The Association of Plastics Recyclers
  • PLA

    PLA

PLA (Polylactic Acid, Resin Identification Code #7)

Polylactic acid (PLA) is one of several structures and polymers using resin identification code (RIC) #7. PLA is typically used in applications requiring stiffness, resistance to cracking, clarity and ease of modification. It is easily formed into sheet and is thermoformable. PLA is often chosen as a packaging material because it is made from renewable resources and is compostable in an industrial composting facility. PLA properties can be enhanced with colorants, impact modifiers, and other additives. Each modification to base PLA must be considered for its effect on the recycling stream. This section of the Design® Guide applies to rigid PLA.

At this time, PLA collection systems are limited in North America so this material does not currently meet the collection accessibility criteria established in “APR’s definition of recyclable” or by the Federal Trade Commission (FTC) “Green Guides.” Anticipating the development and growth of future PLA recycling programs, however, the APR recommends the following guidelines.

  • PREFERRED

    PLA and PLA resin variants which have a crystalline melting point between 140C and 170C

    Flake from thermoformed parts, trim scrap, or cast sheet is amorphous. Flake from oriented film or oriented sheet will be a mixture of amorphous or crystalline fractions, while fibers like staple or spunbond are crystalline. Amorphous PLA flake requires drying at low temperatures (43-55oC) to prevent sticking in dryers. It is the process, the shape and degree of crystallinity, and the percentage of regrind that will determine if the recycled PLA material will need to be pre-crystallized prior to drying and melt extrusion. Recycling crystalline PLA material allows drying at temperatures in the range of 65-85oC. Non-crystallized resin and material with a lower melt point may become sticky in the reclaimer’s pre-extrusion dryer and could prevent the material from flowing through the process. Contaminant materials of a higher melting point remain solid in the reclaimers’ extruder, catch on and may cause blockages in melt screens and contamination in the final product.

    The density of PLA is 1.24 g/cm3 and so it sinks in water.

    Recycled PLA Content

    Depending on the application, a blended recipe of post-consumer and post-industrial PLA is encouraged for products up to the maximum amount technically and economically feasible.

  • PREFERRED

    All non-dark colors

    As PLA recovery and recycling is in an early development stage and clear packaging applications are not an initial target for recycled PLA, there is a wider tolerance for pigmented polymer than if a clear packaging application was being pursued for this material. However, lighter colors will have more value and compatibility with a wider variety of end uses.

    DETRIMENTAL

    See "Requires Test Results" section

    REQUIRES TEST RESULTS

    Black and dark colors with L-Value less than 40 or NIR reflectance less than or equal to 10%

    Sortation testing for dark colors will result in either a Detrimental or a Renders Non-Recyclable ruling. Dark colors cannot be Preferred at this time.

    NIR (near-infrared) sorting technology used in MRFs and reclaimers is not capable of identifying many dark polymers since the colorant absorbs light and manual sorting cannot distinguish one dark polymer from another. Other separation techniques such as float-sink cannot be employed since many polymers sink with PLA. Therefore, dark packaging is considered a contaminant for nearly all reclaimers. Some dark shades may be detected by NIR but these must be tested to determine their sortability.

    BENCHMARK TEST

  • PREFERRED

    Items whose dimensions are clearly more 3-dimensional than 2-dimensional (CASS > 20)

    Early in the MRF sorting process, 3-dimensional items (containers) are separated from 2-dimensional items (paper). It is important that they sort property and do not cross-contaminate.

    Items that clearly measure larger than 5 centimeters (two inches) in two dimensions

    Small size boundaries are of concern because the industry standard screen size for Material Recovery Facilities (MRFs) in North America potentially loses materials less than two inches to the residue waste stream. Testing can determine the impact of the size and shape of a container on sortability.

    DETRIMENTAL

    Items greater than 7.5 liters (two gallons) in volume

    Recycling machinery, particularly automatic sorting equipment, is not large enough to accept items larger than 7.5 liters. Because larger containers jam the systems, most MRFs employ manual sortation before the automatic line to remove the large items. These items are recovered in a stream of bulky rigid containers that are sold and processed as polyethylene since the vast majority of bulky rigid items are comprised of this polymer. Other polymers including PLA either negatively affect or are lost by the polyethylene processing.

    REQUIRES TEST RESULTS

    Items more 2-dimensional than 3-dimensional (CASS > 11 but < 20)

    Aside from not being captured in the PLA stream, non-conforming items that are more "flat" can cause contamination in the paper stream. If items are not captured and directed into the PLA stream, they are not recycled. Items should have a minimum depth of two inches for proper sortation.

    *Under Development - Definitive Test: Evaluation of 2D/3D Sorting Potential for Articles (SORT-B-0X) 

    Items smaller than 5 centimeters (2 inches) in 2 dimensions

    The industry standard screen size for North American MRFs potentially loses materials less than 5 cm to the residue waste stream. Testing can determine the impact of the size and shape of a container on sortability.

    BENCHMARK TEST

  • PREFERRED

    PLA closures

    Since these are the same material as the target polymer, they will be recycled with it and add to the material yield.

    Closures without liners, made from polymers with density < 1.0 that float in water; specifically PE and PP
    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 sleeves of polymers with density < 1.0 that float in water

    Because these polymers float, they are most easily separated from the container in conventional separation systems. Additionally, the PLA recycling process may capture floatable polyethylene and polypropylene to create an ancillary stream of marketable material. Care must be taken when modifying the polyethylene or polypropylene to ensure the modifier does not increase the overall density to the point that it sinks.

    Shrink film safety sleeves 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 sleeve are Preferred, as the material will not be introduced into the recycling stream.

    DETRIMENTAL

    Closures and shrink film safety sleeves made of polymers with density >1.0 that sink in water (specifically PS, silicone, nylon, acetal, thermosets)

    These materials are heavier than water and sink in the float-sink tank with PLA. They are extremely difficult to separate from the recycled polymer flake, requiring a costly and inexact polymer flake sorter currently not envisioned in the PLA reclaiming operation.

    Also see "Requires Test Results" Section

    RENDERS NON-RECYCLABLE

    PET and PVC

    PET and PVC sink in the float-sink tank with the PLA and are difficult to remove with other methods, thereby causing contamination in the final product. The recycled PLA process is very intolerable to even minute amounts of PET or PVC.

    REQUIRES TEST RESULTS

    Closures or lidding with metal components

    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.

    Metal contamination is highly undesirable in recycled PLA. Metals create wear in process machinery, increase operation costs and yield loss, and are a primary source of defects in products made with recycled PLA. MRFs and PLA reclaimers use magnets 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.

    BENCHMARK TEST

    Shrink film safety sleeves that are NOT designed to be completely removed before the package can be opened

    If a shrink film safety sleeve is designed such that pieces of it may not detach from the package when opened, the material must be tested to determine its compatibility with PLA recycling. Specifically, such materials should either float and be separated from the PLA, or if they sink, they must be compatible with PLA. Companies that are considering such sleeves and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.

    No test methods currently exist for PLA. However, PET Package Component Sink/Float Evaluation (PET-S-05) may be adapted substituting PLA for PET.

    SCREENING TEST

    Closure valves containing silicone (density and floatability will vary)

    Check valves in spray dispensers or pumps may be made of silicone as an alternative to metals. While polymers are generally preferable to metals, the composition of a silicone part may cause it to be incompatible with PLA recycling. It should float in the sink/float system. Companies that are considering such components and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.

    No test methods currently exist for PLA. However, PET Package Component Sink/Float Evaluation (PET-S-05) may be adapted substituting PLA for PET.

    SCREENING TEST

    Closures, dispenser valves, or springs made of metal

    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.

    Metal is difficult to separate from PLA compared to the preferred closure systems (polypropylene and polyethylene) and adds both capital and operating costs to conventional reclamation processes. Even a small amount of metal left in the recycled polymer stream will block extruder screens in remanufacturing. Large metal items attached to PLA packages may cause the package to be directed to the metal or waste stream in the recycling process, causing yield loss. Small metal components such as spray dispenser springs unravel in the recycling process and blind screens, adding significant cost for removal at the end of the process.

    BENCHMARK TEST

  • 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

    PLA labels

    Since these are the same material as the target polymer they will be recycled with it and add to the material yield.

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

    If a PLA label is not available or suitable, then PP or PE labels are preferred since they float in water and separate from the PLA 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. Minimizing label size is advantageous to both processes.

    DETRIMENTAL

    Paper labels

    The PLA reclamation process involves a hot caustic wash that removes glue and other label components to the levels required to render the RPLA 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 PLA. Paper fibers remaining in the RPLA 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 RPLA contamination. These, although removed when the polymer is melt filtered, carbonize causing the same effect.

    Also see "Requires Test Results" Section

    RENDERS NON-RECYCLABLE

    PET and PETG

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

    PVC

    This material is extremely difficult to remove in the recycling process due to its similarity in density to PLA. The recycled PLA process is very intolerant of even minute amounts of PVC.

    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 recycled PLA can result in contamination.

    *Under Development - Definitive Test: New Delamination 

    Full container sleeve labels

    Full container sleeve labels cover a large amount of the container surface with a polymer that is not the same as the container body. Because of this, a sleeve label designed without considering recycling may cause a false reading on an automatic sorter and direct a PLA container 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 RPLA produced. Sleeve labels that have been found compliant with the APR test protocols should be selected.

    BENCHMARK 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 PLA. Even very thin metallized labels may be identified as metal by the sorting equipment and cause the entire package to be rejected as waste, thereby creating yield loss. If not detected, they pass through the process with the PLA and cause contamination issues in the final product.

    BENCHMARK 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 PLA. However, HDPE Bleeding Label Test (HDPE-S-01) may be adapted substituting PLA for HDPE.

    SCREENING TEST

    Label adhesives

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

    Screening Tests: TBD

  • Barrier layers, coatings, and other additives may be added to PLA bottles and containers to enhance the properties of PLA. Unlike closures or labels, these additions cannot be visually determined to be problematic or potentially problematic for recycling. Therefore, testing is particularly important. APR promotes innovation in the development of new barrier technologies that can be demonstrated by testing to be compatible with recycling.

    PREFERRED

    See "Requires Test Results" section

    DETRIMENTAL

    Optical brighteners

    Like many other additives, optical brighteners are not removed in the recycling process and can create an unacceptable fluorescence for next uses of the recycled polymer containing the brighteners. It is difficult to identify material with this negative effect until extremely late in the recycling process where a great deal of added cost has been imparted into a material of low value due to the additive.

    Also see "Requires Test Results" Section

    REQUIRES TEST RESULTS

    Other barrier materials, additives or coatings

    The APR recognizes that other types of additives may be required for the performance of a particular package but are not addressed in this document. Additives such as de-nesting, anti-static, anti-blocking, anti-fogging, anti-slip, UV barrier, stabilizer and heat receptor agents and lubricants should be tested to determine their compatibility with recycling. Of particular concern are additives which cause the polymer to discolor or haze after remelting since recycled material with poor haze or discoloration is greatly devalued and has limited markets. This is particularly troublesome since it is difficult to identify material with this effect until extremely late in the recycling process where a great deal of added cost has been imparted into the material.

    Test protocol: TBD

  • PREFERRED

    PLA attachments

    Attachments made of the base polymer are recovered and recycled with the base polymer without causing contamination or yield loss, thereby generating the highest value.

    DETRIMENTAL

    Paper attachments

    The PLA reclamation process may use a wash to remove glue and other contaminants to the levels required to render the RPLA 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 final polymer. Paper fibers remaining in the RPLA carbonize when the material is reused causing quality degradation.

    Welded attachments

    A certain amount of a welded attachment cannot be separated from the main polymer in the recycling process. These attachments, even when ground and made of floatable materials, cause contamination and yield loss issues in both cases: when the PLA they are attached to causes the ground section containing both polymers to sink, or when the ground section floats.

    RFID’s (radio frequency identification devices) on packages, labels or closures

    Unless they are compatible with PLA recycling and are demonstrated not to create any disposal issues based on their material content, the use of RFID’s is discouraged as it limits yield, introduces potential contamination, and increases separation costs.

    Also see "Requires Test Results" Section

    RENDERS NON-RECYCLABLE

    PET and PVC attachments

    The use of PET or PVC attachments of any kind on PLA packaging is undesirable and should be scrupulously avoided. This includes thermoforms of PET and PVC that may be visually confused with PLA thermoforms. Very small amounts of PET or PVC can severely contaminate and render large amounts of PLA useless for most recycling applications. In addition, PET and PVC are very difficult to separate from PLA in conventional water-based density separation systems due to similar densities (densities greater than 1.0) that cause both to sink in these systems.

    REQUIRES TEST RESULTS

    Metal, metalized and metal containing attachments

    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.

    Examples include metal foils and metalized substrates that sink in water. In the recycling process these items are either identified and removed along with their PLA component in the early stages, thereby causing yield loss, or they pass into the recycling process causing a contamination issue. Since they are heavier than water they sink with the PLA in the float-sink tank.

    If a metalized attachment causes the PLA bottle to fail sortation testing, the bottle is Rendered Non-Recyclable as it is removed from the stream and discarded. If a metalized attachment passes through sortation, it is considered Detrimental as it contaminates PLA.

    BENCHMARK TEST

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