We get a lot of questions about water-based coatings that are used and how it works exactly. Are they plastic free? Can they be composted etc. We try to answer some questions below:
Coffee cups with water-based coatings are not plastic free
All aqueous coating formulations used to coat paper cups use a thermoplastic chemistry which dries by evaporative means. The aqueous component evaporates while the remaining solids (plastic) remain behind to form a film. This film is integral to the structure of a paper cup as heat is used to melt the plastic layer in order to form a water tight seal along the seam of the cup. These materials contain plastics and therefore should not claim to be plastic free.
Although paper coffee cups can in theory be recycled with a great deal of time, chemicals and water, they are currently not accepted in the paper recycling stream. Since the plastic is infused in the paper, this thin layer of plastic is difficult to separate from the paper. If one succeeds after a lot of effort, the lower specific gravity of the plastic molecules will be filtered together with the light molecules of the cellulose (paper).
The paper is therefore always contaminated with micro and nano plastics. One solution is to make the molecules of the plastic heavier, making them possible to separate from the cellulose.
Paper coffee cups with water based coating are compostable
There are no cups certified for home compostability yet. Some are industrially certified, which means that they can decompose into components. This includes plastics. The decomposition can only take place under specially defined conditions with regard to temperature, humidity, a certain oxygen level in the air and a bacterial soil activity.
To ensure that there is no risk of contamination of the organic recycling stream, when applying for a valid industrial compost certification, the complete product is tested including paper, coatings, inks and adhesives. Only than a cup can receive the certificate.
An important advantage of applying a water-based barrier coating is the reduction of plastic in the product. Water based coated products can range from < 3% to > 8% plastic, so although less plastic is used compared to conventional plastic coatings, they are not plastic free. PE coated paper coffee cups are usually extruded or laminated with between 8% and 15% plastic of the total weight of the coffee cup.
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