6 min read · · CleanCut team
Coated vs. uncoated Tyvek®: choosing the right lidding for rigid trays
A rigid tray is only as good as its lid. Heat-seal coated Tyvek® bonds to the tray flange and peels open cleanly. Uncoated Tyvek® does not seal to a tray on its own, but it still has a place in the package. Here is how to choose.
A thermoformed tray holds and protects the device. The lid turns that tray into a sterile barrier. It has to bond to the tray flange and hold through sterilization, shipping and storage. Then it has to peel open cleanly at the point of use, without tearing or leaving fibers behind.
Tyvek® is the usual lid material for rigid medical trays. It is strong, puncture resistant and breathable. But it comes coated and uncoated, and that difference decides whether it can seal to a tray at all. This article explains what the coating does, where each format fits, and what to check before a design goes into validation.
What a heat-seal coating does
Tyvek® is a nonwoven web. Its fine fibers form a winding path that lets air and sterilant gases through while holding back microorganisms. That is why it works on packages sterilized with ethylene oxide (EtO), where gas must reach the device and then leave again.
Uncoated Tyvek® has no adhesive layer. It bonds to flexible films that carry a compatible sealant layer, which is how many pouches are built. Rigid tray resins are different. They do not bond to uncoated Tyvek® in a controlled, peelable way.
A heat-seal coating solves this. It is a thin adhesive layer on one face of the web. Under the right temperature, pressure and dwell time, the coating bonds to the tray flange. When the user pulls the lid, the bond releases at the coating. The Tyvek® itself stays intact.
Why pattern coatings matter
On medical lidding, the coating is usually applied in a pattern rather than as a solid layer. The uncoated spaces in the pattern keep the web breathable, so EtO can still pass through the lid. The pattern also gives a clean, visible peel. After opening, the sealed area is easy to see on the flange, which makes seal inspection simpler.
Coated vs. uncoated at a glance
| Property | Coated Tyvek® | Uncoated Tyvek® |
|---|---|---|
| Heat-seal layer | Yes, pattern-applied on one face | None |
| Seals to rigid trays | Yes: PETG, PVC, HDPE, HIPS, PP, with a matched coating | Not on its own |
| Breathability | Kept by the pattern coating | Full web breathability |
| Peel | Clean, visible peel from the flange | Not used for tray seals |
| Formats from CleanCut | Die-cut lids (1073B), rollstock (1073B, 2FS) | Die-cut sheets in custom shapes |
| Typical uses | Rigid tray and blister lidding, pouch stock | Covers, interleaves and layers that do not seal to a tray |
The short version: if the Tyvek® has to seal to a rigid tray, it needs a heat-seal coating. If the part does not seal to anything, or it seals to a film that carries its own sealant, uncoated may be the better choice.
Choosing a grade: 1073B or 2FS
Coated Tyvek® lidding is most often specified in one of two medical grades.
1073B is the heaviest and strongest medical Tyvek® grade. Choose it for heavy devices, sharp edges and corners, and dense kits. Orthopedic implants and surgical instrument sets are typical examples. Our coated Tyvek® die-cut lids are cut from heat-seal coated 1073B for this reason.
2FS is lighter. It costs less and suits lighter devices and high-speed form-fill-seal lines.
If you are unsure, start from the device. Its weight, its sharp features, and how far it can move inside the tray during shipping all point toward one grade or the other. Distribution testing, commonly to ASTM D4169 or an ISTA procedure, confirms the choice, along with aging to ASTM F1980 and real-time aging data. A lighter grade that passes is a real saving. A lighter grade that fails costs you a test cycle.
Matching the lid to the tray
Heat-seal coated Tyvek® seals to the common rigid tray materials when the coating suits the tray resin. Each resin behaves a little differently, so qualify the lid, the tray and the sealing window together. Our die-cut lids use a standard coating for PETG, PVC and HIPS trays, and a polyolefin-specific coating for HDPE and PP trays, which are often the hardest to seal well.
| Tray material | Clarity | Notes for lidding |
|---|---|---|
| PETG | Clear | The most common medical tray resin. Tough, forms well, shows the device. |
| PVC | Clear | Economical and easy to form. Some grades can discolor after gamma; check with your tray supplier. |
| HDPE | Translucent to opaque | Tough and chemical resistant. |
| HIPS | Opaque | Economical and rigid. Often used for inner trays and less demanding devices. |
| PP | Translucent | Chemical resistant. Specify a radiation-stabilized grade if the package will see gamma. |
A few practical checks before you freeze the design:
- Flange. A flat, wide, consistent flange gives the coating a good surface to bond to. Generous corner radii help the tray form evenly and keep the seal consistent.
- Lid outline. The lid should cover the full seal area and leave room for a peel corner or tab.
- Peel tab. A tabbed lid gives gloved hands a clear place to start. Put the tab at the corner the user reaches first.
- Print. Lids can be printed or unprinted. Decide early, because print position depends on the final outline.
- Sealing window. Temperature, pressure and dwell time are set on your sealer and proven in process validation under ISO 11607-2. Seal strength is commonly tested to ASTM F88, seal integrity with methods such as ASTM F1929 dye penetration or ASTM F2096 bubble leak, and seals are inspected visually to ASTM F1886.
Die-cut lids or rollstock?
Coated Tyvek® comes in two formats. The choice follows your sealing equipment.
Die-cut lids are cut to the tray outline and delivered as eaches. They suit tray sealers that load one lid per cycle, and they suit prototypes, pilot builds and moderate production volumes. The tab and outline are cut in before the lid reaches your line. We cut these in our ISO Class 8 cleanroom in Kensington, Prince Edward Island.
Rollstock feeds automated form-fill-seal lines that form the tray, load the device, seal the lid and cut the package in one pass. We supply coated Tyvek® rollstock in 1073B at 86 gsm and 2FS at 71 gsm (weights include the coating), sourced from qualified manufacturers.
Many programs use both. Die-cut lids carry the design through prototypes and early builds. Rollstock takes over when volume justifies a form-fill-seal line. If you plan that move, keep the same grade and coating so your material data carries forward. The new sealing process still needs its own validation.
Where uncoated Tyvek® fits
Uncoated Tyvek® still earns a place in a sterile barrier system. It keeps the full strength and breathability of the web, and it cuts to clean, precise shapes.
We cut uncoated Tyvek® sheets in custom shapes with rounded corners, up to 30 × 30 in (762 × 762 mm). Typical uses include breathable dust covers, interleaves between devices, and protective layers in trays and kits, where the part does not need to seal to a rigid surface.
Sterilization
Coated Tyvek® lids are compatible with EtO, gamma and e-beam. The pattern coating keeps the lid breathable for EtO. For steam, Tyvek® is limited to restricted, lower-temperature cycles (up to 127 °C), so ask us before you design around it.
Compatibility always depends on grade, coating and your process. Validate the complete package in your own sterilization cycle. Remember that the lid is a component. Your finished sterile barrier system, meaning the tray, the lid and the seal together, is what the device maker, or its contract manufacturer, validates to ISO 11607-1 and -2.
Next steps
Send us your tray spec or a sample tray, the device weight and your sterilization method. We will suggest a lid outline and tab position, then cut prototype lids for your sealing trials. Small quantities are fine.
Check each material against your cycle in the sterilization compatibility matrix, then request lid samples or a quote.