How to Specify Collation Shrink Film for a Reliable Multipack Line

Collation shrink film may look like a straightforward packaging material, but reliable performance depends on far more than width and thickness. The film, product, sealing system and shrink tunnel all need to work together.

When a specification is incomplete, the symptoms often appear on the line: weak seals, loose packs, distorted products, inconsistent shrink, excessive film use or repeated adjustments between reels. A clear collation shrink film specification gives the manufacturer a better starting point and makes production trials far more useful.

This guide explains the information Stretchband Packaging reviews when developing or matching LDPE collation shrink film for food, drink, household-goods and industrial multipacks.

1. Start with the finished multipack

The correct film begins with the pack that must reach storage, distribution or retail in good condition. Record:

• the product type and material;

• the number of units in each collation;

• the pack arrangement, such as 3 × 2 or 6 × 4;

• the overall pack length, width and height;

• the total pack weight;

• whether the pack is unsupported, tray-supported or pad-supported; and

• how the pack will be stacked, palletised and transported.

A lightweight group of cartons and a heavy unsupported bottle multipack can require very different mechanical performance, even when their outer dimensions are similar.

2. Confirm the wrapping and sealing format

The next step is to understand how the machine presents film around the product. Useful details include whether the line uses a single-wound film, two reels forming an upper and lower web, or another configuration.

Seal position also matters. The film must form a dependable seal within the machine's available temperature, pressure and dwell-time window. Simply increasing sealing temperature can mask an unsuitable film for a short period while creating other problems, including film build-up, burn-through or unnecessary thermal stress.

Where possible, provide the machine manufacturer and model, current line speed, seal-bar arrangement and normal operating settings. A photograph of the threading path and an unused sample from the current reel can also remove ambiguity.

3. Treat width and gauge as starting points

Nominal width and micron are essential, but neither describes the whole film. The specification may also need to account for:

• film density and yield;

• tensile strength and elongation;

• puncture and tear behaviour;

• stiffness and web handling;

• seal performance;

• shrink force and shrink balance; and

• reel winding quality.

This is why a lower-micron film is not automatically a lower-cost solution. If it creates more rejects, damaged packs or stoppages, the saving per kilogram can disappear quickly. The better comparison is cost per accepted pack at the required line speed.

4. Define the shrink result the pack needs

The aim is controlled pack stability, not simply the tightest possible wrap. Too little shrink can leave an unstable or untidy multipack. Too much shrink force can deform lightweight containers, pull apertures out of shape or create excessive tension around corners.

Tunnel temperature alone does not describe the shrinking process. Airflow, exposure time, conveyor speed, tunnel-zone settings, product temperature and pack geometry all affect the finished result. These variables should be recorded during a controlled trial so that film and machine changes are not confused.

5. Check reel construction and line handling

Good film can still perform badly if the reel presentation does not suit the equipment. Confirm:

• reel width and maximum outside diameter;

• core internal diameter and core length;

• maximum reel weight;

• winding direction;

• splice requirements;

• pallet configuration; and

• any reel-handling limitations at the machine.

Consistent winding tension and reel profile help the web track predictably. This becomes increasingly important as line speed rises or film gauge is reduced.

6. Consider print, perforation and pack appearance

Clear film is suitable for many transit multipacks, but printed collation shrink film can add branding, product identification, handling information or promotional graphics. Print registration, ink system, slip and sealing areas should be considered together rather than added after the base film has been approved.

Perforation may be used where the application needs controlled ventilation or easier pack opening. The pattern must be developed around pack strength and line behaviour; excessive or poorly positioned perforation can create weak points.

7. Assess recycled content against the real application

PCR content can be appropriate for selected collation shrink-film applications, but it should be validated against clarity, strength, sealing, shrink response, print requirements and the product's regulatory needs.

UK Plastic Packaging Tax currently applies at £228.82 per tonne from 1 April 2026 to finished plastic packaging components containing less than 30% recycled plastic, subject to the detailed scope, registration rules, exemptions and reliefs in HMRC guidance. Tax treatment should therefore be confirmed for the specific packaging and supply chain rather than assumed from a film description alone.

For household packaging in scope of Extended Producer Responsibility, liable producers may also need to assess and report recyclability using the UK's Recyclability Assessment Methodology. Film selection should form part of the wider pack assessment, not be considered in isolation.

8. Run a controlled production trial

A useful trial has agreed success criteria before the reel reaches the line. These may include:

• stable running at the target packs per minute;

• seal integrity;

• consistent pack dimensions and appearance;

• acceptable shrink around corners and apertures;

• no product distortion;

• controlled start-up and changeover waste; and

• satisfactory pallet and transit stability.

Change one significant variable at a time and retain the settings, film batch details and finished samples. This creates evidence for final approval instead of relying on impressions from a short run.

A better specification reduces avoidable trial work

The strongest collation shrink film specification connects the finished pack, machine conditions, reel construction and commercial objectives. That gives the film manufacturer enough information to recommend a sensible starting structure and helps the production team evaluate it consistently.

Stretchband Packaging supplies bespoke collation shrink film, including clear, printed and selected PCR/recycled film options. Review our collation shrink film range: https://www.stretchbandpackaging.co.uk/collation-shrink-film

For printed requirements visit https://www.stretchbandpackaging.co.uk/printed-films, explore PCR options at https://www.stretchbandpackaging.co.uk/recycled-pcr-polythene, or contact our team for a no-obligation technical discussion: https://www.stretchbandpackaging.co.uk/contact-us