A practical guide to matching grease, liquid-water, vapour, oxygen and heat-seal needs with paperboard coatings, liners and documented food-contact performance.
Define the exposure before naming a barrier
Grease resistance, water resistance and water-vapour resistance are different jobs. Aroma retention, oxygen control and heat sealing introduce further requirements. Fill temperature and the time between packing and consumption belong in the same brief.
| Barrier need | What it protects | What to verify |
|---|---|---|
| Grease and oil | Visible staining, edge wicking and loss of board strength | Food fat, temperature, score lines, cut edges and hold time |
| Liquid water | Leakage and rapid softening from sauces or condensation | Free-liquid volume, seams, closure and dwell time |
| Water vapour | Moisture gain or loss during longer storage | Storage period, humidity and an appropriate WVTR target where relevant |
| Oxygen and aroma | Oxidation, flavour loss and odour transfer | Product sensitivity, storage life and an appropriate OTR or aroma test where relevant |
| Heat seal | Closure integrity on lined or coated webs | Seal temperature, pressure, dwell time and contamination at the seal |
Distinguish direct contact from secondary packaging
A structure touching food needs a different review from an outer box holding a sealed inner pack. Identify every contact surface, liner, coating, adhesive and printed area. In Canada, the food seller remains responsible for ensuring that packaging does not transfer harmful substances to food, so supporting documents must match the intended conditions of use.
Compare coating and liner routes without shortcut claims
The best route balances protection, forming, sealing, appearance and end-of-life conditions. No coating family is automatically suitable for every food or automatically recyclable in every local collection system.
| Material route | Potential strengths | Trade-offs to review |
|---|---|---|
| Aqueous dispersion coating | Thin barrier layer, print compatibility and potential fibre recovery when designed appropriately | Exact chemistry, coat weight, heat resistance, repulpability and local acceptance |
| Polymer extrusion or lamination | Robust liquid, seal or long-hold performance for demanding uses | Fibre separation, polymer content, forming at scores and local recycling route |
| Bio-based coating | Renewable-content possibilities and targeted grease or moisture performance | Food-contact evidence, heat performance, industrial processing needs and verified end-of-life claim |
| Separate liner or inner pack | Lets the paper outer pack focus on structure and communication | Component separation, material use, packing workflow and customer disposal instructions |
Treat repulpability and PFAS-free claims as separate questions
A PFAS-free grease barrier addresses a chemical-selection concern; it does not by itself prove recyclability. Repulpability depends on how the complete construction behaves in a paper recycling process, while practical recyclability also depends on sorting and local market acceptance.
- Request evidence for the exact coating and board combination
- Check how adhesives, inks, windows and liners affect the complete pack
- Use market-specific disposal language instead of a universal claim
Test representative exposure and record the approval basis
Use representative contents to check staining, softening, leakage, odour transfer, closure and handling over the expected holding period. Cobb, KIT, WVTR, OTR, seal or migration data are useful only when they answer a real requirement. Final suitability should be supported by the supplier documentation required for the product and destination market.
