Choosing between evoh vs pvdc barrier plastic layers is one of the recurring decisions in flexible and thermoformed food packaging. Both resins sit in the middle of a coextruded structure as a thin oxygen barrier, and both can deliver transmission rates below 1 cm³/m²·day under laboratory conditions. Yet they behave differently the moment humidity, heat or recycling enters the picture, and those differences decide shelf life, line speed and end-of-life compliance. This guide compares the two barrier layers on the numbers buyers can actually specify.
What evoh vs pvdc barrier plastic selection really compares
Neither resin is used alone. Both appear as a 3-8 μm layer sandwiched between polyolefin or PET structural layers, bonded with tie layers, so the comparison is never resin against resin in isolation. It is a comparison of how each barrier layer performs inside a finished structure across the whole distribution cycle: dry storage, refrigerated transport, retail humidity swings and the consumer's kitchen. Datasheet values quoted at 0% relative humidity describe a warehouse that does not exist.
Barrier performance: oxygen, moisture and humidity
The defining difference is how each material responds to moisture. The EVOH oxygen barrier is excellent in dry conditions: hydroxyl groups hydrogen-bond tightly until water molecules plasticise the chain, at which point oxygen transmission climbs steeply above roughly 60% relative humidity. The PVDC moisture barrier is far less sensitive to humidity, holding a stable oxygen barrier from dry to saturated conditions, and PVDC also blocks water vapour an order of magnitude better than EVOH.
| Property (typical, 20 μm layer) | EVOH (32% ethylene) | PVDC (extrusion grade) |
|---|---|---|
| Oxygen transmission, dry, 23 °C | 0.2-1.6 cm³/m²·day | 1.2-9.2 cm³/m²·day |
| Oxygen transmission at 80% RH | Rises several-fold | Largely unchanged |
| Water vapour transmission | 24-120 g/m²·day | 0.8-3.2 g/m²·day |
| Processing window | 180-220 °C, needs tie layers | Narrow; decomposes near 190 °C |
Processing and barrier layer coextrusion behaviour
Barrier layer coextrusion with EVOH runs on standard polyolefin lines: the resin processes at 180-220 °C and adheres through maleic-anhydride tie layers to PE or PP. PVDC is more demanding. Its thermal stability window is narrow, decomposition begins near 190 °C with hydrogen chloride evolution, and dies often need nitrogen purging to protect the melt. PVDC lines also run slower and need tighter temperature control, which shows up as scrap rate and downtime rather than as a line item on the resin invoice.
Recycling, regulation and end of life
EVOH is chlorine-free and, at limited loadings with a compatibiliser, can be tolerated in PE recycling streams under current design-for-recycling guidance. PVDC carries chlorine, and multilayer structures containing it are incompatible with standard polyolefin recycling, which pushes them toward incineration or specialist processing. On the compliance side, both resins are used in food contact structures under EU and US rules, but PVDC structures carry migration limits for vinylidene chloride residues, so suppliers should provide declarations rather than a generic food-safe statement.
Grades, ethylene content and retort duty
EVOH grades are split by ethylene content: 27-32 mol% ethylene maximises oxygen barrier for dry structures, while 38-48 mol% grades trade some barrier for thermoformability, flexibility and lower humidity sensitivity. The grade choice must match the converting route, because a deep-draw thermoformed tray and a flat cast film do not want the same resin. Retort and hot-fill structures add a further constraint: EVOH needs protective outer layers and tight process control, since prolonged heat and moisture during sterilisation accelerate the plasticising effect that erodes its barrier.
Writing the choice into an RFQ
Specify the structure, not the brand: state the target oxygen and water vapour transmission at the humidity the product will actually see, the layer thickness, the tie layers and the retort or hot-fill duty if any. Ask for measured OTR on the finished film rather than the resin datasheet, and request the food contact declaration and recyclability assessment in the same package. Where a structure will see high humidity, ask for aged OTR data after a humidity exposure cycle rather than a single dry reading, because that is the number that predicts shelf life on the shelf. For more context, see the plastic materials hub, the vacuum bag barrier guide and the PP vs PET packaging comparison, or compare suppliers via the verified manufacturer directory.
