TLC from PVC: Vinyl Cushions the Ride From Farm to Supermarket

Sometimes there’s no such thing as a good move. When you’re trucking fresh produce—or jars of pasta sauce—cross-country, you don’t want those loaded pallets to budge. There’s a science to packing and bracing these loads to avoid disastrous shifts, and vinyl is playing a role.

The product is a vinyl dunnage air bag, developed by Centerload Shipping Technologies of Hayward, Calif. (www.centerload.com). “Dunnage” is an old maritime term that originally referred to pieces of wood placed along the sides and bottom of a ship’s hold to keep the cargo dry. Eventually, dunnage came to mean any protective material around shipments, whether by land or by sea.

For years, trucking depended on dunnage air bags made of a polyethylene liner wrapped in multiple layers of kraft paper (these are still preferred for some uses). But these air bags have a number of drawbacks: They are rigid, they tend to rupture under certain conditions, and they can only be used once.

Working with 9.8-mil vinyl sheeting, Centerload built an air bag that is stronger, more flexible, and reusable. Currently, the company sells several million vinyl air bags a year. They fold, cut, and seam the inflatable bags to any size the customer specifies.

Grace Under Pressure

Altitude changes can pose a problem for paper dunnage air bags, explained Centerload’s vice president, Helmut Elze. Once the polyethylene sleeve is inflated, there isn’t much “give” in the outer layers of paper. When a truck travels to higher elevations—over the Rockies, for example—the air in the environment becomes thinner than the air inside the air bags. The air within the air bags expands and can cause a rupture. Burst air bags wreak havoc on cargo. In contrast, Elze said, the vinyl air bags are flexible, respond to changes in pressure, and don’t rupture.

Vinyl dunnage air bags have also made possible a new packing configuration that helps keep produce fresh, he said. Traditionally, pallets are placed against the right and left sides of the truck. The problem is that, even though the area is refrigerated, heat from the outside eventually transfers into the inner walls and affects the produce packed against the walls. Some California growers—with the help of folks at the University of California at Davis—developed and tested the idea of moving pallets away from the sides of the truck. Bracing the pallets is key. Vinyl dunnage air bags fill the 6- to 14-inch space between the wall and the pallets (depending on load configuration) expanding and contracting as needed. Further, the air bags are installed only along the top half of the shelving, leaving the bottom half free for air to circulate.

Preserving Cargo, Money, Environment

Vinyl’s flexibility also means the air bags conform to the shape of the cargo (unlike rigid paper air bags), so the goods are is less likely to be bruised, broken, or bashed, Elze said.

Also, because the vinyl dunnage air bags can be reused a number of times, customers can save hundreds of thousands of dollars a year, and the environment benefits as well, Elze said. Finally, the bags are 100 percent recyclable. Through the Vinyl Institute, Centerload directs its customers to recyclers, who welcome their high-quality PVC.