By Pan Demetrakakes, Editor

When it comes to unitizing materials, the “paper or plastic” question is getting more interesting.

If you needed to unitize cans or other rigid primary containers, your only alternatives for a long time were paperboard carriers and flexible plastic rings. The latter had certain disadvantages: they often weren’t as stable as paperboard, they couldn’t carry messages, and they took a beating on environmental grounds.

Paperboard carriers and plastic rings are still the most popular choices for container unitizing. But technical advances in materials, demands by customers like club stores, and the sustainability movement have all inspired developments in polymer-based unitizing options.

The continued rise of club stores has sparked interest in unitizing, especially in current bad economic times, when consumers look for bargains. Bundling two or more containers, even relatively large ones, is a easy way to satisfy the store’s need for an extra-large SKU while avoiding an investment in a bigger primary container.

A big job

Plastic carriers for large, heavy packages need to be sturdy.

“Since we’ve been doing handles, people come to us for the same basic reason,” says Amie Thomas, marketing manager at PakTech, a supplier of unitizing handles. “It doesn’t have to be a trendy reason, but it seems to be just another method of unitizing products. Ours is the only injection-molded handle.”

PakTech handles can go on containers that run the gamut from single-serve containers to family sizes like 2-liter beverage bottles. As injection-molded plastic, they’re sturdier than the standard flexible ring. They also offer the option, with cans, of more protection.

“We have a model available that covers the majority of [the can], and then we have a model that fully covers the can top to provide dirt and bacterial protection,” Thomas says.

PakTech handles are made of injection-molded high-density polyethylene (HDPE), which can be recycled easily. Their minimal coverage means minimal material, which is another “green” advantage. This also means the primary container gets shown off more effectively, which is an important consideration for packagers who have invested in making their containers look good.

“They could look for a billboard if they want to show off their bottles or labels,” Thomas says. “Say, the liquid color, or the shape of the bottle, or they have a great big label that they want to show off, or the cap is pronounced, then they would like our handle because it shows off their primary package.”

Message on film

On the other hand, sometimes packagers who are bundling two or more containers want to take the opportunity to include a message. That’s when bundling with shrink or stretch film becomes an attractive option.

Film bundling has certain advantages over ring or rigid-material unitizing. For one thing, it can unitize containers of two different sizes, which would be useful for products in small containers like flavorings or samples.

Label converter Gilbreath has a dual-seam product for such applications that essentially has two pockets. “The sleeves can be different sizes as far as the lay-flat goes, so you could have a very small container next to a very large container,” says Theresa Sykes, Gilbreath’s director of commercial development. “The limitation is on cut height-it has to be the cut height of the smaller container.”

This kind of bundling can be done with clear film, of course. But suppliers of film and the equipment that applies it say that in most such applications, packagers want printed film.

Not only does shrink or stretch film allow billboarding, but it can take away the need to have the primary containers facing front.

“When you put a clear sleeve on...you would have to orient those containers because you want the front facing a certain position,” says Gary Tantomonico, vice president of operations for PDC International, a supplier of application equipment. “Some select a printed sleeve because there’s really no way of orienting a round container.”

PVC and alternatives

Polyvinyl chloride (PVC) has been the dominant material for such applications, mostly because of its low cost.

“Typically, the customer is looking to get away with a cheap alternative, and PVC is still a cheaper alternative than a PETG [polyethylene terephthalate glycol] or other types of films out there,” Tantomonico says.

However, printed bundling material has to be smooth, without any “smiles” or other wrinkles. That’s when alternatives to PVC start looking good, Tantomonico says: “When using a printed sleeve, you want it to be uniform, flush on the bottom of the container, so you tend to use a better grade of film.” PETG would be such an alternative, along with oriented polystyrene (OPS) and some grades of polylactic acid (PLA), he says.

One way to eliminate wrinkles is to eliminate heat. Polyethylene (PE) stretch film can do that, because it’s snapped over the containers without the need for shrinking, Tantomonico says. PDC’s application equipment typically uses twin timing screws to hold the containers together tightly while the sleeve is being applied.

PVC has another strike against it, Sykes says: “Because of the sustainable efforts, PVC is a no-no, so a lot of these combo packs are choosing PET.”

The use of alternatives to PVC is in line with the general push to present film bundling as a sustainable alternative.

“Retailers are pushing [for packaging] to be sustainable and to reduce the weight of those products, and also to get rid of things like cardboard boots and extras,” Sykes says. “That has been a real plus for sleeves. Because we can print on the sleeve, we can get rid of some of those things.”

As with many other aspects of packaging, another sustainable strategy is downgauging. Specifically, customers are asking for film that’s 2 mils thick instead of 3.

“I think that was actually a preconceived notion that if you had a heavier product, you had to have a 3-mil material,” Sykes says. “But we have found that, even with very heavy food products like rice, 2-mil still holds up fine.”

Packagers who want to unitize primary rigid packages, for club stores or regular retail applications, have options that can address all kinds of concerns and desires. Judicious choice can give a little extra boost to a primary package.  F&BP