Polyethylene Terephthalate (PET) is commonly marked with resin identification code 1 and the letters PET or PETE. That mark is the best first clue when you are sorting bottles and containers—but it is not proof that an item is recyclable in a particular program, suitable for food contact, or compatible with a buyer’s PET specification.

Reliable sorting uses several layers of evidence. Start with the molded code and the package format, separate obvious contaminants, then verify the polymer with near-infrared (NIR) or laboratory analysis when quality matters. This guide turns that principle into a practical workflow for collectors, reclaimers, converters, and procurement teams.

How to Identify Polyethylene Terephthalate

Look first on the base, heel, or lower sidewall of a rigid package. A number 1 inside the resin identification mark with PET or PETE beneath it indicates the article was made from Polyethylene Terephthalate. Typical examples include water and soft-drink bottles, edible-oil bottles, some household-product containers, and clear thermoformed trays.

Do not rely on appearance alone. PET is often clear, glossy, stiff, and lightweight, but other polymers can look similar. PET also appears in transparent colors, opaque constructions, thermoforms, sheet, strapping, and fiber. The same polymer name does not mean every format belongs in the same recycling stream.

ASTM D7611 defines resin identification codes as a way to identify the resin used in an article. ASTM explicitly distinguishes these marks from recycling codes: the symbol does not guarantee that the item is collected or reclaimable. CBRHK’s guide to food-grade PET compliance makes the related point that a resin code is not evidence of food-contact approval.

A quick identification check

Signal	What it tells you	What it does not prove
Code 1 with PET or PETE	The molded article is identified as PET	Local recyclability, food-grade status, or recycled-content level
Clear, glossy, stiff bottle body	The item has characteristics common to bottle-grade PET	Polymer identity by itself
Bottle, tray, sheet, strap, or fiber format	The likely market and processing route	Compatibility with a specific PET bale or flake grade
NIR or FTIR result	The polymer’s spectral fingerprint matches PET	Color, intrinsic viscosity, contamination level, or end-use approval
Supplier documents and lot data	The declared grade, origin, and specification	Performance unless the material is sampled and tested

For clean production scrap with known traceability, documentation may be sufficient for routine sorting. For mixed post-consumer material, use the code only as a screening tool and build verification into the line.

PET Lookalikes and Contaminants to Remove

The most serious sorting errors often come from materials that resemble PET or remain with PET during washing.

• PVC: Clear PVC can resemble PET, and both materials sink in water. That means float-sink separation cannot reliably remove PVC after granulation. Even small PVC contamination can damage recycled PET during melt processing.
• PETG: PETG is a glycol-modified polyester, not a drop-in substitute for standard bottle-grade PET in a conventional bottle-recycling stream. RecyClass lists PETG as non-compatible in its March 2026 guidance for transparent colored PET bottles.
• PLA, PS, PC, and PBT: These resins may appear in clear rigid packaging or components. They require separate identification and should not enter a PET stream unless the receiving specification expressly permits them.
• Multilayer and specialty PET formats: CPET trays, PET/PE laminates, opaque bottles, and barrier structures can behave differently from clear bottle PET. Separate bottles from thermoforms and other formats at the earliest practical point.
• Labels, sleeves, closures, and metals: A large or heavily printed sleeve can hide the bottle body from an NIR or color sorter. Sinkable labels, metal parts, and adhesive residue can remain with the PET flake and lower its value.

The safest rule is simple: if an item cannot be identified confidently, place it in a quarantine or reject stream rather than guessing. Do not use a flame, burn, odor, or improvised solvent test. Those methods create avoidable safety risks and are too subjective for quality control.

A Step-by-Step PET Sorting Workflow

1. Define the accepted PET grade

Start with the buyer’s written specification. State whether the target is clear/light-blue bottle PET, colored bottle PET, thermoform PET, production scrap, washed flake, or another grade. Define permitted closures, label types, moisture, color, metal, PVC, fines, and non-PET limits.

This step prevents a common failure: producing a technically “PET-rich” bale that does not match the customer’s process. If the material will become bottle-grade or fiber-grade PET, the acceptable feedstock and test limits may differ.

2. Pre-sort by package format and color

Remove bags, films, paper, glass, metal, and visibly contaminated articles. Keep bottles separate from thermoforms unless the off-taker accepts a combined stream. Within bottle PET, separate clear/light-blue material from green, amber, dark, fluorescent, metallic, and opaque articles.

Color is not merely cosmetic. Clear feedstock usually has the widest range of high-value applications, while strong color mixing restricts what the recycled resin can become.

3. Remove items that disrupt mechanical sorting

Use screens and dimensional separation to remove fines and very small items. Air classification can remove films and lightweight label fragments. Magnets and eddy-current systems target ferrous and non-ferrous metals. Manual quality control remains useful before and after automated equipment, especially for hoses, cables, batteries, and unusual packages.

4. Identify polymers with NIR and sort by color

NIR systems illuminate each article and compare the reflected spectrum with known polymer fingerprints. Air jets then direct identified PET into the selected stream. NIST describes infrared spectroscopy as a common commercial method for separating plastics by type, while visible-light systems can further divide clear and colored material.

Give the sensor a clean view of the bottle body. Full-body sleeves, dark surfaces, metallized decoration, stacked containers, and heavy soil can reduce identification accuracy. Use a second-pass or quality-control sorter when the required purity justifies it.

5. Grind only after whole-item contaminant removal

Granulation creates a more uniform feed for washing, but it also makes lookalike contaminants harder to remove manually. Capture PVC, PETG, multilayer items, metals, and problem sleeves while they are still whole and recognizable. Maintain knives, screens, and dust collection so flake size and fines stay within specification.

6. Wash and use density separation

Washing removes product residue, dirt, paper fiber, labels, and adhesive. In a conventional water-based float-sink stage, PET sinks while many PE and PP caps and labels float. This is an effective separation step, but it is not a substitute for polymer sorting: PVC and other dense contaminants can sink with PET.

Control wash chemistry, temperature, residence time, friction, rinsing, and wastewater treatment around the feedstock and end-market requirement. For packaging design, APR and RecyClass both favor components that detach cleanly and separate from PET during grinding and washing.

7. Inspect and test the finished flake

Final sorting may combine color cameras, metal detection, optical flake sorting, and manual checks. Sample the finished lot using a documented plan and test the properties that matter to the buyer. These may include:

• PVC and other polymer contamination
• Color distribution, black specks, and visible foreign matter
• Metals, glass, label, glue, and paper
• Moisture, bulk density, fines, and flake-size distribution
• Intrinsic viscosity, melt behavior, and food-contact evidence when applicable

ASTM’s plastics-recycling standards include methods for PVC contamination in PET flake and techniques for separating and identifying contaminants. A passing result should be linked to the bale or lot, production date, source stream, line settings, and corrective-action record.

Manual vs. Automated PET Identification Methods

Method	Best use	Strength	Limitation
Molded code and package inspection	Collection, receiving, and presort	Fast and inexpensive	Missing codes, misleading appearance, and no purity data
Supplier declaration and traceability	Known industrial scrap or virgin resin	Connects material to a grade and lot	Depends on source control and document integrity
NIR spectroscopy	High-throughput whole-item sorting	Rapid, non-destructive polymer identification	Surface coverage, dark color, soil, and multilayers can interfere
Visible/color camera	Clear-versus-colored sorting and defect removal	Protects clear-feedstock value	Does not confirm polymer identity
Float-sink separation	Washed flake and component separation	Efficiently separates dense PET from many PE/PP parts	PVC and other dense materials may sink with PET
FTIR or DSC laboratory testing	Unknown samples, disputes, and validation	Stronger material confirmation	Slower, sample-based, and requires trained staff

The methods are complementary. Manual inspection catches unusual objects; optical sorting handles volume; washing and density separation clean the flake; laboratory testing confirms ambiguous or high-risk samples.

How to Improve PET Bale and Flake Quality

High purity begins upstream. Train suppliers with accepted-item photos and a short reject list. Audit incoming loads by source, record contamination types, and give specific feedback rather than a single pass/fail score. A supplier that repeatedly sends PVC sleeves needs a different corrective action from one that sends excessive moisture or metal.

Set control limits inside the contractual rejection limits. If the buyer rejects at a given contamination threshold, an identical internal alert threshold leaves no room for sampling variation or process drift. Trend sorter rejects, color yield, PVC detections, wash loss, and finished-flake defects by shift and source.

Avoid universal consumer instructions such as “always remove every cap.” Collection and reprocessing systems differ. Follow the local program and the receiving plant’s specification. At an industrial line, base cap and label handling on whether those components are detected, detached, floated, and captured effectively.

For a documented example of why sorting quality matters, see CBRHK’s 100% recycled PET bottle case study. Its manufacturing checklist connects clean feedstock with bottle-grade quality, food-contact evidence, and traceability.

Common PET Sorting Mistakes

1. Treating every number 1 item as accepted. The code identifies resin, not the rules of a local program or buyer.
2. Mixing bottle and thermoform PET without approval. Similar chemistry does not guarantee identical collection, processing, or end markets.
3. Waiting until after grinding to remove PVC and PETG. Small flakes are more difficult to identify and separate.
4. Using color as polymer proof. A clear package is not necessarily PET, and PET is not always clear.
5. Ignoring sleeves and decoration. They can hide PET from NIR and color systems or introduce sinkable contamination.
6. Assuming float-sink removes every non-PET polymer. Dense contaminants can follow PET into the sink fraction.
7. Making food-grade or recyclability claims from the resin code. These claims require separate evidence tied to the material, process, intended use, and market.

If line performance is the constraint, compare each stage—opening, screening, ballistic or dimensional separation, NIR, color sorting, grinding, washing, and flake polishing—against the defect found in the finished product. CBRHK’s review of PET recycling machinery brands can help frame equipment discussions, but trials on representative feedstock should decide the final configuration.

FAQs About Identifying and Sorting PET

How can you tell if a plastic is PET?

Look for resin identification code 1 with PET or PETE molded into the article. Use the package format and source as supporting clues. For mixed or high-value material, confirm the polymer with NIR, FTIR, or another validated analytical method.

What is the difference between PET and HDPE plastic?

PET carries code 1 and is commonly used for clear beverage bottles. HDPE carries code 2 and is common in milk jugs, detergent bottles, and other rigid containers. They have different polymer structures and are sorted into separate recycling streams. Appearance alone is not a reliable test.

Does the number 1 mean a PET package is recyclable everywhere?

No. The number identifies the resin. Actual acceptance depends on package format, size, color, local collection, sorting capability, and a viable end market. Check the applicable program or buyer specification.

Can PET be separated from caps and labels by floating?

Often, but only when the components are designed for that process. PET sinks in water, while many PE and PP closures and labels float. PVC, metal, and other dense components can sink with PET, so presorting and component design remain important.

Can PET bottles and PET thermoforms be sorted together?

Only if the receiving facility accepts that mixture. Bottle and thermoform streams can have different collection systems, additives, barriers, labels, adhesives, and end-market requirements. Separate them when the specification calls for it.