Canadian Plastics

Bioplastics grow up at Cascades Inopak

By Rebecca Reid, associate editor   

Make sure to tell your kids that just because a new container from Cascades Inopak is made from corn, it certainly doesn't make a tasty afternoon snack....

Make sure to tell your kids that just because a new container from Cascades Inopak is made from corn, it certainly doesn’t make a tasty afternoon snack.

But what you can tell your kids is to chuck these containers into those green bins that have been popping up in more and more municipalities around the country.

That’s because these containers, made from NatureWorks LLC’s corn-based polylactic acid (PLA) polymer, are compostable. That means products made from PLA will break down after being exposed to water and oxygen in less than 110 days, said Patrice Clerc, development market manager at Cascades Inopak in Drumondville, Que., a division of Cascades Canada Inc.

In terms of properties, PLA resembles clear polystyrene, has good aesthetics in terms of gloss and clarity, but is stiff and brittle, and needs modifications for use in most practical applications, said Don Rosato, senior research analyst, plastics at Frost & Sullivan’s Technical Insights Group. Plasticizers, for example, increase the flexibility of PLA, he added.


In Cascades’ experience, PLA packages have better clarity and rigidity compared with polyethylene terephthalate (PET), Clerc noted. Additionally, Clerc says these PLA-based packages are just as strong and durable as the same containers made from PET. However, PET doesn’t biodegrade for decades, Clerc said.

But biodegradability differs from compostability: composting requires the presence of both water and oxygen. As a result, a PLA-based container won’t break down if it ends up air-deprived at the bottom of a landfill. It will eventually break down, but not any faster than most other plastics.

Before the costs of natural gas and oil skyrocketed after hurricanes Katrina and Rita, PLA was more expensive than PET, Clerc said. Now, the cost of each material is about the same. But when oil prices calm down and firms have a chance to replenish their chemical stocks, in about six months, Clerc projects, the cost of PLA will again be higher.

“Currently, bioplastics are about 2.5 to 7.5 times more expensive than traditional major petroleum-based plastics,” Rosato said. “Only five years ago bioplastics were 35 to 100 times more expensive than existing non-renewable fossil fuel-based equivalents.”

But customers don’t mind paying a few cents more for corn-based PLA packaging, Clerc said, because they see the value in marketing their products as “green.”

And, the higher cost of PLA doesn’t negatively impact Cascade Inopak’s bottom line because of some processing advantages of PET offset the higher costs, he said.

Cascades thermoforms packages with PET as well as polystyrene (PS). However, the machines need to be tuned differently for thermoforming each material. But PLA can be thermoformed on a PET line without re-tuning the machinery, Clerc said.

Additionally, Clerc said PLA can be processed at lower temperatures, and produce packages with thinner walls, so less material is needed. Wall thickness can be reduced to 14 mil., with PLA, compared to 16 mil., with PET, he said. These factors further offset the higher cost of PLA resin compared to PET.

However, PLA can’t withstand tem- peratures exceeding 55C, Rosato said.

Clerc said this limitation could pose problems if transporting PLA containers through hot climates, like Texas or Arizona. Moving these items through northern North America, however, hasn’t posed a problem, he said.

The temperature constraints also mean PLA packages can’t be put in the microwave. But an endorsement from Wal-Mart Inc., the world’s largest retailer, means PLA is here to stay.

So far, PLA has been used to wrap items like socks and pants, but Cascades is looking for ways to expand the market, and this container is simply the first step.


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