Plastazote is a closed-cell, crosslinked polyethylene (XLPE) foam widely used in engineering, medical devices, orthotics and protective packaging.

It is made from low-density polyethylene (LDPE). This material is crosslinked using high-energy radiation and inert nitrogen gas.

This crosslinking gives Plastazote its unique properties: it softens under heat instead of melting and exhibits exceptional chemical purity. 

According to Zotefoams (the inventor), Plastazote sheets are latex-free, non-toxic, hypoallergenic and inherently pure. In essence, Plastazote is a high-performance polyolefin foam whose cells are completely sealed, making each sheet waterproof and chemically inert.

It does not contain blowing solvents or residual volatiles.  Typical densities range from about 15 to 115 kg/m³, covering everything from very soft to relatively firm grades.  Unlike ordinary polyethylene, the nitrogen-crosslinked structure means the foam does not melt or drip in service; heating above ~100 °C simply causes it to soften and, if prolonged, shrink.

Plastazote sheets begin life as extruded LDPE rolls that are then irradiated and nitrogen-infused (left) and can be produced in many colours (right) for branding or layering.

Manufacturing Process (Nitrogen Expansion)

Plastazote foams are made using a special nitrogen expansion process. This process is patented by Zotefoams and creates uniform, closed-cell blocks. The four key manufacturing steps are:

  • Sheet extrusion: LDPE resin (with any desired additives, colourants or flame retardants) is compounded and extruded into continuous sheets or slabs.
  • Crosslinking: The extruded sheet is irradiated with high-energy electrons (or gamma rays), which “bakes” the polymer into a 3D network. This step greatly increases its thermal resistance and toughness.
  • Nitrogen doping: The crosslinked sheet is heated in a high-pressure chamber filled with pure nitrogen. At elevated temperature, the nitrogen gas dissolves into the polymer matrix.
  • Foaming: The nitrogen-loaded sheet is then transferred to normal pressure (ambient) and heated to just above its softening point. As the pressure drops, the dissolved nitrogen expands and forms millions of tiny gas bubbles. This creates a fine, consistent cell structure throughout the foam.

The process uses no chemical blowing agents and no solvents, so the resulting foam is virtually odourless and sterile. 

Because the nitrogen is borrowed from the atmosphere and then reabsorbed into the foam, the process is also environmentally clean.

Costume

Properties and Advantages

Plastazote’s properties combine lightweight, cushioning and chemical stability. It is well known for being “lightweight & durable” with “good shock-absorbing qualities”. The closed-cell structure makes it impervious to water, oil and most chemicals, so it will not degrade with moisture or microbes. 

It also has excellent thermal insulation, low thermal conductivity and a stable hardness over a wide temperature range.

Zotefoams emphasises that Plastazote is inherently pure, latex-free, non-toxic and hypoallergenic – features critical for medical use.  Many grades are biocompatible and comply with ISO or FDA standards for skin contact, and they do not contain any harmful plasticisers or residual monomers.

Rolls of Plastazote and related foams demonstrate the material’s consistency and purity.  Each batch has a uniform cell size and density profile, giving predictable cushioning.

The foam’s buoyancy and flexibility also makes it ideal for padding and impact protection: for example, it is used in sports equipment and helmets for energy absorption.

Because Plastazote has no set memory and very low creep, it retains its shape and thickness under sustained loads better than some cheaper open-cell foams.

PottertonPacs notes that Plastazote is “waterproof and long-lasting”, with “excellent chemical resistance”.  It is also X‑ray, CT and MRI‑transparent, which is extremely useful in medical settings (e.g. imaging patients with orthoses or braces).

In summary, key advantages of Plastazote sheets include:

  • Biocompatibility: inert, non-toxic, hypoallergenic; safe for direct patient contact.
  • Excellent cushioning: high impact resistance and energy absorption relative to weight.
  • Fabrication ease: can be readily cut, routed, glued or thermoformed with standard tools.
  • Thermal performance: softens only at high temperatures (≈100–140 °C) and remains stable in normal climates.
  • Chemical and moisture resistance: sealed cells keep out water, oils and gases, and the foam will not rot or support microbial growth.
  • Customisation: available in many densities, colours and special grades (e.g. flame-retardant or conductive variants) for specific applications.

These advantages explain why Plastazote is widely used wherever cushioning, hygiene and precision are important.  It meets engineers’ need for a consistent engineering foam and medical-device designers’ need for a clean, non‑irritating material.

Plastazote Back Brace

Applications in Orthotics, Prosthetics and Podiatry

Plastazote is ubiquitous in foot care and orthopaedic supports.  Its cushioning and mouldable nature make it the material of choice for custom insoles, braces and liners.  In podiatry, for example, multiple densities of Plastazote foam are laminated or thermoformed into orthotic insoles to treat conditions like flat feet, plantar fasciitis, high arches or diabetic neuropathy.

Clinical guides note that “orthopaedic footwear…depends on the lightweight, pliant, shock-absorbing nature of Plastazote foam.” 

A direct-moulding technique is often used: a sheet is preheated in an oven (around 140 °C) and the patient’s foot is pressed into it to capture the plantar contours. This produces a perfect foot impression that becomes the customised sole. 

Plastazote is also the standard for protective braces and splints. Its softness against skin and lack of odour prevent irritation under the straps.

Producers of medical collars, spinal supports, elbow and knee braces and prosthesis liners frequently line the device with a thin sheet of Plastazote. 

Higher-density grades can be bonded behind for rigidity while still remaining lightweight.

In prosthetics, Plastazote serves as a comfortable interface and cosmetic cover.  Its flexibility and durability make it an ideal padding material inside limb sockets.

The company Zotefoams even markets specific grades (LD45, LD24, etc.) for lower-limb prosthetic liners and foot shells.  The material is easy to trim or thermoform around a prosthetic socket, and because it is odorless and hypoallergenic, it is suitable for prolonged skin contact.

As one summary states, “the ease with which Plastazote foams can be cut to shape or moulded, their low weight, durability and non‑irritant properties makes them a natural prosthetic material".

It is “well established as a lightweight cosmetic cover for upper and lower limb prostheses”.

Plastazote for Packaging

Packaging and Medical Device Protection

Outside the clinic, Plastazote is extensively used in protective packaging, especially for medical devices and high-value equipment.  In transportation cases and trays, custom-cut or molded Plastazote inserts securely cushion instruments, implants and mobile devices.

Trifibre (a case manufacturer) notes that “Plastazote foam is widely used in medical applications, such as transporting implants, surgical instruments, and mobile medical devices.

Specific grades can withstand irradiation or heat sterilisation, making them suitable for healthcare packaging” .  In practice, this means foam trays in surgical instrument kits, and reusable cases for sterilisable tools.

More generally, Plastazote is popular for flight cases and tool cassettes. Its predictable resilience lets designers specify exactly how much shock protection or snugness is needed.

Contrasting colored foams (e.g. black and pink layers) are laminated so that missing tools or components “pop” visually against the backing. Custom CNC-cut cases for electronics or delicate equipment often use Plastazote for its smooth texture and neat finish.

PottertonPacs highlights that Plastazote is “often used to produce inserts for use within protective cases…in the medical & healthcare, engineering and automotive industries.”.

Some specialised packaging uses include: ESD-protective foams (with conductive additive) for electronics, archival-quality packing for artifacts (owing to its chemical stability and lack of off-gassing ), and flame-retardant grades for defence applications.

In short, where high reliability and purity are needed, Plastazote foam is a go-to material for cushioning and insulation in packaging.

Disadvantages and Limitations

Despite its many strengths, Plastazote has some limitations.  As an engineered foam, it is relatively costly compared to commodity foams; its manufacturing process is more complex.

Crosslinked polyethylene foams in general are not easily recycled by standard melting or reprocessing . Because they do not remelt cleanly, disposal often means incineration or mechanical recycling.  The material is petroleum-based (not biodegradable) and must be managed accordingly.

Thermally, Plastazote will soften above about 70 °C and can shrink if held near its softening point (105–115 °C) for extended periods. This means it cannot be autoclaved or hot-water sterilised without distortion.

Direct ultraviolet (sun) exposure can also degrade the foam over time: extended sunlight (or storage wrapped in clear film in sun) causes shrinkage and warping. Users should therefore avoid leaving Plastazote products in strong sunlight or near heat sources.

Static charge buildup is a minor issue when cutting large sheets: like all insulators, Plastazote can hold static electricity and discharges can occur. Conductive or dissipative grades exist to address this if needed.

Finally, some users note a slight chemical odor or “plastic” smell in newly crosslinked foam (like all foams).  In practice this usually dissipates with airing, and does not affect the foam’s inertness.

In summary, the main drawbacks are cost, non-recyclability, and sensitivities to high heat/UV.  These are manageable through design (e.g. using flame-retardant grades, shading from sun, or choosing alternatives for very hot environments).  In most orthopaedic and packaging uses, the advantages far outweigh these limitations.

Custom Plastazote Use

Working with Plastazote Sheets: Technical Tips

The fun section! When fabricating Plastazote components, certain best practices ensure success:

Cutting and Machining

Plastazote sheets can be cut with sharp blades (e.g. craft knives) or machined on saws, routers and waterjets . 

Always use clean, sharp tools to avoid tearing the material.  Coarser tools (bandsaws, CNC routers) often work well; light dust extraction is recommended since fine foam dust can be generated.

Edges can be sanded or filed to smooth them. Remember that the foam may compress slightly under pressure, so use backing or multiple passes for accuracy.

Thermoforming

To shape foam blocks/thick sheets into 3D forms, heat is applied.  Zotefoams recommends heating LDPE foams (Plastazote) in a fan-assisted oven to about 135–140 °C. At this temperature the foam softens uniformly.

For vacuum or pressure forming, plastic molds or wooden forms can be used.

Never exceed the recommended temperature (about 145 °C), or the foam may shrink excessively.

A practical tip (especially in orthotics) is “direct-to-body” moulding: place the patient’s foot on a preheated sheet on a non-stick surface, thermal protecting material/fabric and apply weight. The foam will cool quickly to hold the shape.

Bonding and Laminating

Plastazote will not stick with ordinary adhesives due to its chemical inertness.  Special contact adhesives (e.g. 3M Super 77 spray) or heat welding are often used to laminate sheets or attach to other materials.

Hot-air welding can fuse sheets edge-to-edge. Before gluing, clean the surface with alcohol and roughen it slightly for better adhesion.

Always test the adhesive on scrap foam first. Double-sided PE-compatible tapes are another option for lightweight bonds.

Laminating Plastazote with other materials is a service provided by Algeos for multi-sheet orders. Get in touch to discuss your requirements.

Static and ESD

In workshops, freshly cut Plastazote can build up static charge. This is not harmful to humans but can discharge sparks. If electrostatic safety is a concern, use antistatic-grade foam or maintain moderate humidity.

Grounding the table and yourself (wrist strap) will dissipate charges.  Zotefoams notes that conductive/dissipative grades are available if ESD control is needed.

Storage and Handling

Store foam sheets flat, away from sunlight and heat sources. UV rays can weaken the foam and cause yellowing.  Also avoid storing sheets tightly wrapped in clear plastic where a greenhouse effect can shrink the top layers.

If foam has been refrigerated or cold-stored, let it warm to room temperature before fabrication; a 24 hour acclimation is suggested. This prevents warping due to thermal expansion when heated.

Finally, keep foam clean – it can attract dust due to static – so bag rolls or use covers if dust must be minimised.

By following these considerations, engineers and clinicians can take full advantage of Plastazote’s versatility. Its ease of cutting and forming (coupled with its biological inertness) make it extremely popular in custom device fabrication.

Proper handling ensures that each Plastazote sheet performs as expected in its final medical or packaging application.

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