The short answer
Stretch wrapping pulls the film tight around the load cold. A shrink hood goes on loose, and heat then contracts it. That one difference drives the equipment, the risks and the running costs.
Their numbers do not compare. A lab takes shrink film properties off a small coupon in an oven, while the stretch figure comes off a wrapped pallet, and neither converts into the other.
Choosing between shrink and stretch looks like a materials question. Two plastics, two prices per pallet, and a decision that ought to come down to which number reads better.
The numbers refuse to line up. One method has standardized film properties and no standardized load figure, and the other has a load figure with no standardized method behind it.
So the published comparisons stay qualitative. Energy, speed and film use come down to adjectives, because the measurements that would settle them describe different things.
This reference covers what each process does, what a lab measures on each, why those measurements will not compare, what the heat costs, and what to specify instead.
Two Different Physical Acts
Stretch wrapping works cold. Film leaves the roll under tension, usually pre-stretched before it reaches the load, and that tension squeezes the pallet together.
Shrink works the other way round. A hood of film drops over the load with slack in it, and heat arrives afterwards to pull it in.
That heat needs a tunnel. An equipment supplier’s own comparison describes shrink hooding as requiring a heat tunnel fired by gas burners or electric elements, where stretch hooding needs no tunnel at all.
Everything else follows from that step. The tunnel brings a footprint, services and maintenance points, and it lengthens the cycle in a way the cold process avoids.
The same supplier claims five-sided coverage against dust and moisture for stretch hooding. Treat that as a claim rather than a test result, because the page attaches no measurement to it.
Shrink earns its place on conformity. Heat lets the film follow an irregular load closely, which is why the method survives on lines running awkward shapes.
The supplier splits the applications along exactly that line. Stretch covers a wide range of load types with repeatable results, while shrink reads as the narrower choice for loads that are irregular and need extreme conformity.
What a Lab Measures on Each
Shrink film carries real standardized properties, and they are more specific than most datasheets suggest.
Two published methods carry them, and naming them is worth doing because almost nobody does. ASTM D2838 covers shrink tension and orientation release stress, while ASTM D2732 covers unrestrained linear thermal shrinkage.
One published method covers two separate quantities. Shrink tension names the stress that builds when an oven heats a specimen held at its original length, and the method reports it in pounds per square inch or megapascals.
The arithmetic behind it is plain. The lab divides the maximum force it recorded by the cross-sectional area of the strip, which is why the result arrives as a pressure rather than a force.
The second quantity is what survives the shrinking. For orientation release stress the lab lets a specimen shrink freely, re-clamps it at its new shorter length, reheats it, and records the force left in it.
That residual figure speaks to the long run. It describes the dimensional stability of the formed package rather than the grip it had on the day somebody wrapped it.
Specimen detail matters as much as either number. The lab cuts pieces in both the machine and transverse directions, 25 millimeters wide, and holds the oven or oil bath to within one degree Celsius.
The method also keeps the two film directions apart rather than averaging them, so a datasheet carrying a single figure has dropped half of the result. A hood sits on the load in one orientation, which makes the stronger axis part of the specification rather than a detail.
The method fixes no test temperature either, which is the familiar catch. The test runs at whatever temperature a specification names, so a shrink tension figure means little without that temperature beside it.
The companion method answers a different question, measuring unrestrained linear thermal shrinkage. That is how far the film moves, where shrink tension is how hard it pulls, and a datasheet quoting one tells you nothing about the other.
The stretch figure sits somewhere else entirely. A wrapped load’s performance number is its containment force, and as covered elsewhere on this site, no method standard produces it.
The specimen is the difference: a whole load on one side, a strip of film on the other.
Why the Two Numbers Will Not Compare
Set the two measurements side by side and the mismatch turns out to be structural rather than a matter of precision.
| Stretch | Shrink | |
|---|---|---|
| Heat | None | Tunnel required |
| Measured on | The wrapped load | A film coupon |
| Quantity | Containment force | Shrink tension, ORS |
| Units | Force | psi or MPa |
| Method standard | None for the figure | Published |
| Best at | Repeatable regular loads | Conformity on odd shapes |
The specimen differs first. One figure comes off a pallet somebody wrapped, and the other off a strip of film in an oven that never touched a product.
Units differ next, because pressure and force are not the same quantity. Dividing a load figure by an area somebody guessed at will not turn one into the other.
Direction differs as well. A lab takes film properties along the machine and transverse axes separately, while a load figure gets read at heights up the pallet.
Which leaves the comparison where the literature leaves it. Equipment suppliers claim lower energy, faster cycles and less film without attaching a figure to any of the three.
The throughput claims run the same way. Stretch hooding gets described as faster and suited to high-volume automation, and shrink as slower for the added heat step, with no cycle times or pallets per hour anywhere.
Which is worth knowing before a capital decision rests on it. An adjective from a vendor is a starting point for a question, not an input to a payback calculation.
What the Heat Costs
Heat buys conformity, and it charges in several places worth knowing before a line gets built around it.
The first charge lands on your own packaging. Shrink film can bind to primary plastic packaging as it contracts, so a polybagged or sleeved product can emerge fused to its own unit load.
The second lands on the film. Shrink film can thin during shrinking wherever the load moves, which puts the weakest section exactly where the geometry happened to shift.
Thickness compensates and costs. Shrink lines often run heavier film to survive the heat, which the supplier pairs with a higher waste risk.
The third charge lands on the product. Higher shrink tension gives a tighter package, and the method’s own guidance warns that excessive tension can crush, distort or deform fragile packaged goods.
That last one is a fragility question rather than a film question. A product fragility ceiling applies to the slow squeeze of a contracting hood just as it does to an impact.
The line itself pays too. The supplier lists more maintenance points, higher downtime risk, additional safety considerations and less flexibility at changeover for the heated process.
Against all of that sits the real advantage. A heated hood follows an irregular load that cold film would simply bridge across, and no amount of tension reproduces that.
What to Put on the Specification
Since the datasheets will not settle it, the specification has to describe the outcome at the load.
For stretch, write a containment force target together with the tool that measures it, the position on the load, and the procedure. The figure is not enforceable without all three.
For shrink, name the film property at the temperature your tunnel actually runs. A shrink tension figure quoted without its test temperature describes a test nobody specified.
So ask the line for its real number, not its rating. Tunnel temperature drifts with line speed and ambient conditions, and the figure that matters is the one the film actually sees.
Then test the load rather than the film. A load-stability check answers whether the unitized pallet holds, which is the question both methods exist to settle.
Two further constraints belong on the same drawing. The footprint comes from standard pallet sizes, and whatever the wrap achieves, the stack still has to respect the safe stacking load of the boxes underneath.
All of which makes this a process decision rather than a numbers comparison. Choose on heat tolerance, load shape and the equipment you can service, then specify performance where somebody can measure it.
Common Questions
Is shrink wrap stronger than stretch wrap?
Published figures cannot answer that. A lab takes shrink film’s standardized properties off a small coupon in an oven, while the stretch figure comes off a wrapped load, and neither converts into the other. A load-stability test on the actual unitized pallet is what compares them.
Why does shrink wrapping need heat and stretch wrapping does not?
Because the tension arrives differently. Stretch film goes on already drawn tight, so the tension is mechanical and cold. A shrink hood goes on with slack and contracts only once heated, which is why the process needs a tunnel fired by gas burners or electric elements.
What is shrink tension, and how does it differ from shrinkage?
Shrink tension is how hard the film pulls: the stress that builds when an oven heats a specimen held at its original length, in psi or MPa. Shrinkage is how far the film moves, which a separate method covers as unrestrained linear thermal shrinkage. One is pressure, the other is distance.
Can shrink wrapping damage the product?
It can, in two ways. The film can bind to primary plastic packaging as it contracts, fusing a product to its own unit load. Separately, the method’s guidance warns that excessive shrink tension can crush, distort or deform fragile goods, so the squeeze itself carries a ceiling.
How to weigh this page. The shrink film method detail comes from a test laboratory’s published explanation of the standard rather than from the standard itself. The process differences come from an equipment supplier’s own comparison, which is one-sided by nature. Its energy, cycle time and film savings claims carry no figures, and it lists no drawbacks for the method it sells. Nothing here quantifies energy, throughput or film use, because no source read does. Where the choice is already settled, specify the performance at the load and ask for a test report rather than a datasheet.
Key takeaways
- Stretch film goes on cold and already drawn tight, while a shrink hood goes on loose and contracts under heat from a tunnel.
- Shrink film carries standardized properties: shrink tension in psi or MPa, and orientation release stress, on 25 mm specimens cut in both film directions.
- That method fixes no test temperature, so a shrink tension figure means little without the temperature beside it.
- The stretch figure is containment force on a wrapped load, with no method standard behind it, so the two sets of numbers will not compare.
- Heat buys close conformity on irregular loads and risks binding to primary packaging, thinning the film where the load moves, and deforming fragile contents.