Packaging Corner: Plastic strapping on the rise

Strapping unitizes bundled loads of products—from construction materials like lumber and brick, to primary packaging containers, including beverage bottles and cans. Applied by hand or with machinery, strapping is joined with a metal seal or seal-less joint at the point of overlap to secure the load.

A big trend in strapping is the transition from steel to plastic, according to “Strap Guru” Larry Ruud, process improvement manager for ITW/Signode.

“One big reason for the conversion is worker safety,” Ruud says. “While it still hurts to be smacked by a plastic strap, it’s less likely than steel to cut you.”
Plastic strapping also won’t slice into the tires of vehicles driving over it. In addition, coils of steel strapping are substantially heavier, increasing the risk of lifting injuries when handling the material. And, plastic strapping has more footage on each coil, which means fewer coil changeovers.

Cost is also an advantage, Ruud adds. “In a 1:1 conversion from steel to plastic strapping, packaging costs will decrease,” he says. “That is because the cost-per-foot of plastic strapping is less than steel strapping.”

Although plastic strapping comes in many different types, the most popular is high-strength polyester polyethylene terephthalate (PET), with either a smooth or embossed surface. Regardless of the plastic type, companies considering a switch from steel strapping must consider the break strength and elongation characteristics of the material, says Ruud.

“Steel strapping does not stretch as much as plastic under tensional loading, nor can it recover as much in length during load contraction and expansion caused by changes in temperature or moisture,” Ruud explains. “If a bundle of lumber unitized with steel strapping loses moisture and shrinks, for example, there’s a greater risk of coring, where individual internal pieces of the load slide out one end.” Tightly applied steel strapping is also more likely to fail on an expanding load, like a pressure-treated lumber bundle.

Although any strapping typically indents the corners of the unitized package, unit or load, plastic does so to a lesser degree than steel because of inherent flexibility, says Ruud. It also does not rust, which might stain the product and can also weaken steel to the point of failure on loads stored outdoors.

Finally, for companies with sustainability initiatives, Ruud points out that PET strapping is recyclable, while steel is not. “Our company offers a closed-loop recycling program to customers who sell us back their used PET strapping, not only to save money, but also prevent it from winding up in a landfill.”

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