What is the difference between cross-linked IXPE foams (Isolon 300/500) and non-crosslinked PE foams (Warmlex)?

Short answer: Cross-linked IXPE foams such as Isolon 300/500 offer higher dimensional stability, finer cell structure and better mechanical and thermal performance, while non-crosslinked PE foams like Warmlex are more economical and suitable for standard cushioning, underlays and packaging.

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EU buyers often work with both cross-linked and non-crosslinked polyethylene foams and need to decide which material type fits a specific project. This article explains the practical differences between Isolon 300/500 (IXPE) and Warmlex (non-crosslinked PE foam) in terms of structure, performance and typical applications.

Structure and performance: IXPE vs non-crosslinked PE foam

Although both material families are based on polyethylene, their internal structure and performance are different:

• Cross-linked IXPE (Isolon 300/500) – chemically or physically cross-linked polyethylene foam with a fine and uniform cell structure, typical density range from approx. 25 to 200 kg/m³.
• Non-crosslinked PE foam (Warmlex) – physically foamed polyethylene without cross-linking, with a more open cell structure and typical density range from approx. 18 to 45 kg/m³.

Key practical differences for EU projects:

• Dimensional stability – IXPE foams keep their thickness and shape better under long-term compression and temperature changes; non-crosslinked foams are more sensitive to creep and permanent deformation.
• Surface and finish – cross-linked foams usually have a smoother, more homogeneous surface with a “closed skin”; non-crosslinked foams may show a more pronounced cell structure.
• Mechanical properties – IXPE foams provide higher tear resistance, better recovery after compression and improved impact absorption at lower thicknesses.
• Thermal and acoustic performance – both materials provide insulation, but cross-linked foams are often chosen where more stable performance over time is required.
• Cost efficiency – non-crosslinked foams like Warmlex are generally more economical per square metre for standard cushioning and underlay tasks.

Typical applications for Isolon 300/500 and Warmlex

Both foam types are widely used in European markets, but in slightly different roles. Typical areas include:

• Isolon 300/500 (IXPE)
  – technical insulation in construction and HVAC systems;
  – underlays for high-quality flooring and laminate where stable thickness and acoustic comfort are important;
  – gaskets, sealing elements and technical pads, often combined with self-adhesive Isolontape solutions;
  – applications where the material is visible and surface appearance matters.
• Warmlex (non-crosslinked PE foam)
  – standard floor underlays and cushioning layers;
  – protective packaging and liners for boxes and crates;
  – basic vibration damping and gap filling where fine tolerances are not critical;
  – temporary protection during transport and installation.

— define whether long-term dimensional stability or cost per square metre is more critical for your project;
— decide which density range you need and whether repeated compression is expected;
— check if the foam will be visible (surface quality and colour may become important);
— ask LIRIDA-M to recommend a suitable Isolon or Warmlex grade based on your technical and budget requirements.

Frequently asked questions

• Can we replace IXPE with non-crosslinked PE foam to reduce costs? In some cushioning and underlay applications this is possible, but you should always test the alternative foam in your process. For demanding technical applications, IXPE is often required to maintain performance over time.
• Can you propose a foam grade based on our sample or specification? Yes. If you share your target thickness, density, application and any existing reference material, we can suggest suitable Isolon or Warmlex options for lab tests or pilot production.