Material family · Coex
Multi-Layer Coextruded Bags — When a Single Material Cannot Do the Job
Monolayer films have a ceiling: PE seals well but lets oxygen through; PA resists puncture but cannot seal. Coextrusion removes the compromise by engineering each layer for one job — a sealant layer, a barrier layer, a toughness layer — bonded in a single film. If your product needs vacuum packaging, aroma retention or heavy-duty puncture resistance, this is the material family to specify. Tell us the shelf-life target and filling conditions; we engineer the structure to meet them.
Technical profile
Technical Profile — Typical Values
| Common structures | PA/PE, PET/PE, PA/EVOH/PE (3–7 layers) |
|---|---|
| Total thickness | 60–150 µm |
| Oxygen transmission | Low with EVOH/PA barrier layer (OTR typically <10 cm³/m²·24h, structure-dependent) |
| Moisture barrier | High (PE sealant layer) |
| Puncture resistance | High — PA layers absorb impact |
| Heat-seal window | Wide, engineered per sealant layer (PE: 110–150 °C) |
| Service temperature | −30 to +90 °C, structure-dependent |
| Clarity | Good; transparent vacuum-pouch grades available |
| Options | Vacuum, boil-in-bag (to ~90 °C), easy-tear, zipper conversion |
Typical values — customizable to spec. Final parameters are confirmed against your product, filling line and test protocol.
Engineering sequence
How We Specify a Structure — the Engineering Sequence
We do not quote a coex bag from a catalogue thickness. The sequence is:
Product audit
Oxygen sensitivity, moisture target, grease, sharp edges, fill weight.
Process audit
Filling line temperature and speed, vacuum level, distribution stress.
Structure proposal
Layer stack-up with typical OTR/MVTR values, puncture data and seal settings.
Sample validation
Pre-production samples on your actual product; free on standard lines, 3–5 days.
Batch traceability
Structure locked into the production spec for every reorder.
This is the same demand-review → lab → pilot → production workflow our Suzhou R&D centre runs for custom materials, applied to packaging.
Fit check
Where Multi-Layer Coex Performs — and Where It Doesn't
Strong fits
- Food-grade and vacuum packaging — FDA food-contact documentation available; aroma and oxygen barrier for coffee, meat, cheese, sauces. See food packaging.
- Heavy-duty industrial bags — sharp-edged components, powders, high drop-test requirements; see industrial packaging.
- Boil-in-bag and hot-fill to ~90 °C — beyond PE's service ceiling.
Honest limitations
— Multi-material structures are not mechanically recyclable in most streams — if your claim is PCR content or PPWR recycled-content targets, specify rPE or rPP instead, or discuss PCR content in core layers with our engineers.
— Higher tooling and MOQ discipline than monolayer bags — though our MOQ still starts at 500 pcs per design.
— Retort (>100 °C) is outside our standard range; we will say so rather than overpromise.
Evidence
Manufacturing and Compliance Evidence
- Produced in LiHai's integrated plant: 2 pelletizing + 2 film-blowing lines, 8 printing presses (one 10-colour), slitting 800–1300 mm
- Certifications: GRS TE-00057717 · OEKO-TEX SH003 168118 · SMETA ZC5000065444; FDA food-contact and REACH documentation available
- Export documentation prepared for UK, US and EU customs; supplied into UK supermarket programmes and European retail systems (clients under NDA)
- MOQ from 500 pcs; pricing tiers 5,000 / 20,000 / 100,000 pcs; certification package within 24 hours of enquiry
Compare the range
Buyer questions
Frequently Asked Questions
It is structure-dependent, not a single number. A PA/PE structure gives a meaningful improvement over monolayer PE; adding an EVOH core layer brings OTR into single-digit cm³/m²·24h territory (typical values). We propose the structure against your measured shelf-life requirement rather than quoting a generic figure.
Yes, PCR can be incorporated in core layers while keeping food-contact surfaces virgin — this is a real engineering option, but it requires structure design and migration assessment. If recycled content is your primary claim, monolayer rPE/rPP is simpler to certify; discuss the trade-off with our engineers.
Standard-line samples are free and take 3–5 days. For a new coex structure we first agree the layer stack-up in writing, then sample. Enquiries receive an engineer's reply within one working day.
Get started
Request a Structure Proposal
MOQ from 500 pcs per design · free sampling on standard lines (3–5 days) · engineer reply within 1 working day.
Certification package (GRS / OEKO-TEX / SMETA) delivered within 24 hours of enquiry.