Technical Specifications for High-Barrier and Specialty Packaging Materials

Specialty packaging materials are specified with technical data rather than by appearance. Two suppliers can offer what looks like the same film or board while performing very differently once moisture, oxygen or grease is involved. This guide explains the specifications buyers most often need to read and compare.

Barrier performance: WVTR and OTR

Water vapour transmission rate (WVTR) measures how much moisture passes through a material in a set time, usually grams per square metre per day. Oxygen transmission rate (OTR) does the same for oxygen. Lower numbers mean a stronger barrier. The test conditions matter, because temperature and relative humidity change the result, so compare figures measured under the same conditions.

The barrier layers behind the numbers

• Metallised PET uses a thin aluminium layer to slow moisture and oxygen
• Aluminium foil offers the strongest barrier but adds weight and cost
• EVOH is a polymer with high oxygen resistance, often used inside a multilayer film
• Coated papers use a dispersion or film coating to resist grease and moisture

Combining layers is common: each one adds a property, and the structure is specified from the outside in.

Thickness, weight and structure

Films are described in microns, papers and boards in grams per square metre, and multilayer structures by the order and thickness of each layer. Ask for the full structure, not only the total thickness, because the position of a barrier layer changes how the pack performs.

Seal and mechanical properties

Heat seal strength, seal initiation temperature and seal through contamination all affect how a pack runs on a filling line. Tear strength, puncture resistance and stiffness decide how the pack feels and survives handling. For flexible packs, the sealing window is often the specification that decides whether a line runs smoothly.

Grease and temperature resistance

Grease-resistant papers are graded with a kit test, where a higher number means resistance to a more aggressive grease. For hot fills or freezer use, confirm the temperature range the material tolerates and how it behaves at the extremes, since some coatings soften or crack outside their range.

Food-contact and compliance

Every layer that touches food must be suitable for the intended use, and documentation should name the substances and the conditions of use. For recycled fibre, a functional barrier may be required. Keep the declarations with the specification so they can be produced during a retailer audit.

How to compare two materials

• Confirm the test method and the conditions used for WVTR and OTR
• Ask for the complete structure and the function of each layer
• Check seal window, strength and machine compatibility for your line
• Request samples to run on your own equipment before committing
• Match compliance documents to the exact material grade quoted

Summary

Technical specifications are the language of specialty packaging. Reading WVTR and OTR with their test conditions, understanding the layer structure, and checking sealing, grease and temperature data turns a vague material offer into a specification you can compare and approve.

Key figures and tolerances

• WVTR: metallised PET 0.3–1.5 g/m²/day, coated (AlOx or PVOH) films 0.3–1.0, foil laminates below 0.1 (ASTM E96 or ISO 15106).
• OTR: metallised PET 1–10 cm³/m²/day, EVOH structures 0.5–5, foil below 0.1 (ASTM D3985).
• Heat seal strength: 15–40 N/15 mm for permanent seals, 5–15 N/15 mm for peelable lids.
• Tear resistance: 100–600 mN trouser tear for typical flexible films (ISO 6383-1).
• Thickness: PET 12–25 µm, PE sealant layers 30–60 µm, foil 7–9 µm.
• Sterile barrier or medical structures are validated to ISO 11607-1.
• Ranges are typical industry values for the material or process named and are not a specification; confirm the exact value, the current edition of each standard and the applicable grade with your supplier or test laboratory.