OCTOBER 28, 2025

Not All “Recyclable” Claims Are Equal: PET Liners vs EPS Shippers Explained

PET – What Is It, and Why It’s Confusing

PET – short for polyethylene terephthalate – is one of the most widely used and recycled plastics in the world. Consumers most often recognize it as the clear, rigid plastic used for water and soda bottles. In that rigid form, PET can be identified easily by municipal recycling systems and is typically accepted in curbside collection across North America.

However, when PET is transformed into soft, non-woven liners or flexible insulation formats, the story changes. These fiber-based PET products may use recycled PET as their feedstock, but their end-of-life pathway is very different from bottles and trays.

This disconnect between the material type (PET) and the physical format (liner) leads to widespread confusion among consumers and brands alike.

Material vs. Format: Why It Matters

Recycling infrastructure is built to recognize form and shape, not just resin codes. At a Materials Recovery Facility (MRF), sorting systems rely on optical scanners, air jets, and conveyor lines calibrated to detect rigid containers. Flexible, textile-like PET liners do not behave like bottles on a sorting line – they flatten, fold, or wrap around equipment. As a result, they are often missed entirely by scanners or treated as contamination.

Caroline E. James, a sustainable packaging specialist, highlighted this problem in a widely discussed LinkedIn post:

| “The MRF optical sorters can’t ‘see’ this material. It behaves more like a plastic bag or textile than a bottle. It doesn’t end up in the PET stream – it ends up in residue.”
— Caroline E. James, LinkedIn 🔗

This observation is echoed by recycling consultants at Defeo Associates, who note that labeling flexible PET liners as curbside recyclable and using the chasing arrows recycling symbol is misleading because most municipalities do not accept it or aren’t able to process it:

| “The public is being told that these products can go into the curbside stream, but the reality is that they will end up in the trash. The material is simply not recoverable through traditional MRF operations.”
— Defeo Associates 🔗  

Why Confusion Persists

The confusion arises because PET resin itself is technically recyclable, but PET insulation formats are not curbside recyclable in most of North America. They are often promoted with recyclability claims based on the resin type, rather than actual collection and recovery realities.

In practice, these liners:

• Are not recognized by optical sorting systems
• Behave like contaminants, clogging or bypassing sorting lines
• Are landfilled or incinerated after MRF residue sorting
• Can undermine consumer trust when “recyclable” claims do not match their curbside experience.

📌 Key Takeaway

| PET liners ≠ PET bottles. The same plastic resin in a different format can have a completely different recyclability outcome. Flexible PET liners are not accepted curbside in most U.S. programs and should not be marketed as such.

How Insulation Materials Differ

Not all thermal packaging materials behave the same way. Even when two options may seem similar at a glance – for example, a PET liner and an EPS shipper — their thermal performance, structural integrity, and end-of-life pathways can vary dramatically.

Understanding these differences is essential for anyone evaluating insulation materials for regulated temperature-sensitive supply chains.

PET Liners: Flexible, Lightweight, and Format-Dependent

PET liners are typically made from non-woven or felted mats of recycled PET fibers. They are designed to line the inside of a corrugated carton, creating a layer of insulation between the product and ambient temperatures.

Because the insulation is flexible, the performance relies on the outer box for structure. There is no rigid wall to create a defined cavity, which can lead to air gaps between insulation panels. The weight of a temperature sensitive payload and refrigerants, such as frozen gel packs, can compress the flexible insulation further reducing the insulative properties. Moisture can also affect some PET liners, particularly those without vapor-barrier films, potentially impacting insulation performance during long transit durations.

Thermally, PET liners slow down heat transfer primarily by trapping air within the fibrous matrix. While this provides some insulation, it typically does not match the low thermal conductivity of EPS foam, especially when considering air gaps and compression which will impact thermal protection and the ability to hold temperature over time and against extreme temperatures. This makes PET liners better suited for shorter transit windows, light weight shipments, or applications with lower thermal risk tolerance.

EPS: Rigid, High-Performance, and Structurally Supportive

Expanded Polystyrene (EPS) remains one of the highest performing, low cost, insultation materials used in temperature assurance packaging. Its closed-cell foam structure creates millions of trapped air pockets that significantly slow heat transfer, delivering excellent thermal performance over time.

Unlike PET liners, EPS containers are self-supporting. The rigid walls form a defined cavity that maintains shape under load, which helps protect the payload and maintain insulation performance even when stacked or exposed to external pressure. EPS is also inherently moisture resistant, maintaining thermal integrity even in humid or condensate-prone conditions.

This combination of high thermal resistance, structure, and moisture stability makes EPS a widely used choice for shipping pharmaceuticals, clinical samples, perishables, and industrial products that must remain within strict temperature ranges.

Biodegradable EPS: Same Performance, Added End-of-Life Pathway

Biodegradable EPS is fundamentally the same material as standard EPS – offering identical thermal performance, structure, and recyclability through the national EPS drop-off network.

The key difference is the inclusion of a biodegradation-enhancing additive that accelerates biodegradation under biologically active landfill conditions. In these environments, the material is engineered to biodegrade up to 90%+ within four years, providing a backup end-of-life pathway if recycling doesn’t occur – without compromising the material’s insulation capabilities.

Insulation Materials at a Glance

*Biodegradation rates based on ASTM D5511 accelerated landfill testing. Actual rates will vary depending on landfill conditions.

📌 Key Takeaway

| PET liners and EPS shippers are not interchangeable. PET liners offer some weight and recycled content benefits but fall short on curbside recyclability and thermal assurance. EPS remains a high-performing workhorse, especially where temperature compliance and structural integrity are non-negotiable, while Biodegradable EPS has the added benefit of accelerated biodegradation in active landfills if recycling isn’t possible.

Chasing Arrows ≠ Curbside Reality: The Policy Lens

When evaluating insulation formats like PET liners versus EPS, it’s not enough to look at thermal performance alone. Sustainability claims – especially recyclability – are increasingly regulated, and packaging decisions must now consider how resin labeling, collection infrastructure, and policy frameworks intersect.

The Chasing Arrows Dilemma

Many PET liner products are marketed with the ♳ chasing arrows symbol, implying recyclability. While this symbol may correctly reflect the resin type (PET), it does not guarantee that the format is accepted curbside.

Municipal recycling systems are designed to sort rigid bottles and containers — not soft, textile-like PET liners. As a result, these products are often missed by optical sorters, miscategorized, or treated as residue destined for landfill or incineration.

Yet, their labeling often gives consumers the opposite impression: that tossing them in the blue bin is the “right thing” to do.

Emerging Regulatory Pressure

This gap between recyclability claims and actual infrastructure is now a focal point for regulators. Two key frameworks illustrate why this matters:

• FTC Green Guides:
  At the federal level, the U.S. Federal Trade Commission’s Green Guides set standards for environmental marketing claims. The Guides specify that companies should not make unqualified recyclability claims unless a “substantial majority” of consumers (60% or more) have access to appropriate recycling programs for that item.
  📄 Read the FTC Green Guides
• California SB 343:
  California has enacted one of the most stringent state laws governing recyclability labeling. Under SB 343, a product cannot display the chasing arrows symbol unless it meets strict criteria -including that >60% of California residents have access to curbside recycling for that specific format. Formats like flexible PET liners currently do not meet this threshold, meaning such labeling may be considered misleading under state law.

ThermoSafe recently explored these regulatory developments in depth in the Cold Chain Exchange article:
USA Packaging Legislation: What Are Your Sustainability Responsibilities?

Policy Meets Packaging

These regulatory shifts have direct implications for packaging selection:

• Resin ≠ Recyclability: Just because something is made from a recyclable resin doesn’t mean it is accepted curbside in its current format.
• Labeling ≠ Reality: Using chasing arrows on non-curbside-accepted materials exposes companies to legal risk and consumer confusion.
• Compliance is Strategic: Selecting materials that align with evolving labeling laws is becoming just as important as selecting for performance or cost.

📌 Key Takeaway

| Just because a product claims to be “made from recyclable material” doesn’t mean it’s actually recyclable curbside. Policy is catching up with marketing language – and companies must ensure that labeling and format acceptance align, not just resin type.

Closing Thoughts: Aligning Performance, Policy, and End-of-Life Reality

The conversation around PET liners, EPS, and now Biodegradable EPS highlights a fundamental truth: packaging choices must be guided by real infrastructure, regulatory clarity, and proven performance – not just marketing claims. PET liners may use recyclable resins, but their format is not accepted in curbside systems, and chasing arrows alone won’t change that.

EPS remains a high-performing workhorse for cold chain logistics, offering structure and thermal assurance that flexible liners cannot match. EPS is recyclable through 600+ drop-off sites across the U.S. Can be densified and turned into useful products like frames and construction moldings.

Biodegradable EPS builds on this foundation, delivering the same insulation and recyclability benefits as EPS through the national drop-off network, while introducing an enhanced biodegradation pathway in active landfills. As regulations like the FTC Green Guides and California SB 343 sharpen the definition of “recyclable,” choosing materials that align performance with truthful claims and practical end-of-life solutions is becoming a strategic imperative. In short, resin isn’t enough – format, policy, and infrastructure matter.

Stay Informed. Choose Responsibly.

Navigating the intersection of performance, policy, and sustainability isn’t simple – but imperative to the protection of high value shipments and your company’s compliance. ThermoSafe partners with companies to design packaging solutions that perform reliably, comply with evolving regulations, and align with real recycling infrastructure, not just marketing trends.

Explore ThermoSafe’s sustainable temperature assurance solutions and subscribe to the Cold Chain Exchange blog for insights on packaging legislation, materials innovation, and sustainability best practices shaping the future of cold chain logistics.