and service temperature, not by cost alone.
| Homopolymer PP | Copolymer PP | |
|---|---|---|
| Stiffness and HDT | Higher. The default for rigid labware and syringe barrels | Lower, trades stiffness for toughness |
| Low temperature impact | Brittle below roughly 0 °C | Retains impact strength well below 0 °C |
| Clarity | Hazier | Random copolymer grades run clearer, closer to natural clarity for fluid-level visibility |
| Typical medical use | Rigid labware, syringe barrels, diagnostic housings, autoclavable trays | Hinged caps and closures, blood collection tube components, anything stored or handled cold |
Where a part is both rigid and cold-handled, for example a sample tube that ships on ice, the datasheet's notched Izod at the actual service temperature settles the choice, not the room-temperature figure alone.
Sterilization compatibility, by method
| Method | How PP does |
|---|---|
| Steam autoclave, 121–134 °C | One of the more autoclave-tolerant common thermoplastics. Homopolymer's ~100 °C HDT sits close to the cycle temperature, and PP does not hydrolyse the way polycarbonate does under repeated steam. Confirm cycle count against the grade's datasheet; fillers and stabilizer packages shift the number. |
| Ethylene oxide | Runs well. PP does not absorb EtO to the degree some other polymers do, but the part still needs the standard degassing period before residuals clear to the limit the device requires. |
| Gamma irradiation | The one to watch. Unstabilized PP loses impact strength and yellows under gamma dose, sometimes not visibly until weeks after irradiation as chain scission continues. A gamma-stabilized grade, additised specifically for radiation resistance, is a different material selection from a standard homopolymer and should be named on the drawing if gamma is the sterilization method. |
| E-beam | Similar sensitivity to gamma, dose-dependent, at lower dose penetration. |
Decide the sterilization method before the grade is finalized. A part specified for EtO and later moved to gamma without revisiting the resin grade is a common and avoidable field failure.
Where PP is actually specified in medical devices
- Syringe barrels and plunger bodies, where clarity and rigidity are needed together
- Labware: petri dishes, sample tubes, pipette components, well plates
- Diagnostic instrument housings, where PP's near-zero water absorption keeps dimensions stable
- Single-use disposables and fluid-path components outside the sterile boundary
- Hinged closures on kits and cases, using PP's living-hinge fatigue life
- Drug delivery device housings, non-patient-contact structural components
Design and molding notes specific to medical PP
Shrinkage is high for a commodity resin, 1.3 to 1.8 percent, and continues moving for up to 24 hours after ejection, so critical dimensions are measured the next day, not straight off the press. On our own tooling PP sits in DIN 16742 group TG8, about ±0.52 mm at a 100 mm dimension under general tolerance; see the tolerances guide for how that compares across resins and what tightening a specific feature costs.
Wall sections of 1.0 to 3.0 mm are typical. PP flows well enough that thin walls are achievable, but thick sections sink badly under that shrinkage, which matters more on a part that also has to seal or index against a mating component.
Regrind is a validation question, not a cost question, on medical parts. A standard commercial run tolerates a modest, stated regrind fraction; a validated medical process typically runs on virgin resin only, per lot, unless the customer's own process validation explicitly permits a stated regrind percentage. State which regime applies at quote stage, since it changes both price and the traceability paperwork.
Standards that apply to the material
| Standard | What it covers |
|---|---|
| USP Class VI | A materials-level in vivo biological reactivity test. Applies to a named resin grade and lot, not to "polypropylene" as a family. |
| ISO 10993-1 | The device-level biological evaluation framework the material evidence feeds into. |
| ISO 10993-5 / -10 | Cytotoxicity and irritation/sensitization testing, commonly requested alongside Class VI for a device-level file. |
| USP <661.1> / <661.2> | Applies instead of Class VI where PP is used as primary pharmaceutical packaging rather than a device component; covers plastic materials of construction and the finished packaging system. |
Our status
Trumould runs polypropylene, including medical grades, on our in-house injection molding capability, and supplies material certificates traceable to grade and lot on request. We hold ISO 9001; we do not currently hold ISO 13485, and we say so plainly here rather than let a silence be read as a claim.
Trumould does not operate a classified cleanroom. Medical grade PP components that do not require a classified environment, such as external housings, labware, and non-sterile-fluid-path disposables, are within what we mold today. Parts in the sterile fluid path or requiring ISO 7 or ISO 8 classified molding are outside our current scope; see the cleanroom injection molding page for how that requirement is actually decided before you send a drawing.
What makes a polypropylene grade medical grade?
There is no single certification called medical grade PP. What exists is a named resin grade, natural or coloured with an FDA-listed or biocompatibility-tested colorant, supplied by the resin producer with a USP Class VI and/or ISO 10993 biological evaluation data package tied to that grade, and traceable to the lot it was made from. A polymer family claim without a grade and a certificate is not a specification, on PP or on any other material.
Should medical PP parts be homopolymer or copolymer?
Homopolymer PP has the higher heat deflection temperature and is the default for parts that see steam autoclave, such as rigid labware and syringe barrels. Copolymer PP trades some stiffness for impact and low temperature toughness, which is why it is more common on hinged closures, caps, and anything stored or handled cold. The choice is set by the sterilization method and the service temperature, not by cost alone.
Can polypropylene be steam autoclaved?
Yes, PP homopolymer is one of the more autoclave-tolerant common thermoplastics because its heat deflection temperature, about 100 degrees C at 0.45 MPa, sits close to the 121 to 134 degree C autoclave range, and it does not hydrolyse the way polycarbonate does under repeated steam exposure. Confirm the cycle count and temperature against the specific grade's datasheet, since fillers and stabiliser packages shift the number.
Does Trumould mold in a cleanroom for medical PP parts?
No. Trumould does not operate a classified cleanroom. Medical grade PP components that do not require a classified environment, such as external housings, labware, and non-sterile-fluid-path disposables, are within scope. Parts in the sterile fluid path or requiring ISO 7 or ISO 8 classified molding are outside what we currently offer; see the cleanroom injection molding page for how that requirement is actually decided.
More
Related guides
Polypropylene material page
General PP properties, grades, and design notes across all industries.
Medical injection molding
Standards, materials, documentation, and sterilization across all resins we run.
Cleanroom injection molding
When a device actually needs a classified environment, and what Trumould does not offer.
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