Shrink Band Shrink Ratio Explained: TD vs MD, Shrink Percentage & Fit

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Quick answer. A shrink percentage is not a bottle-size formula. It describes how much a heat-shrinkable film can contract in a stated direction under stated test conditions. A supplier that writes “60% shrink” without identifying direction, temperature, exposure time, and film grade has not given you enough information to compare the material reliably.

For shrink sleeves and many neck-band films, the large contraction is commonly engineered in the transverse direction (TD), while machine-direction (MD) shrink is kept much lower. In a typical converted sleeve, TD becomes the circumferential direction and MD becomes the height direction — but confirm that orientation with the converter rather than assuming it from the words alone.

Use shrink ratio to screen whether a film has enough recovery for your package geometry. Use lay-flat width and cut height to choose the starting band dimensions. Then validate the finished band on the real bottle, cap, perforation, and heat process. Those are three different decisions.

What Does “Shrink Ratio” Mean on a Shrink Band?

In shrink-film purchasing, shrink ratio is usually expressed as a percentage change in a linear dimension after heating. If a 100 mm film strip becomes 60 mm long under the stated test, the unrestrained linear shrink in that direction is 40%. The percentage describes recovery from the oriented state; it does not mean the band should be ordered 40% larger than the cap.

ASTM D2732 treats unrestrained linear thermal shrinkage as a temperature-dependent property of plastic film. The standard is useful here because it makes the central procurement point explicit: shrinkage has to be tied to specimen temperature, and a material can be characterized across several temperatures through its shrink range. A single percentage with no test condition is therefore an incomplete specification.

Also avoid confusing film shrink percentage with heat-shrink tubing ratios such as 2:1 or 3:1. Electrical tubing uses a different sizing convention based on expanded and recovered diameters. Bottle and jar shrink bands are normally bought by lay-flat width, height/cut length, material, and other film/converting specifications, with percentage shrink used as a film-performance field.

TD vs MD: Which Direction Is Actually Shrinking?

Machine direction (MD) runs along the direction the film travels through manufacturing and converting equipment. Transverse direction (TD) runs across that web. Oriented films can be engineered to recover very differently in those two axes because the manufacturing process stores different amounts of molecular orientation in each direction.

That directional behavior is central to sleeve packaging. Technical literature on oriented films describes transverse-oriented materials used where strong shrink is wanted around the container while much less shrink is wanted in the other axis. Current sleeve-film data sheets commonly show the same pattern: a large TD value and a small MD value. The exact numbers vary by resin grade, orientation process, and test condition.

For a conventional seamed sleeve, the high-shrink direction is typically arranged around the circumference while the low-shrink direction runs vertically. That helps the film pull into shoulders, rims, and neck transitions without shortening the sleeve excessively. For a pre-cut neck band, however, ask the supplier which converted dimension corresponds to TD and MD. The words “width” and “height” on a marketplace listing do not prove film orientation.

Why One Film Does Not Have One Universal Shrink Percentage

Shrink is activated by heat, and the amount of recovery depends on how the film was made and how it is heated. ASTM D2732 notes that the magnitude of shrinkage varies with film temperature. Experimental work on heat-shrinkable PVC similarly found that percentage shrink increased with temperature and depended strongly on draw ratio. Research on blown shrink films also shows that processing conditions and directional orientation change the final shrink response.

That is why a serious technical data sheet often gives something closer to “TD 70% at 90 °C for 10 seconds” than simply “70%”. Some suppliers publish shrink curves rather than one endpoint. A curve is more useful for process development because it shows how recovery develops across temperature instead of implying that the film instantly reaches its maximum value.

Your heat gun or tunnel does not automatically reproduce a laboratory water-bath or oven test. Air temperature, steam, exposure time, line speed, distance, package thermal mass, and how evenly heat reaches the circumference all change the actual package response. Treat the published percentage as a standardized material reference, not as a promise that every finished bottle will contract by exactly that amount. The heat gun versus hair dryer versus heat tunnel comparison covers how the heat method changes what the film actually does.

How Much Shrink Does Your Package Geometry Require?

You can use package geometry for a screening calculation, as long as you keep it separate from the final size decision. If the unshrunk tube circumference at the relevant section is C0 and the smallest circumference the film must reach is C1, the theoretical local circumferential reduction is:

Required local reduction (%) = (C0 - C1) / C0 × 100

Example: a tube circumference of 100 mm that must recover onto a 72 mm neck requires about 28% local circumferential reduction. That does not mean “buy 28% shrink film.” It means the material/process combination must have enough usable recovery to reach that geometry without creating unacceptable stress, distortion, split perforations, or poor seating.

The same package may require different local recovery at different heights. A straight cap wall may need very little contraction, while the film immediately below a wide cap flange may have to draw down much farther onto the neck. That is why the hardest contour, not the average bottle diameter, controls the shrink-capability question.

Keep Size, Shrink Ratio, Thickness & Shrink Force Separate

Field	What it controls	Do not use it as
Lay-flat width	Starting tube fit around the widest required feature	A shrink-percentage measurement
Band height / cut length	Vertical coverage across cap and fixed neck	A measure of circumferential shrink capability
TD / MD shrink %	Directional thermal recovery under stated test conditions	A direct replacement for lay-flat sizing
Film thickness	Physical gauge of the film	A proxy for shrink percentage or quality
Shrink tension / force	Force generated while oriented film recovers	The same thing as free shrink percentage
Material / grade	Resin system plus formulation/orientation choices	A guarantee that every grade has one fixed shrink value

This separation matters because supplier pages often place several of these fields beside each other. A 50 µm film with 70% TD shrink is not “70% stronger,” and a 2 mil band is not automatically a lower- or higher-shrink material. The thickness guide covers thickness normalization and the shrink band size guide covers lay-flat and fit.

Is Higher Shrink Always Better?

No. Higher available shrink can be useful when the package has a large circumference change, deep shoulder, cap flange, or other contour that requires substantial recovery. But “higher” is not a standalone quality score. The film still has to run through the available heat process, maintain acceptable band height, preserve the perforation, and finish without wrinkles, splits, or excessive distortion.

For a simple cylindrical cap and neck, a very high-shrink grade may provide capability that the package never needs. For a difficult contour, a lower-shrink grade may simply run out of recovery before it reaches the fixed neck. The correct question is not “Which film has the largest percentage?” It is “Does this exact film grade have an appropriate shrink curve and directional balance for this exact geometry and process?”

This is also why PETG-versus-PVC cannot be decided from one generic shrink number. Individual grades within a material family can be designed for different shrink levels. Material choice, shrink curve, MD/TD balance, thickness, perforation, and process window should be treated as separate but interacting fields.

What Should You Ask a Supplier for?

If shrink behavior is important to the buying decision, move beyond a marketplace title and ask for the actual grade data. The minimum useful request is the film material/grade plus TD and MD shrink values with their test condition. For a custom band, also send the real closure geometry or physical sample and ask the supplier to confirm which film direction wraps the circumference.

RFQ field	What to request	Why it matters
Material / grade	Exact PVC, PETG, PET, OPS, or supplier grade used for this order	Different grades can have different shrink curves
TD free shrink	Percentage plus temperature and exposure time/test method	Screens circumferential recovery capability
MD free shrink	Percentage plus the same test condition	Shows how much height may change
Shrink curve	If available, shrink % across several temperatures	Better than one endpoint for process planning
Converted orientation	Confirm which finished-band dimension corresponds to TD and MD	Prevents width/height orientation assumptions
Lay-flat + height	Nominal dimensions and tolerances	Controls physical fit and coverage
Perforation	Pattern, position, and opening direction	Shrink can affect tear-line behavior
Sample validation	Pre-production sample on the actual package	Confirms the full package/process, not just the film data

A concise RFQ sentence can be: “Please quote the finished neck band for the attached bottle/closure, and confirm film grade, lay-flat, cut height, dimensional tolerance, perforation, TD and MD free-shrink values with test temperature/time, and sample availability before production.”

How to Validate the Band on the Actual Bottle

Do not try to prove the supplier’s laboratory percentage by measuring one shrunk band on a bottle. Once the film contacts the cap and neck, the package constrains the recovery. Your validation target is the finished-package function.

Start with the correct assembled bottle and closure. Record the unshrunk band lay-flat and height, then apply it with the intended heat source. After cooling, check whether the band fully bridges the removable closure and fixed container, whether the bottom edge has seated where intended, and whether the band has shortened enough to expose a seam or label area. Inspect the perforation before and after opening.

Repeat across several units and, for production, across start-up and steady running. If a defect repeats at the same cap feature, the issue may be geometry, band size, perforation position, or insufficient usable shrink. If defects move around the circumference, heat distribution or operator/process consistency becomes more suspect. The wrinkles, splits and uneven-shrink troubleshooting guide covers that diagnostic path in detail.

Current Alibaba Sourcing Options

The three options below are organized by buyer role in this guide: a conventional PVC finished-band baseline for the practical fit trial, a custom PVC/PETG comparison route for requesting exact film data, and a custom/scale-up specification route after behaviors are locked. Marketplace terms change — recheck the live listing, material, dimensions, MOQ, sample terms, and CPS destination before ordering.

How to use these options: start with the PVC finished-band baseline to validate the actual package, use the custom PVC/PETG route to request exact material and TD/MD test data, and move to the custom scale-up path only after lay-flat, height, material, perforation and shrink behavior are locked on samples. Confirm the film grade and MOQ on the live listing before ordering.

Frequently Asked Questions

Is 60% shrink enough for a bottle-neck band?

Maybe, but the number is incomplete by itself. You need to know the direction and test condition, then compare the available recovery with the hardest local circumference change on the actual package. The final answer still requires a sample trial.

Is 75% PETG automatically better than 55% PVC?

No. A higher published maximum can be useful for more demanding geometry, but material choice also affects processing, shrink curve, force, printing/converting, recycling requirements, and the exact supplier grade. Compare the complete specification, not one percentage.

Can I calculate shrink-band size from the shrink percentage?

No. Size starts with the actual package geometry, supplier fit range, lay-flat width, and band height. Shrink percentage is a material-performance field used to judge whether the film can recover sufficiently after it has been placed over the closure.

Does thicker film shrink less?

Not as a general rule. Thickness and thermal shrinkage are separate properties. Two films with similar thickness can have very different orientation and shrink curves, while films with different thicknesses can be engineered to similar shrink targets.

What Does a Low MD Shrink Value (under 3%) Mean?

It means the supplier reports less than 3% linear shrink in the machine direction under the stated test condition. For a conventional sleeve orientation, low MD shrink is often used to limit unwanted vertical shortening, but confirm how the finished band was converted.

Will a heat gun reproduce the supplier’s laboratory shrink value?

Not necessarily. A laboratory test controls temperature and exposure in a defined way. Manual hot air creates a different heat-transfer pattern, and the bottle itself constrains the film. Use the data sheet to understand the material and use package trials to approve the process.

References

1. Pietrosanto, A., Apicella, A., Scarfato, P., Incarnato, L., & Di Maio, L. (2022). Development of Novel Blown Shrink Films from Poly(Lactide)/Poly(Butylene-Adipate-co-Terephthalate) Blends for Sustainable Food Packaging Applications. Polymers, 14(14), 2759. DOI: 10.3390/polym14142759
2. Hong, C. K., Maeng, H., Song, K., & Kaang, S. (2009). Thermal behaviors of heat shrinkable poly(vinyl chloride) film. Journal of Applied Polymer Science, 112(2), 886-895. DOI: 10.1002/app.29550
3. Bělík, P., Jennings, B., Shvartsman, M. M., & Thomas, C. U. (2009). Modeling the behavior of heat-shrinkable thin films. Journal of Elasticity, 95, 57-77. DOI: 10.1007/s10659-009-9194-4