Layflat tubing explained: one reel, any bag length

What is layflat tubing?

Layflat tubing is polythene made as a continuous tube and wound flat onto a reel. It has no side seams and no end seals, so what comes off the reel is an open sleeve. Cut a length off and seal one end and you have a bag; seal both ends and the item inside is fully enclosed.

The tube is round when it leaves the extruder and is collapsed flat before winding, which is why tubing measuring 300mm across the reel opens out to a sleeve of roughly 600mm around.

It is bought by the reel and specified by flat width and gauge rather than by width and length, which is the switch most buyers make when they move off pre-made bags.

How is layflat tubing made on a blown film line?

Layflat tubing is made by blown film extrusion. Polythene granules, plus any colour masterbatch or additive, are fed into an extruder where a rotating screw melts and mixes them and pushes the melt through a circular die, which forms it into a thin tube.

Air is blown up through the centre of the die and trapped inside that tube, inflating it into a tall bubble. The trapped air sets the diameter, and therefore the flat width, so an operator changes width by adding or bleeding air. The ratio of bubble diameter to die diameter is the blow-up ratio: inflating further stretches the film more around its circumference and evens up tear and impact strength in both directions.

An air ring cools the bubble, and the height at which the melt turns solid, called the frost line, is another setting that influences film properties. Above it, a collapsing frame folds the bubble flat and nip rollers pull it up the tower and pinch it closed. How fast those rollers pull, against what the extruder is pushing out, sets the thickness: pull faster and the film draws down thinner.

The flattened tube is wound onto a reel, usually with part of the line rotating so small gauge variations spread across the roll instead of stacking into a ridge. That reel is the natural output of the process: sheeting is tubing with one or both folded edges slit off, and a pre-made bag is tubing cut and sealed on a converting machine. We do both in house in Blackburn.

Why can you make any bag length from layflat tubing without new tooling?

On a reel of layflat tubing the width of the bag is fixed but the length is not. Width is decided on the extrusion line by the die and by how far the bubble is inflated, before the film is wound. Length is decided by wherever you cut and seal, which costs nothing and takes a second at the bench.

That is why buyers with variable-length products use tubing. A fabricator handling bar, tube and profile in a dozen lengths would otherwise need a dozen bag sizes, each with its own set-up, minimum order quantity and space on the racking. One reel of the right flat width covers all of them, including the one-off that no standard bag fits.

The trade-off is labour, because every bag made from tubing needs a cut and at least one seal at your end. Tubing wins when sizes vary, when volumes per size are low, or when short items are currently going into a bag bought for the long ones.

How do gussets work on layflat tubing?

A gusset is a fold tucked into each side of the tube before it is wound, formed by gusseting plates that press into the bubble as it is collapsed. Plain tubing lies flat as two layers; gusseted tubing has the sides folded inwards, so it opens out into a square-sided sleeve rather than a flat pouch.

The arithmetic is worth knowing before you order. Film all the way round a gusseted tube is twice the flat width plus four times the gusset depth, and the tube opens out to a sleeve the flat width across by twice the gusset depth deep. Tubing at 400mm flat with 100mm gussets therefore uses the same film per metre as plain 600mm tubing, and opens out to roughly 400mm by 200mm. Work back from the load you are covering, not from the bag you are replacing.

Gussets earn their place for three reasons. They let the film sit against a square load rather than bridging the corners, which is where unsupported film tears. They keep the reel narrower for a given circumference. And they change sealing, because a bar crossing a gusset fuses four layers at the fold and two elsewhere.

How do you cut and heat seal layflat tubing?

Layflat tubing is cut with a blade against a bench, a guillotine, or a hot wire that cuts and seals in one pass. Most benches pull the length they want off a reel dispenser and cut against a bar.

Sealing is where technique matters. An impulse sealer passes current through a thin element for a set time, melts the two layers together, then holds them under pressure while they cool. A constant heat sealer keeps a bar at temperature and suits heavier gauges, which need more energy than an impulse element comfortably delivers. A rotary band sealer seals continuously as the bag passes through, which suits volume work.

Three habits prevent most seal failures. Let the seal cool under pressure before the bag is moved, because polythene has very little strength while hot and a seal pulled apart early will peel. Increase the dwell time as the gauge goes up, and again where the seal crosses a gusset and has extra layers to fuse. Keep the jaws clean, since dust, oil or product trapped in the seal is the usual reason one looks right and then opens in transit.

If you would rather not seal in house, we convert the same tubing into finished bags and covers at our Blackburn factory.

What is layflat tubing used for?

Layflat tubing is used wherever the product is long, awkward or changes size from order to order. Engineering and metal fabrication is the classic case: bar, tube, extruded profile and machined parts come in lengths that vary, and a sleeve cut to fit keeps swarf, moisture and handling damage off the surface. Timber, joinery and roll goods such as carpet, textiles and paper are handled the same way.

It is also the base material for a lot of finished covers. A pallet cover is gusseted tubing cut to the load height and sealed across the top. Mattress and furniture covers are wide gusseted tubing sealed at one end. Box and case liners are plain tubing cut short and folded over rather than sealed at all.

Beyond protection, tubing is used for kitting and containment: sleeving a set of parts together, lining a stillage or tote, or covering machinery in storage. Anti-static grades suit static-sensitive contents, and printed tubing carries part numbers or handling instructions with the item. If you are unsure which format suits your product, our product selector narrows it down.

How do you specify and order layflat tubing?

Specifying layflat tubing takes four numbers and two choices: flat width, gusset depth if you need one, gauge in microns, reel length or weight, then colour and whether it is printed. Width and gusset come from the item's dimensions, with enough room for it to slide in rather than be forced. Gauge comes from its weight, whether it has sharp edges, and how much handling it takes on the way to its destination.

As a starting point, 25 to 50 micron suits light, clean items and dust covers, mid gauges cover general packing, and heavy, sharp or abrasive goods want 100 micron and upwards. We extrude from 25 to 250 micron and make the flat width to order. If a thickness has been quoted to you in gauge or mil, our polythene thickness converter will translate it.

Lead times are typically 2 to 3 weeks on bespoke runs and quicker on repeats and standard specifications. Minimum order quantity varies by product and gauge, and we support one-off bespoke trials, so proving a specification on a first run is a reasonable request. Send the dimensions, the weight and a note on handling, and we will recommend a specification.

Frequently asked questions

What is the difference between layflat tubing and polythene sheeting?

Layflat tubing is a closed tube, and polythene sheeting is that same tube with one or both folded edges slit off so it lies as a flat web. Because tubing has no seams down its sides, a bag made from it only needs the ends sealing. Sheeting is the better buy when you are covering, lining or wrapping and do not need a sleeve at all.

How do I work out the flat width of layflat tubing I need?

Measure the item across its widest cross-section and choose a flat width that lets it slide in without being forced. Plain tubing at a given flat width opens to a sleeve roughly twice that measurement around, so 300mm flat gives about 600mm of circumference. For a square or boxed load, use gusseted tubing and work back from the load: film all round is twice the flat width plus four times the gusset depth.

Do I need machinery to use layflat tubing?

No. A blade and a hand impulse sealer are enough for most gauges, and heavier film is better served by a constant heat bar or a foot-operated sealer. Volume users add a rotary band sealer so bags can be sealed continuously rather than one at a time. If you would rather not seal anything in house, we convert tubing into finished cut and sealed bags and covers at our Blackburn factory.

Can layflat tubing be printed?

Yes, we print layflat tubing to your artwork. It is normally used for part numbers, handling instructions, batch identification or branding where the customer sees the wrap. Print is set up per specification, so send the artwork with the flat width and gauge and we will quote it plain and printed for comparison.

Is layflat tubing available in recycled polythene?

Yes. Recycled grades are available across much of our range, and tubing is one of the easier products to build recycled content into because it is usually a protective sleeve rather than a presentation pack. Biodegradable options are manufactured too. Tell us how the tubing is used and how much handling it takes, and we will suggest how much recycled material the specification will carry without losing protection.