The Authority on Recyclable Plastic Packaging Design
5
PP Rigid
(Polypropylene)
- Due to its balance of impact, heat and chemical resistance, along with stiffness and close dimensional tolerance, PP is one of the most widely used packaging resins
- PP is easily injection molded, blow molded or thermoformed into a bottle, canister, pail, squeeze tube, tray, tub or closure
- Unlike some other polymers, the versatility of PP allows all components (label, body and closure) of many PP packages to be made of PP.
- The density of PP is 0.90-0.92 g/cm3 and therefore it floats in water
- Polypropylene material is defined using ASTM D4101
Base resin is defined as the polymer makeup of the primary body of the package being assessed.
Blend Density
Density is an important property and float-sink tanks are critical separation tools used by reclaimers. Many fillers, pigments and additives used with PP have higher densities and when incorporated into PP can increase the density of resulting PP blend causing it to sink in the float-sink tank. When a PP item sinks during reclamation, the item is lost as waste reducing yield, increasing cost, and thus will be categorized as non-recyclable. The density of an item can be calculated or measured via ASTM D792, ASTM D1505 or ISO 1183-1.
Adding colorant to packaging can impact NIR sortation and color, which both impact the disposition and value of the final recyclate.
L value > 40 or average NIR reflectance is > 10%
APR Design Preferred
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RES-SORT-01 Near Infrared (NIR) Sorting in the Plastics Recycling Process
L value < 40 or average NIR reflectance is < 10%
Requires Testing
L values ≤ 40 or an average NIR reflectance ≤ to 10% have a high probability of not being recognized by NIR correctly and the packaging will either be sent to the wrong plastic resin stream creating contamination or be sent to a waste stream and not recycled. SORT-EE-01 is a screening test used early on in packaging design to obtain a preliminary evaluation of NIR sortation potential prior to performing more robust testing using SORT-S-01.
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SORT-EE-01 Early Evaluation of the Near Infrared (NIR) Sorting Potential of a Whole Plastic Article
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SORT-S-01 Evaluation of the Near Infrared (NIR) Sorting Potential of a Whole Plastic Article
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RES-SORT-01 Near Infrared (NIR) Sorting in the Plastics Recycling Process
Volume, size and shape of package are important features in determining the impacts on the recycling stream. For that reason, this section splits out volume (Large Size Boundary), size (Small Size Boundary) and shape (2D/3D Boundary) based on sortation steps within the recycling process.
Large Size Boundary
This boundary exists due to size limits of recycling machinery, particularly automatic sorting equipment, within a Material Recovery Facility (MRF). MRFs typically employ manual sortation before the automatic sort line to remove larger items.
≤ 7.5 liters (2 gal) in volume
> 7.5 liters (2 gal) 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.
Small Size Boundary
This boundary exists due to the minimum sieve size within the glass screens at a MRF. The mixed material that enters the MRF to be sorted is first compressed/crushed and then passed over these glass screens. The glass screens have small sieve openings where the crushed glass drops through and is sent to the glass recycling stream. However, small plastic packaging items that are below these sieve openings in the glass screens will also drop through to the glass stream and will be lost to the plastic recycling streams.
> 2 in (5 cm) in any two dimensions
≤ 2 in (5 cm) in any two dimensions
The industry standard glass screen size for North American MRFs potentially loses materials less than 5 cm (2 in) to the glass stream. Sortation testing can determine the impact of the size of a container on sortability.
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SORT-S-02 Evaluation of the Size Sorting Potential for Articles with at Least 2 Dimensions Less than 2 Inches
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RES-SORT-02 Size Sorting in the Plastics Recycling Process
2D/3D Boundary
This boundary exists due to the separation process that happens in a Material Recovery Facility in order to separate out the paper (2D items) from the containers (3D items) within the stream of mixed materials. If plastic packaging is sorted by the machinery as 2D, it will be sent to the paper stream and will be lost to the plastic recycling stream.
Smallest uncompressed packaging dimension ≥ minimum dimensions per RES-SORT-05
Smallest uncompressed packaging dimension < minimum dimensions per RES-SORT-05
While weight and surface area factor into the likely outcome for 2D/3D separation process, the most critical factor is height of the package when it is laying down. Packages tend to orient themselves so that height is defined as the smallest overall dimension of the package. RES-SORT-05 should be used to determine if the packaging needs further testing based on dimensions.
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SORT-S-05 Evaluation of the Two Dimensional/Three Dimensional (2d3d) Sorting Potential of a Whole Article
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RES-SORT-05 Determining Packaging Dimensions that Require 2d3d Sortation Testing
Closures, Closure Liners and Safety Seals should be made from materials that do not negatively impact the final recyclate quality. Material can either be compatible with the base resin or separate in the sink/float process from the base resin. APR recommends caps/closures remain attached to the package when entering the recycling stream. See APR Caps On FAQs.
Polyolefin Closure
PP Polymer Closure
Since polypropylene is the same polymer as the package body, closures and dispensers made of it will be captured and processed with PP. This increases the reclaimers yield and reduces possible waste.
PE Polymer closure with total PE content < 10% of total package weight
An allowance of PE up to 10% of total package by weight reflects that the PP recycling stream routinely contains PE and reclaimers can manage and accept some PE content in the PP stream with minimal impacts.
PE polymer closure with total PE content ≥ 10% of total package weight
When blended with PP, PE material exceeding more than 10% of total package by weight can negatively affects the impact properties and can render the material brittle.
Non-polyolefin Closure
Polymer density > 1.0g/cm3 and sinks in water per O-S-01
Polymers with density greater than 1.0 g/cm3 are expected to sink in the float-sink tank, thereby separating and not impacting the recycled PP.
Contains any amount of PVC material
PVC is relatively easy to remove in the float-sink tank since it sinks while the PP floats. However, the float-sink tank is imperfect and even a very small amount of PVC with the recycled PP renders large amounts of it unusable as the PVC degrades at lower temperatures than those at which PP is processed.
Made with a polymer of density > 1.0 g/cm3 and floats in water due to foaming per O-S-01
Material with density >1.0 g/cm3 that floats in water (due to foaming) and passes through the float-sink tank along with the PP is difficult to remove with other methods and can cause contamination if not compatible with PP material. Testing using PP-CG-01 will verify the impact.
Metal Lidding or Closure
Requires Testing
Some metal components may be of sufficient size to either cause rejection at a metal detector, or steel closures may cause a package to be removed by a magnet. In these cases, the package is sent to a waste stream and not recycled. If a metal closure does not impact metal detectors or magnets, it is categorized as detrimental because metals create wear in process machinery, increase operation costs and yield loss, and are a primary source of defects in products made with recycled PP.
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SORT-S-03 Evaluation of Sorting Potential for Plastic Articles Utilizing Metal, Metalized, or Metallic Printed Components
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RES-SORT-03a Metal Sorting in the Plastics Recycling Process
Polyolefin Liner/Safety Seal
Made with EVA/TPE
EVA and TPE float in water and will not be separated in the recycling process. However, they are compatible with PP and in fact enhance its properties so they are preferred.
PE polymer closure liner/safety seal with total PE content < 10% of total package weight
An allowance of PE up to 10% of total package by weight reflects that the PP recycling stream routinely contains PE and reclaimers can manage and accept some PE content in the PP stream with minimal impacts.
PE polymer closure liner/safety seal with total PE content ≥ 10% of total package weight
When blended with PP, PE material exceeding more than 10% of total package by weight can negatively affects the impact properties and can render the material brittle.
Removable Closure/Liner/Safety Seal
Design to be completely removed from package before opening
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.
Non-Polyolefin Liner/Safety Seal
Polymer density > 1.0g/cm3 and sinks in water per O-S-01
Polymers with density greater than 1.0 g/cm3 are expected to sink in the float-sink tank, thereby separating and not impacting the recycled PP.
Contains PVC Material
PVC is relatively easy to remove in the float-sink tank since it sinks while the PP floats. However, the float-sink tank is imperfect and even a very small amount of PVC with the recycled PP renders large amounts of it unusable as the PVC degrades at lower temperatures than those at which PP is processed.
Made with a polymer of density > 1.0 g/cm3 and floats in water due to foaming per O-S-01
Material with density >1.0 g/cm3 that floats in water (due to foaming) and passes through the float-sink tank along with the PP is difficult to remove with other methods and can cause contamination if not compatible with PP material. Testing using PP-CG-01 will verify the impact.
Liner/Safety Seal containing Aluminum or Paper
Detrimental to Recycling
These materials will contaminate wash water, will contribute to waste disposal costs, or will stick to the valuable PP and reduce quality and value of the final products.
Spray Dispensers and Pumps should be made from materials that do not negatively impact the final recyclate quality. Material can either be compatible with the base resin or separate in the sink/float process from the base resin.
Polyolefin Dispenser/Pump
Made with polyolefins and or polyolefin copolymers including TPO, EVA and TPE elastomers that float in water per O-S-01
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O-S-01 Polyolefin Packaging Articles Sink or Float Evaluation
Non-Polyolefin Dispenser/Pump
Made with a polymer of density > 1.0 g/cm3 and sinks in water per O-S-01
Polymers with density greater than 1.0 g/cm3 are expected to sink in the float-sink tank, thereby separating and not impacting the recycled PP.
Contains any amount of PVC material
PVC is relatively easy to remove in the float-sink tank since it sinks while the PP floats.However, the float-sink tank is imperfect and even a very small amount of PVC with the recycled PP renders large amounts of it unusable as the PVC degrades at lower temperatures than those at which PP is processed.
Made with a polymer of density > 1.0 g/cm3 and floats in water due to foaming per O-S-01
Material with density >1.0 g/cm3 that floats in water (due to foaming) and passes through the float-sink tank along with the PP is difficult to remove with other methods and can cause contamination if not compatible with PP material. Testing using PP-CG-01 will verify the impact.
Contains silicone
Sinks in water per O-S-01
Silicone that sinks in water can be separated out in the sink/float process and therefore not impact the recycled PP stream.
Floats in water per O-S-01
Silicone that floats passes through the float-sink tank along with the PP and is difficult to remove with other methods and can cause contamination if not compatible with PP material. Testing using PP-CG-01 can determine the impact
Contains Metal
Requires Testing
Some metal components may be of sufficient size to either cause rejection at a metal detector, or steel closures may cause a package to be removed by a magnet. In these cases, the package is sent to a waste stream and not recycled. If a metal closure does not impact metal detectors or magnets, it is categorized as detrimental because metals create wear in process machinery, increase operation costs and yield loss, and are a primary source of defects in products made with recycled PP.
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SORT-S-03 Evaluation of Sorting Potential for Plastic Articles Utilizing Metal, Metalized, or Metallic Printed Components
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RES-SORT-03a Metal Sorting in the Plastics Recycling Process
Barriers, Coatings, Additives and Layers are materials added to to the base resin to improve performance such as enhancing the appearance or processability of a package.
Workhorse Additive
Workhorse additives commonly used that have not been shown to cause significant issues with the recycling process or further uses of the recycled PP are: Thermal Stabilizers, UV Stabilizer, Nucleating Agents, Antistatic Agents, Lubricants, Fillers, Pigments, Impact Modifiers and Chemical Blowing Agents.
Workhorse Additive where PP blend density is ≤ 0.97 g/cm3
PP blend density is > 0.97 g/cm3
Some workhorse additives used with PP have higher densities and when incorporated into PP can increase the density causing it to sink in the float-sink tank. When a PP item sinks during reclamation, the item is lost as waste, reducing yield and increasing cost for the reclaimer. Density of PP blend with additives exceeding 0.97g/cm3 should be tested using PP-CG-01 to determine impact.
EVOH
Ethylene Vinyl Alcohol copolymer (EVOH) is a common layer material used to increase the barrier properties of PP packaging. It is not separable in the recycling process and therefore will become part of the recycled PP. Maleated polyethylene (PE-g-MAH) tie layers are commonly used in combination with EVOH to improve the adhesion between PP and EVOH and have been shown to improve compatibility during the recycling process.
EVOH ≤ 6.0 wt% + PP-g-MAH tie layers with MAH > 0.1 wt% and EVOH:tie layers ratio ≤ 2
EVOH > 6.0 wt% + PP-g-MAH tie layers with MAH > 0.1 wt% and EVOH:tie layers ratio ≤ 2
EVOH > 1% with any other tie layer
Additives/Barriers with Density > 1.0 g/cm3
PP blend density is ≤ 0.97 g/cm3
PP blend density is ≥ 1.0 g/cm3 or
< 51 wt% of PP blend floats per O-S-01
< 51 wt% of PP blend floats per O-S-01
Density is an important property and float-sink tanks are critical separation tools used by reclaimers. Many additives and barriers used with PP have higher densities and when incorporated into PP can increase the density causing it to sink in the float-sink tank. When a PP item sinks during reclamation, the item is lost as waste reducing yield, increasing cost, and thus will be categorized as non-recyclable.
PP blend density is > 0.97 g/cm3 and < 1.0 g/cm3
Many additives used with PP have higher densities and when incorporated into PP can increase the density causing it to sink in the float-sink tank. When a PP item sinks during reclamation, the item is lost as waste, reducing yield and increasing cost for the reclaimer. Density of PP blend with additives exceeding 0.97 g/cm3 should be tested using PP-CG-01 to determine impact.
Optical Brightner
Detrimental to Recycling
Optical brighteners are not removed in the recycling process and can create an unacceptable fluorescence for next uses of recycled PP. 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.
Non PP Barrier/Coating
Requires Testing
Some Non PP layers and coatings have been found compatible with PP or are easily separated in conventional recycling systems. Testing must show that layers and coatings will either separate and be removed from the PP in the recycling process or have no adverse effects on the recycled PP in future uses. When used, their content should be minimized to the greatest extent possible.
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SORT-EE-01 Early Evaluation of the Near Infrared (NIR) Sorting Potential of a Whole Plastic Article
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PP-CG-01 Critical Guidance Protocol for PP Rigid Containers
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RES-O-01 Squeeze Tubes Resource
Degradable Additives
Renders Package Non-Recyclable
See APR Position Paper on Degradable Additives
Labels can interfere with automated sorting as well as impact the quality and quantity of the final recyclate. It is important to consider all aspects of a label such as Surface Area, Substrate, Metal Decoration, Inks and Adhesives when selecting a label.
Surface area coverage is defined as the area of the label divided by the area of the side wall and shoulder of the container. The area of the neck ring, threaded finish and base are not included in the area calculation. The surface coverage area of a label can impact whether or not a package can successfully sorted by NIR and color optical sorters. Label surface area coverage, in conjunction with with substrate, metal decoration, inks and adhesives must be considered when selecting a label.
Volume ≤ 550ml
≤ 55% Surface Area Coverage
Containers with labels within the APR Design Preferred surface coverage area are expected to sort accurately in both NIR and color optical sorters.
> 55% Surface Area Coverage
Labels with high surface area coverage may interfere with NIR detection of the PP article. SORT-S-01 determines if the PP article can be recognized and sorted properly to the PP stream. For more information on early evaluation testing for NIR sortation of packages see RES-SORT-01.
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SORT-S-01 Evaluation of the Near Infrared (NIR) Sorting Potential of a Whole Plastic Article
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RES-SORT-01 Near Infrared (NIR) Sorting in the Plastics Recycling Process
Volume > 550mL
≤ 75% Surface Area Coverage
Containers with labels within the APR Design Preferred surface coverage area are expected to sort accurately in both NIR and color optical sorters.
> 75% Surface Area Coverage
Labels with high surface area coverage may interfere with NIR detection of the PP article. SORT-S-01 determines if the PP article can be recognized and sorted properly to the PP stream. For more information on early evaluation testing for NIR sortation of packages see RES-SORT-01.
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SORT-S-01 Evaluation of the Near Infrared (NIR) Sorting Potential of a Whole Plastic Article
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RES-SORT-01 Near Infrared (NIR) Sorting in the Plastics Recycling Process
The label substrate, in conjunction with surface coverage area, metal decoration, inks, and adhesives, must must be considered when selecting a label.
Polymer Film Label
Polyolefin film label that floats in water per O-S-01
Polyolefin labels are commonly expected to be PP films or PE film and are compatible with the PP recycling stream
Polymer film label that sinks in water per O-S-01
Polymers with density greater than 1.0 g/cm3 are expected to sink in the float-sink tank, thereby separating and not impacting the recycled PP
Polymer film label that contains PLA or PVC
PVC, when used with an adhesive that does not release in the wash, enters the extruder with the PP where they are incompatible. PVC degrades at PP extrusion temperatures and renders large amounts of the recycled PP unusable. When used with an adhesive that releases in the wash, these labels sink in the float-sink tank where they are removed. But because the float-sink tank is imperfect, and even a very small amount of PVC entering the extruder causes severe quality and yield problems, this material is detrimental.
Non-Polyolefin film label that floats in water per O-S-01
Non-polyolefin material that floats passes through the float-sink tank along with the PP and is difficult to remove with other methods and can cause contamination if not compatible with PP material. Testing using PP-CG-01 will verify the impact
Paper Label
Detrimental to Recycling
The PP reclamation process involves water and agitation. The paper that detaches from the container when subjected to these conditions becomes pulp, which does not sink intact but remains suspended in the liquid, adding load to the filtering and water treatment systems. Paper remaining adhered to the PP travels with the PP to the extruder where the material carbonizes and causes color defects. Even after melt filtering, the burned smell and discoloration remain with the recycled PP thereby negatively affecting its potential reuse.
Metal decoration on labels includes vapor deposited metal films, metal foils, or inks with metallic pigments. Metal decoration content, in conjunction with surface coverage area, substrate, inks and adhesives, must be considered when selecting a label.
Metal Decoration
Label that contain metalized material where surface area ≤ Preferred Surface Area per RES-SORT-03b
Metalized material content on labels below the preferred surface area per RES-SORT-03b are considered preferred.
Labels that contain metalized material that are untested OR do not pass SORT-S-03
Without further testing, metal foils with surface areas above the Preferred Surface Area in RES-SORT-03b are categorized as Non-Recyclable due to a higher probability of being removed by the metal detector during sortation. When packaging is rejected by a metal detector, the package is sent to a waste stream and not recycled.
Labels that contain metalized material where surface area > Preferred Surface Area per RES-SORT-03b
Metalized material content on labels above the Preferred Surface Area specified in RES-SORT-03b need to be tested using SORT-S-03 to verify they are under the spherical equivalent thresholds.
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SORT-S-03 Evaluation of Sorting Potential for Plastic Articles Utilizing Metal, Metalized, or Metallic Printed Components
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RES-SORT-03b Metal Decoration Resource
The label inks, in conjunction with surface coverage area, substrate, metal decoration, and adhesives, must be considered when selecting a label.
Label Inks
Inks that do not contain metal
Any non metallic inks used on labels attached to PP bottles are considered Preferred as the impact of inks within a stream that is already colored is negligible.
For inks that do contain metal see label guidance for Metal Decoration.
Direct Print Inks
Inks that do not contain metal
Any non metallic inks used to print directly on PP bottles are considered Preferred as the impact of inks within a stream that is already colored is negligible.
For inks that do contain metal see label guidance for Metal Decoration.
The label adhesive, in conjunction with surface coverage area, substrate, metal decoration, and inks, must be considered when selecting a label.
Releasing Adhesive
Used on Polyolefin Film Label substrate that floats in water per O-S-01
Polyolefin labels are commonly expected to be PP films or PE films. If the label is designed to separate from the PP container, it is desirable that the label floats so that the label might be recovered for recycle value.
Used on Polymer Film Label Substrate that sinks in water per O-S-01
When used with a releasing adhesive, polymer labels that sink will detach from the PP container in wash and sink in the sink/float process where they can be removed from recycled PP stream.
Used on Non-Polyolefin Label Substrate that floats in water per O-S-01
Because PP flake floats, it is important to avoid using an incompatible polymer label that also floats when combined with PP. If such a label were to enter the extruder alongside the PP, it could lead to yield loss for the reclaimer due to the incompatibility between the polymers.
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O-S-01 Polyolefin Packaging Articles Sink or Float Evaluation
Non-Releasing Adhesive
Used on Polyolefin Film Label Substrate that does not interfere with flake floating per O-S-01
Used on Polyolefin Film Label Substrate that does interfere with flake floating per O-S-01
Polyolefin labels are commonly expected to be PP films or PE films. If the label is designed to remain with the granulate (an adhered or in-mold label) and adhere to the granulate, or is molded in, the label should not interfere with the ability of the granulate to float in water. If the label causes the PP flake to sinks during reclamation, the item is lost as waste, reducing yield and increasing cost for the reclaimer.
Used on Non-Polyolefin Label Substrate
When used with an adhesive that does not release in the wash, non-polyolefin labels enters the extruder where it is blended with the PP. These polymers from label are not compatible with PP and may cause splay or reduce impact toughness for the recycled PP user.
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O-S-01 Polyolefin Packaging Articles Sink or Float Evaluation
Plastic Attachments with Density > 1.0 g/cm3
Does Not Contain PVC materials
Contains PVC materials
PVC is relatively easy to remove in the float-sink tank since it sinks while the PP floats. However, the float-sink tank is imperfect and even a very small amount of PVC with the recycled PP renders large amounts of it unusable as the PVC degrades at lower temperatures than those at which HDPE is processed
Paper Attachments
Detrimental to Recycling
The PP reclamation process involves a wash step that removes adhesives and other components. This process renders paper into a pulp which is very difficult to filter from the liquid, adding significant load to the filtering and water treatment systems. Some of the small individual paper fibers will remain with the PP and carbonize when the material is extruded, causing unacceptable quality degradation
Polyethylene Attachments
PE Polymer attachment with total PE content < 10% of total package weight
An allowance of PE up to 10% of total package by weight reflects that the PP recycling stream routinely contains PE and reclaimers can manage and accept some PE content in the PP stream with minimal impacts.
PE polymer attachment with total PE content ≥ 10% of total package weight
When blended with PP, PE material exceeding more than 10% of total package by weight can negatively affects the impact properties and can render the material brittle.
RFID Tags
Detrimental to Recycling
The use of RFID’s is discouraged as may limit PP yield, introduce potential contamination, and increase separation and waste disposal costs.
Non-PP Attachments
Requires Testing
Testing using O-S-01 determines if the Non-PP attachment will sink in the float-sink tank, thereby separating and not impacting the recycled PP or if it will float with the PP and possibly contaminate the recycled PP. If the attachment floats along with the PP, testing using PP-CG-01 will determine the impact to the recycled PP stream.
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PP-CG-01 Critical Guidance Protocol for PP Rigid Containers
Metal Attachments
Requires Testing
Some metal components may be of sufficient size to either cause rejection at a metal detector, or steel closures may cause a package to be removed by a magnet. In these cases, the package is sent to a waste stream and not recycled. If a metal closure does not impact metal detectors or magnets, it is categorized as detrimental because metals create wear in process machinery, increase operation costs and yield loss, and are a primary source of defects in products made with recycled PP.
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SORT-S-03 Evaluation of Sorting Potential for Plastic Articles Utilizing Metal, Metalized, or Metallic Printed Components
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RES-SORT-03a Metal Sorting in the Plastics Recycling Process
Welded Attachments
Requires Testing
Testing using O-S-01 determines if the Welded attachment will sink in the float-sink tank, thereby separating and not impacting the recycled PP or if it will float with the PP and possibly contaminate the recycled PP. If the attachment floats along with the PP, testing using PP-CG-01 will determine the impact to the recycled PP stream.