Perfect Packaging Materials Part 4: CPET

PET plastics are popular for plenty of reasons, not the least of which is their clarity—remember, this is a plastic that you use when you want to show off your product. If you don’t necessarily need something transparent, but you want something strong and resilient, CPET could be exactly what you’re looking for.

CPET stands for crystallizable PET. Normally, crystallizing is the opposite of what you want with PET plastics—it robs the material of its translucency. But with CPET, crystallizing is exactly what you want. When we produce CPET at PI, we do it for products like food trays that need to resist the high heat of an oven or microwave. CPET is the type of plastic you see in TV dinner trays or mobile food services, because it can take the heat.

The CPET Challenge

Just like any other type of plastic, though, you need trained hands to create and thermoform CPET. You have to add a nucleating agent and heat it to the point of crystallization, and once it’s crystallized to the point you want, you use a cold mold to stop the process. Too little crystallization, and your plastic will melt in the microwave. Too much, and it’ll shatter on impact.

Of course, smashing your crystallized plastic against the countertop isn’t a particularly effective way of testing its strength—not to mention all the sweeping you would have to do afterward. Instead, we use a density scale. The more crystallization, the denser the plastic.

Is CPET Right For You?

Because it withstands such high temperatures—as much as 375 degrees Fahrenheit—CPET is the plastic of choice for hot food packaging and kitchen tools like cupcake pans and cake molds. Stronger in high temperatures than PET but a better value than other heat-resistant materials like metal, CPET is always popular with manufacturers that want an attractive, versatile and durable alternative.