I am new to the company, and one of the commodities I purchase is stretch film. When I get requests from the plant, they refer to it as shrink film. Are they the same thing?
Hello Toby, thanks for sending in your question. I am glad you asked because many people confuse the two. Spoiler alert – they are not the same thing. Let’s break down the differences between the two films to understand what they are and how they are used.
Stretch film is used to wrap pallets that are ready for shipment. After a pallet is wrapped with stretch film, the film conforms tightly to the shape of the load, so it looks like the film “shrinks” onto the load. Although that observation is logical, it is the source of confusion between the two films. Stretch wrap is designed to be stretched by the wrapping machine as it’s applied to the load. Force is needed to stretch the film, and the further it is stretched, the more force is required to stretch it. After the wrap cycle has finished, that force is removed because the machine is no longer stretching the film. The stretch film will then retract by some percentage, just like a rubber band. When it retracts, it applies a unitizing force around the load, called “Force-to-Load”, just like the force a rubber band applies when you stretch it around an object. This is very important because it is one of the key elements that defines the load’s resistance to failure during transportation. Your company has a load containment standard, and someone in your company audits pallets at a regular interval to measure force, verify the number of wraps, and then cut and weigh the film. So, you will probably hear the term “Force-to-Load” at some point. Typically, the higher the Force-to-Load, the greater the load containment, up to the point when the contents of the load begin to be crushed.
Shrink film is not considered extensible; in other words, it can’t be stretched. However, when heated, it will shrink, typically in one direction, by as much as 75%, and it will shrink in a precise and controlled manner. This film is normally used for bundling a group of products together, such as bottles or cartons, called packs. These packs may be placed in trays or directly onto a pallet, and after that, the pallet is wrapped using stretch film. Shrink bundling contributes to load containment because it limits product movement, one of the reasons loads fail during transportation. Because the shrink rate is tightly controlled, the shrink film can be printed with the graphics elongated such that once heat is applied and the film shrinks, the graphics will end up in the proper proportion with no distortion. Another popular application for shrink film is to form it into a sleeve or tube and slip it over a container, such as a bottle, then, when heat is applied, it shrinks to conform to the contour of the bottle.
To summarize:
Both films change state when an outside energy is applied, mechanical energy in the case of stretch film and heat energy in the case of shrink film.
The films are made from different resins with significantly different properties.
Typically, shrink films are thicker than stretch films.
It’s common to print graphics on shrink film, where printing on stretch film is not practical because the amount of stretch cannot be precisely controlled, the graphics will become too distorted. In addition, when the print is extended, it loses density, making it difficult to see.
Both films contribute to load containment, shrink bundling limits individual component movement, whereas stretch film unitizes and contains all the contents on the pallet (and is the primary source of load containment when a pallet is transported).
I hope that helps clear up the confusion between the films and their respective roles.
Load containment has been a focus of ours for years. We have studied the science behind load failures and used that to develop our patented technology. This technology improves load containment while drastically reducing film usage. Less film on the pallet translates to a decrease in the cost to wrap a pallet to meet your load containment standard. Also, by reducing the number of wraps applied to the pallet, we unlock hidden capacity in your plant by freeing up machine time.
Thanks for asking!
