Scientists at the University of Waterloo in Canada have developed a coating free of conventional plastic for disposable cups. The material is designed to replace the thin plastic film on the inside of paper cups, which keeps liquids contained but can release microparticles when in contact with hot drinks.
The new coating is made from cellulose acetate – a plant-based bioplastic reinforced with cellulose nanocrystals. The findings were published in the journal ACS Sustainable Chemistry & Engineering of the American Chemical Society.
Paper cups are usually lined on the inside with petroleum-based plastic film. Without it, the cardboard would quickly become soggy. During prolonged contact with boiling water, however, the conventional layer can begin to break down and release particles and phthalates – substances that can disrupt hormonal balance.
The plant-based layer remains intact
The team examined cups with a conventional plastic coating and with the new material under a microscope. The standard film began to peel away from the inner layer, while the plant-based coating remained intact under the same conditions.
“It was a real revelation to discover how easily some plastic coatings release particles,” says the study’s leader and chemistry professor Shirley Tang.Tests showed that the new material does not break down during prolonged contact with boiling water, cooking grease and solvents. Tang describes creating a durable protective layer without conventional plastic as a challenge for the team.
Easier cup recycling
The coating can also be applied to very thin paper, including material with a density comparable to that of household paper towels. This creates the possibility of producing cups with lower raw-material consumption and a lower cost.
The material is biodegradable. Since both the coating and the paper are made of cellulose, there is no need to separate a plastic layer before recycling them. In widely used cups, the plastic and paper are bonded together, which makes processing more difficult and is why a large proportion of them are not recycled.
The researchers see potential for the coating to be used in other types of food and beverage packaging as well. For now, the development is a laboratory alternative to conventional plastic linings, and its adoption in mass production will depend on further testing and technological adaptation.
Sources: bta.bg, the-independent.com