The Association of Plastic Recyclers
  • PS/EPS

    PS/EPS

Polystyrene (PS)

Label selection should be considered carefully to find the solution most compatible with the recycling process that also provides the necessary performance characteristics. At a minimum, labels must be designed so NIR sorting machinery can identify the bottle polymer with the label attached, and labels should use adhesives that release from the bottle. Removing adhesives is a significant component to the cost of recycling so the packages using the lowest quantity of appropriate adhesive are the most compatible.

PREFERRED

Polymer labels with a density < 1.0 that float in water, specifically polypropylene or polyethylene

These materials float in water so they are separated from the rigid PS in the float-sink tank with the closures. Since they are the same general polymer as most of the closures they do not contaminate or devalue this stream. Care should be taken to ensure that any modifiers to the label material do not increase its density above 0.95. Note that these are not removed in the combined recycling process but, instead become a contaminant. Minimizing label size is advantageous to both processes.

Polystyrene labels

PS is the same material as the bottle body, so the label will behave like the bottle, and be recycled along with it.

High melting temperature plastic labels such as PET

These labels sink in the float sink tank if one is employed and remain solid in the PS extruder so they can be removed through filtering.

DETRIMENTAL

Paper labels

The PS reclamation process involves a wash that removes glue and other label components to the levels required to render the RPS usable. Paper, when subjected to these conditions, becomes pulp which is very difficult to filter from the liquid, thereby adding significant load to the filtering and water treatment systems. Individual paper fibers making up pulp are very small and difficult to remove so some travel with the PS. Paper fibers remaining in the RPS carbonize when the material is heated and re-melted, causing quality degradation and a burnt smell to the polymer. Non-pulping paper labels that resist the caustic wash process sink in the float-sink tank, thereby causing RPS contamination. These, although removed when the polymer is melt filtered, carbonize causing the same effect.

Also see "Requires Test Results" Section

RENDERS NON-RECYCLABLE

PVC and PLA

Both materials are extremely difficult to remove in the recycling process due to their similarity in density to PS which causes them to sink in the float/sink tank along with the PS. Both cause severe quality degradation in the final recycled PS stream even in very small amounts.

REQUIRES TEST RESULTS

Laminated label substrate

Labels that break into small, very thin pieces of material are more difficult to manage in the recycling process because they behave erratically in a float-sink tank. Therefore, labels that stay intact are preferred. Carry-over of delaminated labels into the RPS can result in contamination.

*Under Development - Definitive Test: New Delamination Test 

Full bottle sleeve labels

Full bottle sleeve labels cover a large amount of the bottle surface with a polymer that is not the same as the bottle body. Because of this, a sleeve label designed without considering recycling may cause a false reading on an automatic sorter and direct a PS bottle to another material stream where it is lost to the process. Furthermore, some sleeve label materials cannot be removed in the recycling process and contaminate the RPS produced. Sleeve labels that have been found compliant with the APR test protocols should be selected.

DEFINITIVE TEST

Metal foil, metalized and metallic printed labels

Sortation testing for metal components will result in either a Detrimental or a Renders Non-Recyclable ruling. Metal components cannot be Preferred at this time. Sorting equipment in the recycling process is designed to detect and eliminate metal from PS. Even very thin metallized labels may be identified as metal by the sorting equipment and cause the entire bottle to be rejected as waste, thereby creating yield loss. If not detected, they pass through the process with the PS and cause contamination issues in the final product.

DEFINITIVE TEST

Label structures that sink in water because of the choice of substrate, ink, decoration, coatings, and top layer

The reclaimers rely on float-sink systems to separate non-PS materials. Label components that sink with the PS end up in the RPS stream as contaminants. No test methods currently exist for PS. However, PET Package Component Sink/Float Evaluation (PET-S-05) may be adapted substituting PS for PET.

SCREENING TEST

Pressure sensitive labels and adhesives

Pressure sensitive labels generally require complete adhesive coverage which is greater than other typical label methods. This raises the importance of the compatibility of the type of adhesive with the recycling process. Adhesives resistant to washing in the recycling process allow labels to remain on the container and become contaminants in the final product. Adhesives that have been found compliant with the APR test protocols should be selected.

Screening Test: TBD

Direct printing other than date coding

Historically, inks used in direct printing tend to bleed or otherwise discolor the polymer during the recycling process or introduce incompatible contaminants. In either case, the value of the recycled polymer is diminished. Some inks used in direct printing do not cause these problems. The specific ink must be tested to determine its effect.

No test methods currently exist for PS. However, HDPE Bleeding Label Test (HDPE-S-01) may be adapted substituting PS for HDPE.

SCREENING TEST

REQUIRES TEST RESULTS

Label adhesives

Adhesives that wash off cleanly from PS and remain adhered to the label are preferred. Label adhesive that is not removed from PS, or which re-deposits on the PS during the wash step is a source of contamination and discoloration when PS is recycled.

The recycling process is designed to remove reasonably expected contamination from the surface of the container to a degree necessary to render the polymer economically reusable in further applications. In practice, some adhesives are resistant to this process so are detrimental to recycling. In extreme cases, an adhesive and label cannot be separated from the PS/PLA and may render a package not recyclable.

Screening Tests: TBD

Label Inks

Some label inks bleed color in the reclamation process, discoloring the polymer in contact with them and significantly diminishing its value for recycling. Label inks must be chosen that do not bleed color when tested under this protocol.

No test methods currently exist for PS. However, HDPE Bleeding Label Test (HDPE-S-01) may be adapted substituting PS for HDPE.

SCREENING TEST


Expanded Polystyrene (EPS)

Some EPS recycling processes do not remove adhesive. The adhesive travels through the process with the PS and is blended in the final product. The most recyclable packages use the lowest quantity of adhesive that is compatible with PS. Lower adhesive usage reduces processing cost and potential contamination risk.

PREFERRED

Polystyrene labels

PS is the same material as the package so the label will behave like the package and be recycled along with it creating no added contamination or yield loss.

Direct printing

Most direct print inks withstand the standard EPS recycling process and remain on the package. Since no adhesive is used and the weight percent of label is extremely low compared to alternative labeling, they add little contamination to the final product.

High melting temperature plastic labels such as PET

These labels sink in the float sink tank if one is employed and remain solid in the PS extruder so they can be removed through filtering.

Also see "Requires Test Results" Section

DETRIMENTAL

Paper labels

Most paper labels remain on the package during the washing phase of the recycling process and enter the extruder with the PS. Paper degrades in the extruder emitting a burnt smell into the plastic that cannot be removed. Most of the paper can be filtered from melted PS but the smell and small individual fibers remain.

Polypropylene and polyethylene labels

Like most labels, PP and PE labels remain on the package during the washing phase of the recycling process and enter the extruder with the EPS. They will also float along with the EPS in a float/sink separation tank. Both PE and PP are liquid at the operating temperatures of the EPS extruder and cannot be removed by a filter. They contaminate the final EPS.

Also see "Requires Test Results" Section

RENDERS NON-RECYCLABLE

PVC

Float sink tanks are not perfect machines. Even though PVC sinks and the EPS floats small amounts of PVC travel with the EPS. The recycled EPS stream is very intolerable to even minute amounts of PVC since it degrades quickly at EPS processing temperatures, erodes machinery and creates a safety risk. Small pieces of PVC render large amounts of the finished product unusable.

REQUIRES TEST RESULTS

Metal foil labels

Metal detectors are employed in the recycling process to protect machinery. Even thin metal foil labels may be identified by detectors and cause the entire package to be rejected as waste, thereby creating yield loss. If not detected, they pass through the process with the PS and cause contamination in the extrusion process. Since they remain solid in the extrusion process they can be filtered from the melted polymer which is advantageous over other materials that melt.

BENCHMARK TEST

Label adhesives

Most adhesives will remain on the package during the EPS washing process and enter the extruder with the PS. Adhesives should either remain solid so they can be melt filtered from the PS or be compatible with PS.

Definitive Test: TBD

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