The paper cups were coated with a wax coating
In addition to polyethylene, paper cups may be coated with bioplastics such as polylactic acid (PLA). PLA is made from plant-based materials, and is renewable. However, the in-use cost of PLA is higher than that of PE. Therefore, PLA-coated cups have limited adoption in the paper coffee cup liner market. In addition, PLA has been shown to contaminate recyclable plastic streams. However, PE-coated paper cups can be recycled.
This blend of polyolefinic resins and calcium carbonate mineral provides an effective barrier that is equivalent to PE. Although the coating does not require significant modifications to existing coaters, it will require a heavy coatweight to achieve barrier properties. This will prevent blocking problems during the converting process.