EPP - Expanded Polypropylene

What is EPP

Expanded Polypropylene (EPP) is a highly versatile closed-cell bead foam consisting in 95% air, which gives it extraordinary lightness and a high strength to weight ratio. Combined with other components, it is successfully used in technical parts as it joins strength and lightness and thus optimizes manufacturing costs.

This, along with a great mechanical resistance and other unique characteristics such as acoustical absorption, thermal insulation, buoyancy, water and chemical resistance and 100% recyclability makes it a trustworthy material used in a wide variety of industrial applications.

How to process EPP

The processing of EPP is complex, requiring both technical expertise and specialized equipment. Basically, it consists of 4 steps:

1 - Expanded

The expanded polypropylene pellets (EPP) arrive at the factory in trucks from where they are sucked into the storage silos.

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2 - Moulding

The EPP beads are sucked from the silo to the pressure filling device of the moulding machine.

3 - duly pressurised

The beads, duly pressurised, are introduced into the mould through pressurised air ducts.

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4 - the beads are welded together

Once in the mould, the beads are welded together thanks to the water vapour that is introduced into the mould. Depending on the shape and density, the pressure can vary between 2.5 and 3.5 bars.

5 - Reduced

After welding, the pressure of the moulded part must be reduced so that it can be removed from the mould. For this purpose, water is introduced through the cooling system of the injector.

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6 - Stabilised

Sometimes, some parts have to be stabilised in hot air ovens to recover the desired shape.

Properties of EPP

As stated previously, EPP has some outstanding properties that make it a really appreciated material:


Being 95% air, EPP is much lighter than other materials. This characteristic implies lots of benefits, such as an improvement of the structures where it is used, a drastic reduction in transportation costs and an easier recycling process. If we add that it has an exceptionally high strength-to-weight ratio there is no doubt that it can be certainly useful in a variety of applications such as construction or logistics.

Thermal and sound insulation:

These properties are specially appreciated in construction and HVAC systems. On the one hand, effective thermal insulation guarantees that spaces stay at the right temperature, reducing energy losses. For its part, sound insulation prevents the acoustic nuisances that HVAC systems can cause or that can be found outside a building.

Shock absorption:

Energy absorption during impact makes EPP a suitable material to ensure shock protection in cases where it is fundamental, such as the logistics of fragile products, electronic devices or automotive components.

100% recyclability:

EPP is a sustainable material, as it is completely recyclable, meaning that it can be recovered and reused several times. Furthermore, being a mono material facilitates its recycling process. This is a great contribution to a circular economy and helps reduce the carbon footprint.

Apart from these already useful qualities, it can also be supplemented with some additives to give it various electrostatic and fire resistance characteristics, which surely make it even more versatile.

History of EPP


Discovered at the beginning


Karl Ziegler managed to make it high-density


began to be commercialized in Europe


production and commercialization


Polypropylene (PP) was discovered at the beginning of the 50’s while various research groups around the world were working on the polymerization of olefins. Several of them managed to synthesize solid PP in the laboratory, although it was not suitable for industrial use.

It was not until 1953 when Karl Ziegler managed to make it high-density thanks to organometallic catalysts that would eventually be called Ziegler catalysts. One year later, Giulio Natta, following the work carried out by Ziegler, managed to obtain isotactic polypropylene, this means with a very regular structure. As a curiosity, it must be stated that all this work was so relevant that both researchers shared a Nobel Prize in Chemistry.

In 1957, PP began to be commercialized in Europe and North America. However, despite being semi-crystalline and affordable, surpassing polyethylene in mechanical properties and having the lowest density, it was highly sensitive to cold and ultraviolet light. This is why it was reduced to few applications, basically domestic utensils.

Later on, with the discovery of new light stabilizers and the greater resistance to cold achieved with propylene, these inconveniences were solved and it began to have increasingly new applications, especially for automotive products. From 1983, due to several mergers between the main producers, the production and commercialization of PP significantly increased until nowadays.

EPP Applications

EPP is highly versatile and has lots of applications, particularly standing out the following ones:




home appliances


Automotive industry

The mechanical resistance and high impact absorption of EPP make it the perfect material for certain passive safety elements in vehicles, as it provides ergonomics and protects passengers against injuries in the event of an accident. This is why it is used in seats, boot compartments, or mat cushions, among others Conversely, its lightweight enables to reduce fuel consumption and achieve greater energy efficiency.


The most appreciated characteristics here are isothermality, breathability and protection to shocks and vibrations as it enables creating appropriate packaging that helps fight food waste. Also UV resistance and non-toxicity are key properties. Thanks to EPP food is well preserved and is properly protected during transport without the need for refrigeration.


Heating, Ventilation and Air Conditioning is another field where EPP material perfectly fits. Due to its lightweight nature it is a step forward compared to previously heavier structures. For its part, thermal insulation guarantees a reduction in energy losses throughout the system and impermeability prevents condensation and its direct consequence: mould growth. Fire resistance and soundproofing are also highlighted advantages of this material, especially for those HVAC systems installed in industrial environments. For all these reasons, it is frequently used in boiler components, radiators, hot water tanks or air-conditioning units, among others.


thanks to its high resistance to impact, compression and temperature and low water absorption capacity, EPP material is perfectly suitable to protect delicate electronic components which must stay away from water or sudden temperature changes. It is also a great alternative to substitute wires, clips and metal boards that only serve to hold components in place.

Our EPP Products

At Knauf Industries we endeavor to offer you eco-designed solutions, incorporating all the stages of the product life cycle. Some of our most highlighted EPP products are the following:

Ventilation cases

Ventilation is a very important element of HVAC installation, as it ensures proper air circulation. At Knauf Industries we developed various light-weight insulating solutions in cooperation with many renowned ventilation equipment producers. We deliver EPP housings for ventilation units to insulate the equipment while keeping the aesthetics of the space.

The EPP material is an ideal choice due to its ability to fulfill the defined air-tightness requirements. It is important to state that, even if some norms define a certain level of air-tightness, in Knauf Industries Appliances we want to offer added value to our partners and have set an ambitious goal to limit it to 2%.

Insulation of hot water tanks

It is not easy to get a nice finish around hydraulic connections, as the foaming pressure can easily outstrip junctures. However, thanks to EPP material the foam can mould all the shape to ensure perfect subjection avoiding any leak during the process.


Protective packaging and logistic solutions

Knauf Industries is an international expert in the design and manufacture of protective packaging and technical parts. Our packaging solutions are intended for many business sectors, such as industrial manufacturers, SMEs-SMIs, distributors and retailers.  

EPP closed-cell structure provides reliable protection against shocks and compression, ideal for maintaining the integrity of products throughout its logistic cycle. Furthermore, we also develop isothermal solutions for heat-sensitive items. This way we guarantee compliance with fundamental supply chain requirements: safety, protection and logistics.

In this regard, we also provide complete solutions for the agri-food industry. One example of it is our Komebac® box, which is reusable and customizable and has become a great ally of last-mile transport, especially under high temperatures.


Car seats for children

One of the most important challenges for the automotive industry is to balance the high strength of the components with the need to reduce vehicle weight and maintain safety at the same time.

Jointly with Karwala company we have successfully designed and launched an innovative, ultra-light and durable child safety seat made with EPP material. It is distinguished for being 40% lower weight than products available on the market until now and improving the safety due to the great impact absorption of this material.

We also have at your disposal around 40 different models of surface finishes for EPP, which allows us to offer a great customization experience. In addition, we can design ad-hoc finishes.

Our catalogue of finishes offers a complete range of very high quality textures.

It consists of four graphic themes inspired by current trends, each theme, in turn,

is made up of nine specific finishes.

One of the missions of our technical team, in addition to giving you support in the shape and thicknesses to your needs, is to guide you in the customisation of your product to provide you with greater added value.

Improving the visual aspect, reducing elements and optimising the carbon footprint of your product.

During the design process, we preview the figures with realistic renders of each piece. This way we help you choose the desired texture.


  • A very subtle, fine-grained surface.
  • fine-grained surface.


  • Inspired by mineral
  • finish with a contrasting
  • Texture.


  • Finishes that evoke
  • fabrics and natural
  • and natural fibres.


  • Texture of plant forms
  • vegetal shapes with refined
  • refined details.

Colour range

There are currently 6 colours available: Cranberry, Blue, Pink, Orange, Yellow, Green, White and Black. Blue, Pink, Orange, Yellow, Green, White and Black.

Not all colours are available for all grades. Please consult your technician for advice and choice.


Our colours have a bulk density of 33g/l, suitable for many types of applications and suitable for food contact.

The weight of each particle is 1.20mg, and the particle size varies between 2.5 and 4.5mm. The recommended moulding density range recommended for coloured EPP ranges from 35 to 65g/l.

"Reducing the weight on our planet"

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