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Eggshells in Biodegradeable Packaging...

Almost 99 percent of it is made with crude oil and other fossil fuels. Once it is discarded, petroleum-based plastics can last for centuries without breaking down.  As an alternative, some manufacturers are producing bioplastics — a form of plastic derived from cornstarch, sweet potatoes or other renewable plant-based sources — that readily decompose or biodegrade once they are in the ground. However, most of these materials lack the strength and flexibility needed to work well in the packaging industry. And that’s a problem since the vast majority of plastic is used to hold, wrap and encase products. So petroleum-based materials continue to dominate the market, particularly in grocery and other retail stores, where estimates suggest that up to a trillion plastic bags are distributed worldwide every year.


To find a solution, Rangari, Tiimob, and colleagues at Tuskegee University experimented with various plastic polymers. Eventually, they latched onto a mixture of 70 percent polybutyrate adipate terephthalate (PBAT), a petroleum polymer, and 30 percent polylactic acid (PLA), a polymer derived from cornstarch. PBAT, unlike other oil-based plastic polymers, is designed to begin degrading as soon as three months after it is put into the soil.  This mixture had many of the traits that the researchers were looking for, but they wanted to further enhance the flexibility of the material. So they created nanoparticles made of eggshells. They chose eggshells, in part, because they are porous, lightweight and mainly composed of calcium carbonate, a natural compound that easily decays.


The shells were washed, ground up in polypropylene glycol and then exposed to ultrasonic waves that broke the shell fragments down into nanoparticles more than 350,000 times smaller than the diameter of a human hair. Then, in a laboratory study, Rangari and his team infused a small fraction of these particles, each shaped like a deck of cards, into the 70/30 mixture of PBAT and PLA. The researchers found that this addition made the mixture 700 percent more flexible than other bioplastic blends. They say this pliability could make it ideal for use in retail packaging, grocery bags and food containers — including egg cartons.

 

 

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