Bin liner specification guide: gauge, PCR and seal type
Bin liners look like the simplest thing in packaging and generate more quality complaints than almost anything else, because buyers specify them on micron thickness alone. Thickness is the least informative number on the sheet. Here is what to specify instead.
Two sacks at the same stated gauge can differ by a factor of two in the load they carry, because the resin, the blend and the blowing process matter more than the number.
Why micron alone tells you nothing
A 40 µm LDPE sack and a 40 µm sack blended with LLDPE behave differently: the LLDPE version has far better puncture and tear resistance at the same thickness. A high-PCR sack at the same gauge behaves differently again. And a sack extruded fast on a hot line will have poorer molecular orientation than one run properly, at exactly the same measured thickness.
Worse, gauge itself is often quoted as a nominal figure with no tolerance. Some suppliers quote an average that includes the sealed areas, which flatters the number considerably.
Specify these instead: load rating in kilograms for the intended waste type, gauge with an explicit tolerance, resin blend, and — the one number that cannot be argued with — weight per bag in grams. Weight is what you are actually buying, and it is trivially verifiable on delivery with a set of scales.
The seal is where a bin liner fails, so it is worth specifying deliberately.
Seal type decides where it fails
- Flat bottom seal — a single straight weld. Cheapest, and concentrates all the stress on one line. Fine for light dry waste, poor for anything heavy or wet.
- Gusseted seal — folded sides give a squarer fit to the bin and more volume for the same flat width, but the seal has to pass through multiple film layers, which is a weak point if the welding is not well controlled.
- Star seal — the base is folded so no single point carries the whole load and there are no corners for liquid to collect in. Distributes stress, effectively eliminates leaks, conforms to the bin. This is what to specify for food waste, wet waste or anything above a light load.
Star seal costs marginally more film and materially fewer complaints.
Bin liners are the ideal application for post-consumer recycled content — no food contact, no transparency requirement, and grey is an entirely acceptable colour.
Recycled content: how high is sensible
That means you can go much further here than in any other flexible packaging category. We run 30% to 70% PCR as stable production, GRS-certified. For a UK buyer this comfortably clears the Plastic Packaging Tax threshold with margin against batch variation, rather than sitting nervously at exactly 30%.
What to watch: at high PCR, gel count and colour consistency need managing at the compounding stage, and the load rating must be validated at the actual PCR level you are buying, not inherited from the virgin specification. Ask for the drop test at your specification. More on where PCR performance turns.
If your programme needs compostable rather than recycled, that is a different material and a different certificate — and the certified thickness cap matters. See the compostable standards guide.
Bin liner buyers often ask for a piece-count MOQ and get an answer in tonnes. That is not evasion — it reflects how the cost is actually built.
MOQ, and why it is quoted in tonnes
An extrusion run has a fixed setup cost: purging the line to the new blend, stabilising the bubble, matching colour, and scrapping film until the gauge holds. That cost is the same whether the run is one tonne or ten. Spread across a small piece count on a thin bag, it dominates the unit price; spread across a proper tonnage, it disappears.
Our practical minimum is 3 to 5 tonnes per SKU, which on typical bin liner gauges is roughly 200,000 to 500,000 pieces. A thicker sack means fewer pieces for the same tonnage — that is arithmetic, not a change in commercial terms.
Send the load requirement, waste type, bin dimensions and annual volume, and we will come back with a specification and a tonnage quotation within 24 hours. See the current bin liner range.
Common questions
What thickness should a bin liner be?
Thickness is the wrong specification to lead with. Two sacks at the same micron rating can differ by a factor of two in load capacity depending on resin blend, recycled content and extrusion conditions. Specify load rating in kilograms and weight per bag in grams, with gauge and tolerance as secondary.
What is a star seal and when do I need it?
A star seal folds the base so no single point carries the whole load and there are no corners for liquid to pool in. Specify it for food waste, wet waste or any load above light dry refuse — it costs slightly more film and prevents most leak and burst complaints.
Why is bin liner MOQ quoted in tonnes rather than pieces?
Because extrusion setup cost is fixed per run regardless of quantity. Our minimum is 3 to 5 tonnes per SKU, roughly 200,000 to 500,000 pieces at typical bin liner gauges. A thicker sack gives fewer pieces for the same tonnage.
Where to go next
We answer every enquiry within 12 hours and issue a detailed quotation within 24 hours. Send us a specification.