Foam – the all-rounder

Foam – the all-rounder

Foam is unassuming. It has become an indispensable part of our daily lives, yet it remains unobtrusive and understated. But what is foam actually made of, and how is it produced? What are its outstanding properties, and where can it be used?

This blog post provides answers to everyday and not-so-everyday questions about this all-rounder.

How is foam made?

The properties of different types of foam can vary greatly. 

In physical foaming, the raw material is caused to foam through physical action. In chemical foaming, a blowing agent is added to the raw material, causing it to foam. In mechanical foaming, air is stirred into the raw material, causing the resin or paste to foam.

PU foam end product: 

Polyurethane foam, PUR, PE, PU foam

PU foam and PE foam are the most commonly used materials. These foams are produced using the PU process or the PUR process. In this process, two reactive starting materials, namely polyol and isocyanate, are mixed with a blowing agent. The starting materials then react to form polyurethane foam. This results in gas entrapment. Depending on the formulation, the properties of the PUR foam can vary, resulting in soft, elastic or harder, less elastic foams.

Continuous production 

In the continuous production of PUR foam, the main raw materials, polyol and isocyanate, are fed via separate lines into a mixing chamber using a pump system and mixed homogeneously. The mixture is applied to a paper web and then reacts to form PU foam. Once the reaction is complete, the material can be further processed.

Moulded foam production

In moulded foam production, a mixture of the main raw materials – polyol, isocyanate and other secondary components – is poured into a mould in liquid form. This mixture expands and thus completely fills the mould. The moulded parts can then be further processed. In addition to the production of PU foam, there are a number of other types of foam and production methods.

How is foam made?

The properties of different types of foam can vary greatly. 

In physical foaming, the raw material is caused to foam through physical action. In chemical foaming, a blowing agent is added to the raw material, causing it to foam. In mechanical foaming, air is stirred into the raw material, causing the resin or paste to foam.

PU foams End product:

Polyurethane foam, PUR, PE, PU foam

PU foam and PE foam are the most commonly used materials. These foams are produced using the PU process or the PUR process. In this process, two reactive starting materials, namely polyol and isocyanate, are mixed with a blowing agent. The starting materials then react to form polyurethane foam. This results in gas entrapment. Depending on the formulation, the properties of the PUR foam can vary, resulting in soft, elastic or harder, less elastic foams.

Continuous production

In the continuous production of PUR foam, the main raw materials, polyol and isocyanate, are fed via separate lines into a mixing chamber using a pump system and mixed homogeneously. The mixture is applied to a paper web and then reacts to form PU foam. Once the reaction is complete, the material can be further processed.

Moulded foam production

In moulded foam production, a mixture of the main raw materials – polyol, isocyanate and other secondary components – is poured into a mould in liquid form. This mixture expands and thus completely fills the mould. The moulded parts can then be further processed. In addition to the production of PU foam, there are a number of other types of foam and production methods.

What types of foam are there?

Foams are divided into four different categories. These differ in their properties and, consequently, in their areas of application.

Open-cell foams 

In this type of foam, the cell walls are open. This enables these foams to absorb liquids, as is necessary for sponges, for example. It is precisely this type of foam that is also used to absorb sound. When used in seating or reclining furniture, these foams offer excellent ventilation properties. 

Closed-cell foams  

In this type, the cells are closed and therefore cannot absorb liquids or sound waves. Closed-cell foams are frequently used for sealing, insulating, damping and protection in the packaging sector. Well-known branded products in this category include, for example, Ethafoam® PE packaging foams Plastazote® PE packaging foams. Key properties of these materials include good resistance to ageing and excellent thermal insulation. Furthermore, these foams are weather-resistant and resistant to chemicals. PE foams are closed-cell foams, which can in turn be divided into cross-linked and non-cross-linked foams. In cross-linked PE foams, the polymer chains are linked together at specific points. Cross-linked foams have a regular, closed structure. This means that these foams do not absorb air or liquid. Furthermore, they are only slightly elastic and are water-repellent or waterproof. In non-cross-linked PE foams, the polymer chains are not linked together. All non-cross-linked PE foams can be granulated and recycled. In applications requiring large volumes, such as in the packaging industry, the advantages of this cost-effective material come into their own.

Mixed-cell foams 

Mixed-cell foams, as the name suggests, are a blend of open-cell and closed-cell foams.

Integral foams 

These foams also have open and closed cells. The distinctive feature of integral foams is that the outer skin consists of closed cells, whilst the core consists of open cells. Integral foams are frequently used in automotive manufacturing, for example for armrests, headrests or, on the exterior, for front or rear spoilers. Wherever high safety requirements (in terms of shock absorption) and sound insulation are required, integral foams are the first choice.

Interpretation of compression hardness and density

The interpretation of compression hardness and density in foams is crucial to understanding the strength, elasticity and comfort of materials such as mattresses and upholstered furniture.

What is the compression hardness of foams? 

Compression hardness, or foam hardness, is a measure used to indicate the firmness or hardness of a foam. It is measured in pascals (kPa) and represents the force required to compress the foam to 60% of its original height. The higher this value, the harder the foam. A value of 20 to 30 means that the material is relatively soft; such a material is suitable for upholstering seats and backrests. If the value is above 35, it is a very high-quality material that can be used in almost all applications. 

What is the density of foam? 

Density is the other key quality characteristic of foams. It indicates the weight per cubic metre of the foam (kg/m³). The higher the density, the better the material’s properties, particularly high foam strength with minimal material fatigue.

What does RG 35 50 signify in foam specifications? 

Such specifications are often included in mattress descriptions. RG = density 35 (first set of digits) = density of 35 kg per cubic metre 50 (second set of digits) = compression hardness in pascals or 5 kilopascals (kPa)

PUR foam 

G=Density / Compression hardness RG 20 / 35 soft RG 25 / 45 medium firm RG 35 / 50 firm RG 40 / 60 very firm 
Cold foam G=Density / Compression hardness RG 30 / 25 soft RG 35 / 35 medium firm RG 40 / 45 firm 
Viscoelastic foam G=Density / Compression hardness RG 50 / 15 soft RG 50 / 20 medium firm 
Composite foam G=Density / Compression hardness RG 100 firm RG 120 very firm

Properties of foam

Foams with electrical conductivity, thermal conductivity, sound insulation and various fire resistance ratings are used in a wide range of applications in the electronics, packaging and construction industries.

Conductive foams 

Essentially, foam has low conductivity. This can be changed by adding graphite. Polyurethane foam is immersed in a solution containing graphene oxide for this purpose. Using this process, foam can also be transformed into an extremely conductive material, which is primarily used in the electronics industry. However, the packaging industry also relies on a certain level of conductivity in foams. For example, this is used to protect electrical and electronic devices from static charge.

Thermal conductivity of foams 

Thermal conductivity W / (m K) (watts per metre and Kelvin) or λ indicates the heat flow passing through a 1 m² layer of material 1 m thick when there is a temperature difference of 1 Kelvin (K). The lower λ is, the better the insulating capacity of a foam. In insulation materials, the thermal conductivity of the base material and the bulk density mainly influence the thermal conductivity of the foams. In closed-cell foams PUR and extruded polystyrene foam (XPS), the following factors are important for the thermal conductivity: the nature and quantity of the blowing agent and the length of time the blowing agent remains in the foam cells.

Foam with sound insulation properties 

The ability of a foam to insulate sound is described by the sound absorption coefficient. This is defined as the ratio of the absorbed sound intensity (sound insulation) to the total incident sound intensity. Sound-absorbing acoustic foam or foam for noise insulation is produced using special manufacturing processes. The surfaces of these acoustic panels can be profiled, with different profiles having different effects on the behaviour of the sound. 

Flammability of foams 

Foam is flammable. For this reason, this aspect must be given special attention depending on the application. In some areas, the legislator also stipulates which requirements foams must meet in order to be used safely from a fire protection point of view. Various fire protection classes are used to designate materials that meet increased requirements. Fire protection class B1 designates flame-retardant, i.e. virtually fireproof, foams. These foams may normally be used anywhere. These foams hardly burn at all, or only at high temperatures. Fire protection class B2 refers to flammable materials that are less quick to ignite. Fire protection class B3 is highly flammable. Nevertheless, foams in this class are often used because they are inexpensive and in many places the risk of fire is not acute.

Innovative and sustainable foams

Foams with memory effect, bio-based options and a wide range of applications offer innovative solutions for numerous industries.

Foam with memory effect 

A special polymer gives these foams a unique property, namely “shape memory” or the so-called memory effect. This viscoelastic foam is also known as “Tempur”. As soon as pressure or heat is applied, it adapts to the body resting on it. Viscoelastic foams are softer and more supple than conventional foams. The special characteristics of this material were not discovered by chance. Researchers at NASA came across it whilst searching for a foam to provide optimal relief for astronauts during the launch and acceleration phases. Due to their uniqueness, the properties of the newly discovered polymer quickly found widespread use as a component in mattresses and pillows, but also in healthcare as a positioning aid in orthopaedics.

Organic foam or eco-friendly foams 

Foams are usually based on petroleum-derived materials. Replacing this base with renewable raw materials is a sensible addition to established foams. In fact, there are already various materials that can meet higher sustainability standards. Organic foams are produced from various raw materials. For example, there are those made from nanocellulose, milk protein and clay minerals, tall oil and several others. All organic foams have one thing in common: they are biodegradable or compostable.

Use of foams

There are countless uses for foams. Here you will find a non-exhaustive list of various applications: Soundproofing and insulation: recording studios, vehicle manufacturing, equipment manufacturing, etc. Foam insert (foam inlay), e.g. as case insert for tools, watches, equipment storage and packaging. Foam for upholstering furniture, seats and reclining surfaces. Filter foams for insulation in building construction or interior fittings, e.g. as ceiling panels. Foam as combination packaging or as transport protection in the packaging industry. Foam for mattresses and pillows, anti-slip mats, floor protection mats and foam pads. Foam for camping and foam for crafts.

In which colours is foam available?

In principle, foams can be purchased in all colours of the rainbow. If, contrary to expectations, the desired shade cannot be found, it can also be dyed yourself. You can see how this is done in the section "Dyeing foam yourself". 

Processing or working with foams 

Cutting foam yourself – but how? The best way to cut foam is with a common household appliance, namely an electric knife. Most such appliances have two blades that move against each other. This allows thicker plastics to be cut relatively well. Thinner pieces can possibly also be cut with a sharp pair of scissors. For polystyrene, it is advisable to use an insulation knife or an insulation saw. Polystyrene is best broken. The intended breaking point should first be scored with a heated, sharp knife. It can then be broken along the cut edge with little effort. How the professional shapes foams.

The shaping options for professionals are varied. Depending on the requirement, the following are recommended: 

• Cutting, e.g. with a type of band saw (suitable for straight contours)
• Contour cutting, with the contour cutting machine (suitable for complicated shapes)
• Punching, with punching machine (suitable for series production)
• Water jet cutting, with water jet cutting machine (suitable for highly precise complicated cuts)
• Milling, with the milling machine (suitable for three-dimensional shaping)

Buy foam

There are many sources for purchasing foam. Different retailers often cater to specific target groups. The most significant distinction here is whether the buyers are B2B customers or B2C customers. 

Buying foam as a private individual

Private individuals purchase their foam either from specialist retailers or from DIY and hobby shops. The advantage of these channels is that the foam can usually be bought close to where it will be used and can be collected and used immediately. This is ideal for businesses that do not require a wide selection, or for private individuals, e.g. for craft supplies or similar. In terms of price, these sales channels are in the mid to higher price ranges, as foam is not a product with which retailers seek to distinguish themselves, but rather a product category with which they can achieve good contribution margins. Another option is online shops where foam can be bought cheaply online. Private individuals can often meet their foam requirements here too.

The advantages of this sales channel are that prices are often lower and, more importantly, that almost any material requirement can be met. You often even have the option of having the foam cut to size. Furthermore, the goods are conveniently delivered to your home. When choosing a shop, you should ensure that the supplier is a company with a Swiss branch and a Swiss warehouse. Otherwise, delivery times can easily be long, or you may even incur customs charges on import. Unfortunately, a .ch domain is not in itself a guarantee that the shop actually delivers from Switzerland. Checking the legal notice often provides certainty. At this point, we at vibraplast would like to emphasise that our online foam shop is happy to deliver to private individuals and is unrivalled in terms of selection, terms and availability. For anyone looking to buy foam at a low price, we recommend our outlet section. Of course, there are other suppliers with good offers, but why look further afield when the best is right on your doorstep?

Foam Wholesale 

Foam wholesalers, or foam suppliers, target larger B2B business customers with their range. The advantages of this channel lie in the product range and the advice provided. Furthermore, individual requirements can be accommodated effectively. Last but not least, this channel can offer favourable volume terms and, where required, provide bespoke logistics solutions. We would also like to take this opportunity to highlight our services as a foam wholesaler and supplier. Our product range, logistics, pricing structures and advice are ideally tailored to the needs of discerning business customers. If you have any requirements in this regard, we look forward to your call under Tel. +41 (0)52 368 00 50

Custom-made foam 

There are countless applications for foam. Consequently, customer requirements regarding size and shape are also diverse. As cutting foam without the appropriate machine tools is a difficult undertaking, we – as well as other suppliers – offer customers a “custom-made foam” service. Over the years, vibraplast has developed a range of sophisticated and highly precise custom foam cut-to-size solutions. You can choose from a wide variety of products in every possible shape and size. Click here to go directly to the custom foam online shop.

Conclusion

As you can see, foam is a true all-rounder. Its range of applications is incredibly diverse, and the various materials differ in their properties and characteristics to such an extent that almost any foam requirement can be met. Should you still have any questions following this comprehensive overview, or if you have any specific requirements regarding the foams available, we look forward to hearing from you.

info@vibraplast.ch