Question from Bill: There are so many stretch films on the market. What is the difference between them, and how do we choose the one that’s right for us?
Hi Bill, excellent question! I’m certain many people are knocking on your door, telling you they offer the best stretch film, but logic dictates they can’t ALL be right. Let’s cut through the sales pitches so you can evaluate options based on what YOU actually need, not just what they’re selling.
Let’s start with you! Stretch film is applied to a load to contain and stabilize it during transportation and storage. Unless you’re simply wrapping a load to keep the dust off, the stretch film has an important job to do. The nature of your product, how it’s palletized, and how it’s transported determine the level of load containment required to ensure your product reaches its destination in the same condition it left your facility. That’s where the process begins. Once you define your load containment target, the next step is to evaluate different stretch films to determine how much film, and of what type, is needed to meet that goal. The amount of film that you need to apply will vary based on its performance characteristics.
It’s crucial to understand that when you select a particular stretch film, what you are really buying is load containment.
The true cost of stretch film is the cost per wrapped pallet that meets your load containment standard; That’s the only metric that allows you to make a fair comparison.
Now, let’s dive into why there are differences among stretch films. It all begins with the resin blend. Even slight variations in the resin can affect a film’s operational characteristics. Beyond that, the process used to extrude a film can result in a significant difference in performance, even with virtually the same resin. Additives such as “cling” also contribute to or detract from performance. A single film manufacturer may offer several stretch films by using different combinations of those three elements. Keep in mind that unless the manufacturer has excellent process control, there can even be a performance variance in the same film from one order to another.
Next, we need to understand how these performance differences play out in real-world conditions. A force is required to stretch the film, and the amount of force will vary over the distance the film is stretched. Initially, very little force is needed. Then, at some distance, the stretch force flattens out, and finally, at a greater distance, the force required increases significantly – until the film fails (breaks). For optimal performance, you need to reach a level of stretch just before the film fails. This is the point where the unitizing force the film applies around the load is at its greatest. The specific resin blend affects this force over distance curve, which in turn affects the load containment that the film can deliver.
To achieve the greatest unitizing force, the elastic property of the film must decrease over the stretch distance, making the film stiffer. However, that necessary stiffness also makes the film more brittle. The more expensive, high-performance films can achieve this type of stretch to the point of stiffness, but the downside of removing elasticity is that the web easily breaks on sharp pallet corners, tier sheets, or box edges. When web breaks happen often, operators invariably decrease the tension of the wrapping machine until the web doesn’t break. This reduces the containment force and subsequently requires that more film be applied.
Typically, stretch film suppliers will tout Ultimate Strength Curves (which is the force over distance curve mentioned earlier). The numbers can look very impressive, but that curve doesn’t factor in real-world conditions like sharp corners or nails that can puncture the film and break the web. If you were wrapping a round drum, which is used in an Ultimate Strength test, you could compare films using this metric. But as you know, wrapping pallets on your floor is a completely different reality. You can compare it to building a boat in your basement; it looks impressive, but if you can’t get it out, it doesn’t serve its purpose.
Our approach was to start with a scientific understanding of load failure and then couple it with the sensibilities of real-world challenges to engineer a load containment solution that increases load containment, eliminates web breaks, and drastically reduces film usage. By incorporating reinforcement filaments into the web, we can provide an unparalleled level of performance. This gives you the best stretch film value per wrapped pallet, which will meet or exceed your load containment standard.
No smoke, no mirrors, no buzzwords, no pressure – just proven performance.
Thanks for asking!
