Lidding Film Compatibility Chart for CPET, APET, PET/PE and PP Trays

Lidding Film Compatibility Matrix for CPET, APET, PET/PE and PP Trays

The correct lidding film is selected by matching its heat-seal layer to the material exposed on the tray flange—not simply to the material named on the tray specification.

This distinction is especially important when sourcing lidding film for PET tray applications. An APET tray normally presents a PET sealing surface, while a PET/PE tray may present PE at the flange. Although both trays contain PET, they usually require different lidding-film sealants.

The following chart provides practical starting points for film selection and line trials.

* These temperatures are screening ranges, not guaranteed production settings. Low-seal-initiation and universal films may operate outside these ranges. Always begin with the film supplier’s technical data sheet and verify the window on the actual machine.

† Service temperature describes storage or reheating conditions. It is not the same as the sealing-jaw temperature. Every oven, microwave, freezer or retort claim must apply to the complete tray–film–food system.

Why the Tray’s Flange Surface Determines Compatibility

A lidding film normally contains several functional layers:

• An outer PET or BOPET layer for strength, clarity, dimensional stability and printing

• An optional EVOH, coating or other barrier layer

• A laminating adhesive or tie layer

• An inside heat-seal layer that makes direct contact with the tray flange

• Optional anti-fog, peel or venting functionality

Only the innermost heat-seal layer forms the bond to the tray. Its chemistry must be compatible with the polymer or coating exposed on the flange.

This is why a film described only as “PET lidding film” is not automatically suitable for every PET-containing tray. The outer carrier might be PET, while the sealant could be PE, PP or a proprietary universal coating.

Before ordering, confirm:

1. The tray’s complete structure, not just its general material name

2. Which layer is exposed on the sealing flange

3. Whether the flange has a coating, seal skin or recycled-content formulation

4. Whether the required closure is easy peel, heat release or lock seal

5. The storage, distribution and reheating cycle of the complete package

What Is the Best Film for a CPET Tray?

A film for CPET tray applications should normally use a dimensionally stable PET or BOPET carrier with a CPET-compatible heat-seal coating. If the package will enter a conventional oven with the lid attached, every component must be qualified for the specified oven temperature and time.

That qualification includes the film, heat-seal coating, laminate adhesive, inks, anti-fog treatment, tray flange and printed consumer instructions.

Choose the CPET peel behavior by application

• Cold easy peel: The consumer removes the lid before heating. The seal must remain secure through chilled or frozen distribution but open cleanly at preparation.

• Heat-release peel: The film remains sealed during storage and releases or vents in a controlled manner as the meal is heated.

• Peel-back or vented heating: The consumer partially peels, pierces or opens a designed vent before microwave or oven heating.

• Lock seal: A permanent closure is used where maximum security is required and the lid is opened by cutting or tearing.

CPET trays may have different surface formulations or an amorphous PET seal skin. Therefore, two trays both sold as CPET can produce different seal strengths with the same film.

Do not infer ovenability from the PET outer layer

A generic PET/PE laminate is not automatically ovenable. Although the PET carrier may tolerate elevated temperatures, the PE sealant, adhesive, printing ink and anti-fog treatment may have lower limits.

Use only a film grade validated for:

• The exact CPET tray

• Maximum oven temperature

• Heating duration

• Food type and fill weight

• Whether the lid remains fully attached

• Required venting or peel-back instructions

How to Select Lidding Film for APET and rPET Trays

APET is commonly used for chilled foods, produce, bakery products, salads, dairy items and fresh proteins. It offers excellent clarity but is not normally selected for conventional-oven heating.

For a plain APET flange, the preferred options are generally:

• Heat-seal-coated BOPET

• Mono-PET lidding film with a PET-compatible seal coating

• High-barrier PET laminate with a PET-compatible sealant

• Universal easy-peel film specifically tested against APET

A good APET lidding film should develop enough seal strength for handling and distribution without requiring excessive heat that distorts the flange.

Recycled content, pigments, anti-block additives and tray-manufacturing conditions can alter the sealing window. An rPET tray should therefore be qualified as an actual tray grade rather than assumed to behave exactly like virgin APET.

For chilled products, consider combining PET compatibility with:

• Cold anti-fog performance

• High clarity

• Controlled easy peel

• MAP barrier

• Laser or mechanical perforation

• Reverse printing

• Low-temperature impact resistance

Why PET/PE Trays Usually Need a PE-Seal Lidding Film

PET/PE trays are multilayer structures. PET contributes stiffness and appearance, while PE may provide sealing performance and moisture resistance. If PE is exposed on the flange, the lid must seal to PE—even though the tray is commonly marketed as a PET tray.

Typical choices include:

• BOPET/PE for general chilled applications

• PET/EVOH/PE for higher oxygen-barrier requirements

• Printed PET laminated to a peelable PE sealant

• PE-compatible universal lidding film

This is one of the most frequent causes of purchasing errors. A PET-compatible coating intended for plain APET may not bond reliably to a PE sealing surface. Conversely, a PE-seal film should not be assumed to seal directly to every uncoated CPET or APET flange.

When requesting lidding film for PET tray packaging, always state whether the tray is:

• Mono APET or rPET

• CPET

• PET/PE

• PET/EVOH/PE

• PET with a proprietary sealing skin

Which Lidding Film Works with PP Trays?

PP trays normally require a PP-compatible sealant such as CPP, a modified PP blend or a proprietary universal coating validated against PP.

Common structures include:

• BOPET/CPP

• PET/PP

• PET/EVOH/PP

• BOPP or coextruded PP-based lidding film

• Universal peelable film qualified for PP

PP is widely used for chilled meals, deli foods, microwaveable products and hot-fill applications. However, standard microwave suitability does not mean that the package is retortable or conventional-oven safe.

A retort package requires a film, sealant, adhesive and printing system designed to withstand the complete pressure-and-temperature cycle. Seal strength should be evaluated both before and after processing.

Easy Peel, Heat-Release and Lock Seal Explained

The term “peelable” describes the consumer experience, but different seal mechanisms can create that experience.

Unplanned laminate delamination is not an acceptable easy-peel mechanism. If the outer film separates from its sealant, the package may leave material on the flange, expose ink or adhesive, and produce an inconsistent consumer experience.

Sealing Temperature Is Not the Same as Oven Temperature

A sealing-jaw setpoint may be 180°C, but the sealing interface is exposed for only a fraction of a second and may never reach the full jaw temperature. An oven cycle exposes the entire package to heat for several minutes.

These are separate specifications:

• Seal initiation temperature: The point at which a measurable bond begins to form.

• Operating window: The combination of temperature, dwell time and pressure that produces acceptable seals.

• Hot tack: The ability of the fresh seal to resist opening before it cools.

• Service temperature: The temperature encountered during filling, storage, reheating or cooking.

• Maximum thermal cycle: The qualified temperature and duration for the complete package.

Film thickness, tool coatings, line speed, tray temperature and heat transfer through the web all influence the relationship between jaw temperature and interface temperature.

For this reason, copying a temperature setting from another production line is unreliable—even when both lines use nominally similar trays and films.

How to Establish a Reliable Sealing Window

A production setting should be based on a controlled line trial rather than a single successful package.

1. Confirm the material interface

Obtain the tray structure and identify the polymer or coating exposed on the flange. If documentation is incomplete, send physical trays to the film converter for compatibility testing.

2. Use the supplier’s recommended starting conditions

Record:

• Jaw or platen temperature

• Dwell time

• Sealing pressure

• Seal width

• Tool and tray temperature

• Line speed

• Film orientation

• Product filling temperature

3. Test several parameter combinations

Create low, middle and high settings around the recommended range. Change one variable at a time or use a documented design of experiments.

The objective is to find a stable operating window—not merely the highest possible peel force.

4. Evaluate strength and integrity separately

Seal strength and leak resistance are related but are not the same measurement. A strong seal can still contain a channel, while a clean hermetic seal does not always require maximum opening force.

Useful qualification methods include:

• Seal-strength testing based on ASTM F88/F88M

• Laboratory heat-seal evaluation based on ASTM F2029

• Visual seal inspection

• Dye penetration suitable for nonporous packaging

• Bubble, vacuum or pressure-based leak testing

• Burst or creep testing where appropriate

• MAP headspace and gas-retention testing

• Distribution, vibration and drop testing

5. Repeat testing after the real thermal cycle

Evaluate the pack after its actual conditions, including:

• Hot filling

• Chilled storage

• Freezing and thawing

• Microwave reheating

• Conventional-oven cooking

• Retort processing

• Intended shelf-life period

Peel force, brittleness, leakage and delamination may change after conditioning.

Barrier, Anti-Fog and Other Performance Options

Tray compatibility is the first requirement, but it is not the only one.

Oxygen and moisture barrier

For MAP and shelf-life-sensitive foods, specify measurable oxygen transmission rate and water-vapor transmission rate requirements. Record the temperature and humidity at which each value is measured.

EVOH can provide high oxygen barrier, but its performance depends on structure and environmental conditions. Shelf life should be validated using the complete package and food product.

Anti-fog performance

Anti-fog treatment helps condensed moisture spread into a transparent layer rather than forming visible droplets. Specify:

• Hot or cold anti-fog

• Food and filling temperature

• Storage temperature

• Test duration

• Film side carrying the treatment

• Acceptable visual result

Anti-fog should not be allowed to reduce seal strength or contaminate the flange.

Printing and coding

Reverse printing places the artwork inside the laminate, helping protect it from abrasion. Inks and adhesives must be suitable for the intended food-contact construction and thermal cycle.

Confirm roll direction, eye-mark position, repeat length, transparent windows and date-code areas before production.

Venting and permeability

Microwave meals may require a laser-scored vent, valve or controlled heat-release seal. Fresh produce may need macro- or microperforation rather than maximum barrier.

“High barrier” is not automatically better. The correct gas transmission rate depends on the food’s respiration, shelf-life target and packaging atmosphere.

Common Lidding Film Problems and Corrective Actions

Information to Provide When Requesting a Lidding Film Quote

A complete specification reduces sampling time and prevents incompatible film from reaching a production trial.

Provide the following information:

1. Tray manufacturer and product code

2. Complete tray structure and actual flange contact layer

3. Tray drawing, flange width and number of compartments

4. Tray-sealing machine brand and model

5. Required film width, thickness, core size and maximum roll diameter

6. Winding direction and printed repeat length

7. Easy peel, heat-release, resealable or lock-seal requirement

8. Target peel-force range, if available

9. Food type, fat, moisture, sauce and likely flange contamination

10. Filling temperature and line speed

11. Chilled, frozen, MAP, microwave, oven or retort conditions

12. Required OTR, WVTR, anti-fog, perforation and printing performance

13. Applicable food-contact and market regulations

14. Expected annual volume and trial-roll requirement

A useful request format is:

We need a [width and thickness] lidding film for [tray code and structure]. The exposed flange layer is [PET, PE or PP]. The package requires [peel type], [storage conditions], [heating process], [barrier level] and [printing requirements] on a [machine model] tray sealer.

Frequently Asked Questions

What is the best lidding film for a PET tray?

First determine whether the flange presents PET or PE. Plain APET generally needs a PET-compatible coating, while PET/PE trays with PE on the flange normally need a PE-compatible sealant.

Can one lidding film seal to CPET, APET and PP trays?

Yes, some universal sealants are designed for multiple tray surfaces. However, compatibility, peel force and leak resistance must be validated separately on every tray grade and production line.

Which film is suitable for a CPET tray?

The usual starting point is an ovenable BOPET or PET film with a CPET/PET-compatible heat-seal coating. If the lid remains attached during heating, use a film qualified for the exact temperature, time and venting method.

Can PET/PE lidding film seal directly to CPET?

Not automatically. A PE sealing layer may not bond reliably to an uncoated CPET flange unless it is a universal or specially modified grade tested for that surface.

What temperature should be used to seal CPET trays?

Many CPET systems are initially evaluated in the 180–220°C jaw-setpoint range, but the correct setting depends on the film coating, dwell time, pressure, tool and tray surface. The supplier’s technical data must take priority.

Is every CPET lidding film oven safe?

No. CPET tray compatibility and ovenability are different requirements. The complete film structure, adhesive, ink, coating and sealed package must be qualified for the intended oven cycle.

What is the difference between APET and CPET?

APET has an amorphous structure that provides high clarity and is mainly used for chilled packaging. CPET is crystallized for greater heat resistance and is commonly used for ovenable ready meals.

Can an easy-peel seal still be hermetic?

Yes. A properly designed easy-peel system can provide hermetic package integrity while opening at a controlled force. Seal integrity and opening force should be tested separately.

Does a high-barrier film guarantee the required shelf life?

No. Shelf life depends on the lidding film, tray, seal area, food, headspace gas, storage conditions and package integrity. Barrier values alone cannot guarantee product life.

Is mono-PET lidding film recyclable with a PET tray?

A mono-PET combination may improve material compatibility, but recyclability still depends on coatings, inks, adhesives, labels, food residue and the collection and recycling infrastructure in the target market.

Final Selection Rule

For reliable tray sealing, use this order of decisions:

Identify the exposed flange material → match the lidding seal layer → choose peel behavior → define barrier and thermal requirements → establish the sealing window → validate the complete package.

Never approve a film solely because its product description lists CPET, APET, PET/PE or PP. Request technical data, test the actual tray and run production-speed trials before placing a full-volume order.

To obtain an accurate recommendation, send your tray specification or physical samples together with the machine model, food type, heating process and required peel behavior.