A PET bottle cap has a mass of around two to three grams. They can be manufactured using injection moulding technology. Most caps are manufactured through this process.
The bottle cap value chain has been strengthened with recent EU legislation, which includes mandatory recycled content obligations. This means that bottles have a variety of recycling paths. For instance, the "Preserve Gimme 5" program recycles caps.
The plastics recycling industry advises consumers to remove their caps before bringing them to the materials recovery facility. Unfortunately, small caps are often lost in the recycling process. These caps may end up in landfills or incineration. However, redesigning the plastic cap could offer a way to create more circular design strategies.
Polyolefin cross-contamination is a significant challenge for recycling facilities seeking to pursue high quality recycling paths. Caps are often a key contributor to this cross-contamination, as they contain slip agents.
Slip agent additives are commonly found in a wide range of plastic caps, regardless of the base polymer. Among the most commonly used are erucamide and behenamide, which are both on the Union's list of authorized plastics additives.
Whether or not these additives were present in the recyclate formulations is important for recycling. Erucamide has been shown to be more susceptible to oxidation. If bottle cap recyclate formulations are not well suited for food contact applications, recyclate manufacturers may not be able to use them to manufacture food contact approved polyolefin recyclates.
Plastic bottle cap recyclate formulations can be obtained from a number of commercial sources. They are analyzed by infrared spectroscopy and differential scanning calorometry.
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