What is the difference between prime, second-grade and recycled PE foam, and what does LIRIDA-M supply by default?

Short answer: By default LIRIDA-M supplies prime-grade PE foams and self-adhesive tapes based on NPE, XPE/CPE, IXPE and EVA. Second-grade or recycled foam can be used for specific projects, but this is always discussed in advance and clearly marked in offers and documentation.

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European buyers often ask whether technical foams are prime-grade or contain recycled content. This article explains the difference between prime, second-grade and recycled PE foam materials and clarifies what you can expect from LIRIDA-M when ordering Warmlex (NPE), Isolon 300/500 (XPE/CPE, IXPE), Isolontape and EVA-based foams.

Prime, second-grade and recycled PE foams: what is the difference?

In practice, foam materials on the market can be grouped into three broad categories:

• Prime-grade foam – produced from virgin raw materials according to the manufacturer’s specification, with stable structure, colour and mechanical properties. This is the default option for most technical and construction applications.
• Second-grade foam – material that formally meets the basic type specification but has visible defects (colour streaks, surface marks, small inclusions, uneven cell structure) or deviations outside normal tolerances. Often sold at a discount for less demanding uses.
• Recycled or regrind-based foam – foam that uses a significant share of recycled PE or process regrind. Performance and appearance can vary strongly from batch to batch.

For our main product families this can be summarised as follows:

• NPE / non-crosslinked PE foam (Warmlex) – standard underlay and cushioning foam, usually supplied as prime-grade; economy grades with lower visual requirements are possible by agreement.
• XPE / CPE (chemically cross-linked) – Isolon 300 – technical foam with a defined cell structure and surface; projects normally require prime-grade material.
• IXPE (irradiation cross-linked) – Isolon 500 – high-value technical foam where stable structure and properties are critical; typically supplied as prime-grade only.
• XPE/IXPE-based self-adhesive tapes – Isolontape and similar – foam + adhesive system where both foam quality and bonding are important.
• EVA / PE+EVA foams – used where elasticity and resilience are important; quality of the copolymer mix has a strong impact on performance.

How can buyers recognise low-grade or recycled foam in practice?

In real life, buyers and quality teams usually do not analyse the exact recycling content, but they can recognise lower-grade foam by visual and physical signs.

• Visual appearance – irregular or coarse cell structure, large pores, visible inclusions, streaks or stains in the foam body.
• Colour consistency – strong colour variation within one batch or even within one roll or sheet; “dirty” or greyish shade in materials expected to be white or light-coloured.
• Surface quality – rough or “crumbly” surface, dust formation when handling or cutting, poorly formed skin layers.
• Compression behaviour – poor recovery after compression, permanent deformation even under moderate loads, noticeable creep in underlay applications.
• Odour – strong or unusual chemical odours during unpacking or storage may indicate non-standard raw materials or poor process control.

These indicators do not automatically mean that the foam is unusable, but they often signal that it belongs to a lower-grade category and may not be suitable for demanding technical applications.

— check visual appearance, cell structure and surface quality on several samples from each delivery;
— compare the feel and recovery behaviour with previous prime-grade batches you have used;
— ask LIRIDA-M to confirm whether the offered material is prime-grade or a special downgraded/recycled option;
— use downgraded or recycled foams only in applications where variable appearance and properties are acceptable.

Frequently asked questions

• Do you use recycled PE in your standard Isolon, Warmlex or Isolontape materials? Our standard offer for technical projects is based on prime-grade foam. If recycled content is relevant for a specific project, this must be discussed separately and clearly reflected in the documentation.
• Can you supply second-grade foam for non-critical packaging? In some cases we can discuss downgraded or off-spec material for non-visible or non-critical packaging tasks. Such options are always marked separately, with clear indication of possible visual and performance limitations.