The three-layer structure explained
Most flexible packaging is built from three functional layers. The outer layer carries the print and protects against abrasion and moisture during handling. The middle layer provides the barrier, often using aluminium foil, metallised film or a high-barrier polymer. The inner layer is the sealant, chosen for heat-sealing and direct product contact. Each layer is laminated with adhesive, so the structure is described by its film sequence, such as PET/AL/PE or PET/NY/PE.
Reading a structure from outside to inside tells you what the pack can and cannot do. A two-layer PET/PE pouch handles dry snacks but not coffee. A three-layer PET/AL/PE structure blocks oxygen, moisture and light, which extends shelf life for oxygen-sensitive products. Buyers who understand this sequence can compare quotations on a like-for-like basis instead of comparing only the total micron count.
Common film materials and their roles
BOPP is a clear, glossy film with good moisture resistance and printability, widely used for snack and confectionery wrappers. PET offers strength, temperature resistance and print quality, often as the outer layer. PA, or nylon, adds puncture and flex-crack resistance, useful for vacuum packs and frozen food. CPP is a sealant for retort and high-temperature applications, while PE is the workhorse sealant for pouches, offering good moisture barrier and low cost.
Aluminium foil provides the highest barrier against light, oxygen and moisture, but it is opaque and can crease. Metallised films give a reflective appearance and moderate barrier at lower cost. Kraft paper laminates suit brands that want a natural look with a grease-resistant inner layer. Mono-material PE and PP recyclable structures, plus PLA/PBS compostable options and degradable films, are available where end-of-life requirements drive the brief.
Matching barrier to the product
Barrier requirements follow the product's sensitivity. Coffee needs an oxygen and moisture barrier plus a one-way degassing valve to release carbon dioxide without letting oxygen in. Snacks need moisture and grease resistance. Pet food needs oxygen and light protection to preserve fats. Tea needs aroma retention and moisture control. For each case, the film structure and any add-on such as a valve, zipper or window are chosen together.
Over-specifying barrier raises cost and can slow lead times. Under-specifying it shortens shelf life and causes complaints. A useful starting point is to define the required shelf life, storage conditions and acceptable moisture or oxygen ingress, then let the converter recommend a structure. Testing a stock pouch sample with your actual product is a practical way to validate the choice before committing to a print run.
Filling methods and pouch formats
The filling method affects the pouch format. Flat bottom pouches stand upright on the shelf and fill well on automatic lines. Stand up pouches are versatile for snacks, coffee and pet food. Flat and three-side-seal pouches suit small sachets and single servings. Spout pouches, including corner spout and STANDCAP, work for liquids, sauces and purees. Side gusset bags handle larger fills such as coffee beans and tea leaves.
Rollstock film is the choice for form-fill-seal lines, where the pack is made, filled and sealed in one pass. Special shaped bags allow a distinctive silhouette but may need manual or semi-automatic filling. The decision should account for fill weight, product density, line speed and the seal integrity required. A pouch that fills well on a manual line may not run on a high-speed VFFS machine without adjustments.
What drives the price of a pouch
The main cost drivers are film structure, print method, order quantity and add-ons. Rotogravure printing uses engraved cylinders, so it offers up to 10 colours and low unit cost at high volumes, with tooling costs and longer setup. Digital printing has no cylinder cost and suits short runs, making it economical from 100 pcs for pouches or 10 kg for film. Rotogravure becomes more competitive from 10,000 pcs or 200 kg.
Add-ons such as a degassing valve, zipper, tear notch, window, spout and cap, carry handle or hang hole each add material and process steps. Lead time also differs: digital print runs typically take 10-15 working days after artwork approval, while rotogravure runs take 20-25 working days. Buyers comparing quotes should check the structure, print method, MOQ and lead time, not just the unit price.
Sustainability rules and common mistakes
Recyclability rules increasingly favour mono-material structures such as PE/PE or PP/PP, because multi-material laminates are harder to separate. Compostable options like PLA/PBS suit specific disposal streams, but they need the right collection and processing conditions to break down. Degradable films are a separate category and should not be confused with recyclable or compostable. The right choice depends on the market's labelling rules and the waste infrastructure your customers actually have.
Common mistakes include choosing a structure before defining shelf life, ignoring the filling line's seal parameters, and ordering artwork-ready files too late. Another is assuming a stock pouch sample behaves the same as a printed production run. Free stock pouch samples are available, with the customer paying courier only, which lets buyers test fit, fill and barrier before committing. Certifications belong to the manufacturing partner, so ask for the relevant documents for your market.