Closures without liners, made from polymers with density
The density of PET is 1.38 and so it sinks in water. Since these other polymers float in water, they are most easily separated from PET flake in conventional separation systems. Additionally, the PET recycling process captures floatable PE and PP closures to create an ancillary stream of marketable material. Care must be taken when modifying the PE or PP, with mineral fillers for example, to ensure the modifier does not increase the overall density to the point it sinks.
Closures plus liners made from polymers with density < 1.0 that float in water (specifically PE & PP closures; PE foam, EVA, TPE liners)
Shrink film safety seals of polymers with density < 1.0 that float in water
Since these polymers float in water, they are most easily separated from PET flake in conventional separation systems. Care must be taken when modifying the PE or PP, with mineral fillers for example, to ensure the modifier does not increase the overall density to the point it sinks.
Shrink film safety seals that are designed to be completely removed before the package can be opened
Regardless of material, designs that require complete removal by the consumer of the safety seal are Preferred, as the material will not be introduced into the recycling stream.
Closure liners that are composites of aluminum and paper
These materials will contaminate wash water, will contribute to waste disposal costs, or will stick to the saleable closure material or valuable PET and reduce quality and value of the final products.
Closures and shrink film safety seals made of polymers with density >1.0 that sink in water (specifically PS, silicone, nylon, acetal, thermosets)
The density of PET is 1.38 and so it sinks in water. Polystyrene, silicone, nylon, acetal, and thermoset plastics are plastics that are expected to sink in the float-sink tank with PET and be detrimental to PET recycling. Sinking plastics are not removed from PET, thereby causing contamination in the final product.
The use of PVC closures or closure liners renders the package non-recyclable per APR. PVC sinks and is extremely hard for the recycler to remove, particularly in small pieces. The recycled PET stream is very intolerant of even minute amounts of PVC.
REQUIRES TEST RESULTS
Closures or lidding with metal components
Metal contamination is highly undesirable in recycled PET. Metals create wear in process machinery, increase operation costs and yield loss, and are a primary source of defects in products made with recycled PET. MRFs and PET reclaimers use magnets, eddy current separators and metal detectors to keep packages with metal components out of the process stream. Metal components such as closures or lidding that trigger metal detectors will cause the entire plastic item to be removed from the stream and not recycled. At best, sortation testing will classify such an item as Detrimental to Recycling.