A fair number of skincare products these days contain vitamin C, retinol, hyaluronic acid, and the like. These are all active compounds, sensitive to oxygen, moisture, and/or light. The same is true for pharmaceutical ointments, which almost always contain sensitive formulas. In cases like this, simple LDPE/HDPE tubes do not suffice.

CO-EX barrier tubes combine multiple polymer layers to provide properties that a single polymer structure does not deliver on its own. When a formulation is sensitive to oxygen, moisture, or other environmental factors, having an EVOH-containing barrier layer for the plastic tube becomes a must.

However, it would be misleading to claim EVOH simply prevents oxidation on its own. It reduces oxygen transmission through the tube wall, but the finished product still depends on formulation stability and manufacturing consistency.

Key Takeaways

• CO-EX tubes combine several polymer layers to deliver properties a single layer cannot.
• EVOH provides a strong oxygen barrier, but its performance depends on humidity and construction.
• Barrier data compares films under lab conditions, not the finished tube’s real performance.
• Pharmaceutical use adds extractables, leachables, and closure integrity to the checklist.
• A simple decision tree can show whether a formula actually needs CO-EX or not.

What Are CO-EX Barrier Tubes?

Co-extrusion combines several material layers into a single tube wall during manufacturing. Each layer plays a role: structural layers give the tube its shape and squeeze behaviour, and a functional layer provides the protective barrier.

A typical construction pairs LDPE with a barrier layer, plus additional structural or functional layers. Tie or adhesive layers get added where needed to bond materials that would not otherwise stick together.

The number of layers varies by supplier as well as application. Some products require a 5-layer EVOH tube. For others, a 3-layer EVOH works fine. Additionally, more layers do not automatically mean better performance. What matters is whether the combination suits the specific formulation being packaged.

Why Does Oxygen Barrier Matter

Oxygen exposure drives colour change, odour change, and active ingredient degradation in many formulations. For products built around antioxidants or actives, this can shorten the effective shelf life well before the labelled expiry date.

Kuraray’s published EVAL data compares oxygen transmission for 20 micron films at 20°C and 65% relative humidity. LDPE shows around 10,000 cc per day per square metre, against around 1 cc for EVOH under the same conditions.

These values describe material barrier performance under defined lab conditions. They should not be presented as the oxygen transmission rate of a finished, filled tube in real storage conditions.

Real shelf conditions vary far more than a lab test does. Temperature swings, humidity, and storage duration all affect how much protection a barrier layer actually delivers over a product’s lifetime.

Why EVOH Is Used in Plastic Barrier Packaging

EVOH offers very high gas-barrier capability from a thin functional layer, which keeps the overall tube wall manageable while still meaningfully reducing oxygen transmission. This barrier performance can be influenced by humidity, since EVOH behaves differently in humid conditions than in dry ones. 

This is why actual tube construction and testing matter more than a single film data sheet. It is also why manufacturers position EVOH between protective structural layers in most tube designs. Doing so shields the barrier layer from direct moisture exposure and keeps its performance more consistent.

CO-EX Tubes for Cosmetics

Active skincare, antioxidant formulations, sensitive creams, and treatment products are common candidates for CO-EX EVOH tubes. These products have demanding shelf-life requirements and benefit from the added oxygen protection.

Even with a barrier tube in place, formulation compatibility and stability testing remain necessary. A barrier layer reduces one variable; it does not remove the need to test the finished product.

Vitamin C serums, retinol-based treatments, and certain natural oil blends are common examples. Brands have found CO-EX construction worth the added cost for these, based on their own stability data.

CO-EX Tubes for Pharmaceuticals

Topical creams, ointments, gels, and other dermatological and OTC products often carry stricter packaging requirements than cosmetics, given their regulatory status and intended use.

USP <661> covers plastic packaging systems and materials used for pharmaceuticals, biologics, and dietary supplements. The document includes standards for materials such as HDPE and LDPE. ISO 15378:2017 addresses primary packaging materials for medicinal products specifically, and folds GMP requirements into the quality management system a supplier operates under.

Buyers sourcing packaging for OTC products should ask suppliers directly whether they manufacture under a system aligned with ISO 15378. Do not assume general cosmetic-grade production is equivalent.

Why Barrier Protection Is Just One Part of Plastic Tube Packaging 

Extractables, leachables, chemical compatibility, migration, closure integrity, seal quality, and dimensional consistency all sit alongside barrier performance in a complete packaging evaluation.

USP explains that extractables and leachables can originate from packaging systems and potentially affect drug potency, stability, safety, and effectiveness. That makes packaging testing a formulation question, not just a materials one.

How to Decide Whether You Need CO-EX EVOH Tubes

Ask the following questions:

• Does the formulation require enhanced oxygen protection? 

If yes, CO-EX/EVOH is worth investigating.

• Is the formula already stable in standard PE packaging? 

If yes, monolayer LDPE or HDPE may be sufficient, and CO-EX may add cost without a real benefit.

• Is the product pharmaceutical or OTC? 

If so, appropriate compatibility and stability assessment should guide the decision, not assumptions about barrier tubes being automatically required.

• Does the destination market impose additional requirements? 

Review the applicable regulatory framework before finalising a barrier structure, since expectations vary between the UK, EU and other export markets.

These questions form the basics that guide the procurement decision.

What Buyers Should Request From a CO-EX Tube Manufacturer

When evaluating CO-EX plastic tubes, be sure to ask about the following:

• Layer structure
• Material specifications
• Barrier test data
• Compatibility information
• Batch traceability
• Certificate of Analysis
• Samples
• Stability testing support
• Production consistency

CO-EX is not simply a premium material choice for brands that want to look thorough. It is a functional packaging decision, driven by how sensitive a formulation actually is and how much protection it genuinely needs.

Common Misconceptions About Barrier Tubes

One common assumption is that a barrier tube fixes an unstable formula. It does not. If a formula already breaks down through some other pathway, better packaging alone will not solve that on its own.

Another assumption is that thicker tube walls always mean stronger barrier performance. Wall thickness affects rigidity and squeeze feel more than it affects gas transmission, which depends mainly on the barrier layer itself.

A third misconception treats CO-EX as a fixed, one-size-fits-all specification. Layer count, layer order, and material ratios can all be adjusted. A supplier should be able to explain why a given structure was chosen for a specific brief.

How to Test a CO-EX Structure Before Committing

Stability testing on the actual formula, in the actual tube, remains the only reliable way to confirm a barrier structure performs as expected. Lab film data is a starting point, not a substitute.

Accelerated stability testing under elevated temperature and humidity can flag problems faster than real-time storage trials, though real-time data still matters for confirming long-term claims.

Brands should also test the closure and seal alongside the barrier layer. A strong barrier tube with a poor seal can still let in more oxygen than expected, undermining the investment in the multi-layer wall.

Wrapping Up: Sourcing Considerations for CO-EX Plastic Tubes

CO-EX tubes generally cost more per unit than monolayer alternatives, driven by additional resin, tooling complexity, and slower production speeds compared with single-layer extrusion. Buyers should ask suppliers to quote both a monolayer and a CO-EX option side by side, where feasible. 

For brands running multiple SKUs, it can make sense to reserve CO-EX construction for the products that genuinely need it. Standardising the entire range on the pricier structure by default rarely pays off.

For brands unsure whether their formula needs a barrier structure, Sitons Propack can review the sensitivity profile and suggest a construction to test.

Frequently Asked Questions

Does an EVOH barrier automatically increase a product’s shelf life?

No. Shelf life depends on formulation stability, preservatives, manufacturing conditions, packaging compatibility, storage conditions, and distribution exposure. EVOH can strengthen oxygen-barrier performance, but the finished product still needs proper stability evaluation.

Can CO-EX tubes be recycled?

Recyclability depends on the complete packaging structure, layer composition, closures, local collection systems, and applicable assessment methodology. Multi-layer construction should be evaluated against the destination market rather than labelled recyclable by default.

Is EVOH suitable for every pharmaceutical formulation?

No. Pharmaceutical packaging must be selected according to the specific formulation, route of administration, stability requirements, and regulatory expectations. Compatibility, extractables, and leachables should be evaluated for each product.

How should a buyer compare two CO-EX tube suppliers?

Compare their complete technical documentation rather than just the stated number of layers. Look at material specifications, barrier data, quality controls, traceability, sampling, and their ability to support formulation-specific testing.