Stretch, pre-stretch, cling, puncture: the specs that matter

A stretch film datasheet is mostly a description of the roll. Gauge in microns is how much polymer you are buying per square metre. Width is how much of the pallet face each revolution covers, and it sets how many passes the carriage has to make. Roll length in metres is what you actually consume, which is why film is bought by weight and used by the metre.

Those three set the price. The properties that decide whether the load arrives standing are further down the sheet, if they are on it at all: how far the film stretches, how it clings to itself, how it survives a corner, and how hard the finished wrap is holding. This page takes them one at a time.

Two different things get called stretch. One is the film's capacity — how far the material can be elongated before it thins out and breaks. The other is the setting: how far the film is actually being drawn on your machine on the day. Only the second one shows up on your pallets, and only if the carriage is set and maintained to deliver it.

What you buy with stretch is yield: metres of applied film per kilogram. High yield lowers the cost of every pallet, but only while the containment survives the stretch. Draw a film close to its limit and it has nothing left when it meets a sharp corner — it snaps instead of yielding, and the wrap unzips from the tear. The right stretch level is the one your own machine holds consistently on your own load, not the highest figure the film will reach.

Pre-stretch is elongation applied to the film before it touches the pallet, quoted as a percentage of the original length. On a wrapping machine it happens between two powered rollers on the carriage, the second turning faster than the first. On a factory pre-stretched film it has already been done, and the roll arrives carrying its yield with it.

The distinction matters in practice. Machine power stretch can be tuned to the load, but it depends on a carriage in good order and settings nobody has quietly overridden. Factory pre-stretch behaves the same on a tired machine, in a hand-wrapping bay, or at the end of a long shift — at the cost of being fixed when the roll is made. Hypersonic is Toreto's factory pre-stretched 620 mm film, built for the lowest cost per pallet on standard loads.

Cling is the tack that makes each lap grip the one under it, so the finished wrap behaves as a single sleeve rather than a stack of loose bands. Without it the laps peel apart and the top of the wrap opens in transit, which is where the top cartons start to walk.

The useful version is one-sided. The film grips itself but stays slippery on the outside, so pallets do not weld to each other in the trailer or drag a neighbour's wrap open when they are separated. Which face goes to the goods therefore matters: Toreto's application guide is to put the inside face of the film against the load, because the adhesion is better that way. There should also be enough tack at the finish to swipe the tail down by hand instead of taping it.

Puncture resistance is how well the film resists a point pushing through it — a sharp carton corner, the end of a strap, a forklift tine at the base. Tear resistance is what happens next: whether the hole stays a hole or runs. Most wrap failures are one puncture that was allowed to propagate, and the wrap unzips from it.

This is where structure earns its place. Reinforced film fuses banded reinforcement between its layers, and the bands stop a tear running across the web, which is why Supersonic is the film Toreto puts on heavy and sharp-edged loads. Perforated film is a special case: the holes are deliberate, and the question to ask is whether the strands between them are still carrying the containment force.

Containment force is the inward pressure the wrap applies to the load — what turns a stack of separate cartons into one block. It is read off the wrapped pallet with a gauge, in kilograms per square inch. It is not a property of the roll: it is what the film, the tension, the number of revolutions and the wrap pattern produce together on that particular load.

It is also worth reading twice. Unreinforced film keeps stretching under sustained load and slowly releases its grip, so a pallet that is tight on the dock can be looser the next morning. Tension has an upper limit as well — Toreto's application guide is to tension enough to secure the load fully, but not so much that the wrap crushes what is inside it.

Not per roll, and not per kilo. A roll price compares packaging; a kilo price compares raw material. Neither survives contact with two films that stretch differently. The only honest comparison is per pallet: run both on the same load, on the same machine, at the same settings, then cut the film off each finished pallet and weigh it, count the revolutions and time the cycle.

Then convert. Grams multiplied by your film price per kilogram, plus wrapping minutes multiplied by your labour rate, plus the damage and rewrapping the film is there to prevent. Compare the totals at equal holding force — a cheaper pallet that holds less is not cheaper, it is a different specification.

Toreto's own plant wrap test shows why this is not academic. Two films came out at roughly the same €0.32 a pallet: 12µ nano on 91 g held 7.6 kg/sq in, while Supersonic and Aerosonic at 16µ on 66 g held 10. Solid 23µ film held 9.9 on 200 g, at around €0.48. Same pallet, same machine, same settings — and the cash figures move with film price and pallet size.