Foam - the all-rounder

Foam - the all-rounder

Foam is discreet. It is an integral part of our everyday lives and yet it is unobtrusive and understated. But what is foam actually made of and how is foam produced? What are the outstanding properties of foam and where can it be used? This blog post provides information on everyday and less everyday questions about this all-rounder.

How is foam produced?

The properties of the different types of foam can vary greatly.

In physical foaming, the starting material is made to foam by physical action. In chemical foaming, a foaming agent is added to the base material, which leads to foaming. In mechanical foaming, air is stirred into the starting product, 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 or PUR process. Two reactive starting materials, namely polyol and isocyanate, are mixed with a blowing agent. The starting materials react to form polyurethane foam. This results in gas inclusions. Depending on the recipe, the properties of the PUR foam can vary, resulting in soft, elastic or harder, less elastic foams.

Continuous production

In the continuous production of PU foam, the main raw materials polyol and isocyanate are fed into a mixing chamber via separate pipes 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 processed further.

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 a liquid state. This mass expands and fills the mould completely. 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 categorised into four different types. These differ in their properties and therefore also in their areas of application.

Open-cell foams 

The cell walls of this type of foam are open. This means that these foams are able to absorb liquids, as is necessary for sponges, for example. This type of foam 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 often used for sealing, insulating, damping and protecting in the packaging sector. Well-known branded products from this category include Ethafoam® PE packaging foams Plastazote® PE packaging foams. The special properties of these materials include good ageing resistance and excellent thermal insulation. These foams are also weatherproof and resistant to chemicals. PE foams are closed-cell foams, which in turn can be divided into cross-linked and non-cross-linked foams. In cross-linked PE foams, the polymer chains are connected to each other at certain points. Cross-linked foams have a regular, closed structure. This means that these foams do not absorb air or liquid. They are also only slightly elastic and water-repellent or waterproof. The polymer chains of non-cross-linked PE foams are not connected to each other. All non-crosslinked PE foams can be granulated and recycled. In applications that require a large volume, such as in the packaging industry, the advantages of this inexpensive material are fully realised.

Mixed-cell foams

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

Integral foams

These foams also have open and closed cells. The special feature of integral foams is that the outer skin consists of closed cells, while the core consists of open cells. Integral foams are often used in car construction, for example for armrests, headrests or in the exterior for front or rear spoilers. Integral foams are the first choice wherever high safety requirements (in terms of damping) and noise insulation are needed.

Interpretation of compression hardness and density

Interpreting the compression hardness and density of foams is crucial to understanding the firmness, elasticity and comfort of materials such as mattresses and upholstered furniture.

What is the compression hardness of foams?

What is the density of foams?

The density is the other important quality feature for foams. This indicates the weight per cubic metre of foam (kg/m³). The higher the density, the better the properties of the material, in particular high foam firmness with low material fatigue.

What does RG 35 50 mean for foams?

Such information is often given in the description of mattresses. RG = Volume weight 35 (first block of digits) = Volume weight 35 kg per cubic metre 50 (second block of digits) = Compression hardness in Pascal or 5 kilo Pascal (kPa).

PUR foam

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

Properties of foam

Foams with conductivity, thermal conductivity, sound insulation and different fire protection classes are used in a wide range of applications in the electronics, packaging and construction industries.

Foams with conductivity

Foam basically has a low conductivity. This can be changed by adding graphite. Polyurethane foam is immersed in a solution containing graphene oxide. This process can also be used to turn foam into an extremely conductive material, which is primarily used in the electronics industry. However, the packaging industry also relies on foam materials having a certain level of conductivity. For example, electrical and electronic devices are protected from static charge.

Thermal conductivity of foams

The thermal conductivity W / (m K) (watts per metre and Kelvin) or λ indicates the heat flow that passes through a 1 m² and 1 m thick layer of a material at a temperature difference of 1 Kelvin (K). The lower the λ, the better the insulating capacity of a foam material. In the case of insulating materials, the thermal conductivity of the base material and the density are the main factors influencing the thermal conductivity of the foams. The following factors are important for the thermal conductivity of closed-cell foams PUR and extruded polystyrene foam (XPS): the type and quantity of blowing agent used 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 by the ratio of the absorbed sound intensity (sound insulation) to the total sound intensity. Sound-absorbing acoustic foam or foam for noise insulation is produced using special manufacturing processes. The surface of these acoustic panels can be profiled, whereby different profiles have different effects on the behaviour of the sound.

Flammability of foams

Foam is flammable. For this reason, special attention must be paid to this aspect depending on the application. In some areas, the legislator also specifies which requirements foams must fulfil in order to be used safely in terms of fire protection. Different fire protection classes are used to characterise materials that meet more stringent requirements. Fire protection class B1 characterises flame-retardant, i.e. quasi fire-resistant, foams. These foams can normally be used anywhere. These foams hardly burn at all or only at high temperatures. Fire protection class B2 includes flammable materials that start to burn less quickly. Fire protection class B3 is highly flammable. Nevertheless, foams in this class are often used because they are inexpensive and the risk of fire is not acute in many places.

Innovative and sustainable foams

Foams with memory effect, bio-options and diverse applications offer innovative solutions for numerous industries.

Foam with memory effect

A special polymer gives these foams a special property, namely a ‘shape memory’ or the so-called memory effect. This viscoelastic foam is also known as ‘Tempur’. As soon as pressure or heat is applied to it, it adapts to the body that rests on it. Viscoelastic foams are softer and more pliable than conventional foams. The special characteristics of this material were not discovered by chance. NASA researchers came across it when they were looking for a foam for astronauts to provide them with optimum relief during the launch and acceleration phase. The properties of the newly discovered polymer quickly became widespread due to its unique properties as an ingredient for mattresses and pillows, but also in healthcare medicine as a positioning aid in orthopaedics.

Organic foam or ecological foams

Foams are normally based on petroleum-based materials. Replacing this basis with renewable raw materials is a sensible addition to established foams. In fact, there are already various materials that can fulfil increased requirements in terms of sustainability. Bio-foams are made from various raw materials. For example, there are those made from nano-cellulose, milk protein and clay minerals, tall oil and many more. All bio-foams have one thing in common: they are biodegradable or compostable.

Use of foams

There are countless possible uses for foams. Here you will find a non-exhaustive list of different areas of application: Soundproofing and insulation: recording studios, vehicle construction, apparatus engineering, etc. Foam inserts (foam inlay), e.g. as case inserts for tools, watches, equipment storage and packaging. Foam for upholstering furniture, seats and lying surfaces. Filter foams for insulation in building construction or interior fittings, e.g. as ceiling panels. Foam as combined packaging or as transport protection in the packaging industry. Foams for mattresses and cushions, anti-slip mats, floor protection mats and foam pads. Foams for camping and foam for handicrafts.

What colours is foam available in?

In principle, foams can be purchased in all colours of the rainbow. If, contrary to expectations, the desired colour cannot be found, you can also dye it yourself. You can find out how to do this in the section ‘Colouring foam yourself’.

Processing or machining foams

Cutting foam yourself - but how? The best way to cut foam is with an everyday household appliance, namely an electric knife. Most such appliances have two blades that run against each other. This allows thicker plastics to be cut relatively well. Thinner pieces can also be cut with sharp scissors if necessary. The use of an insulation knife or an insulation saw is recommended for polystyrene. Polystyrene is best broken. The predetermined breaking point should first be scored with a heated, sharp knife. It can then be broken at the cut edge with little effort. How the professional shapes foam.

The shaping options for professionals are diverse. Depending on the requirements, we recommend

• 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 high-precision, complicated cuts)
• Milling, with the milling machine (suitable for three-dimensional shaping)

Buy foams

There are many sources of supply for foams. The different resellers often address specific target groups. The most important distinction is whether the buyers are corporate customers or private customers.

Buying foam as a private individual

Private individuals buy their foams either from specialised retailers or from DIY and hobby stores. The advantage of these channels is that they can usually be purchased not far from the place of use and can be picked up and used immediately. This is ideal for businesses that are not dependent on a wide selection or for private individuals, e.g. for craft supplies or similar. In terms of price, these sales channels are in the medium to higher price ranges, as foam is not a product with which retailers want to make a name for themselves, but rather a product category with which good contribution margins can be achieved. Another option is online shops where you can buy foam at favourable prices online. Private individuals can often also cover their foam requirements here.

The advantages of this sales channel are that the prices are often more favourable and, more importantly, that almost any material request can be fulfilled. You often even have the option of having the foam cut to size. What's more, the goods are conveniently delivered to your home. When choosing a shop, you should make sure that the supplier is a company with a Swiss branch and a Swiss warehouse. Otherwise it can quickly happen that delivery times are long or that customs costs are incurred for import. Unfortunately, a .ch domain is no guarantee that the shop actually delivers from Switzerland. A look at the legal notice often provides certainty. At this point, we at Vibraplast would like to emphasise that our foam online shop is happy to deliver to private individuals and is unparalleled in terms of selection, conditions and availability. For all those who want to buy foam cheaply, we recommend our outlet area. Of course, there are also other suppliers who have a good range of products, but why go far afield when the good stuff is so close?

Foam wholesale

Foam wholesalers are aimed at larger B2B business customers. The advantages of this channel lie in the product range and the advice provided. In addition, individual wishes can be taken into consideration. Last but not least, this channel can offer good volume conditions and also provide customised logistics solutions if required. We would also like to take this opportunity to emphasise our services as a foam wholesaler and foam supplier. Our product range, logistics, price structures and advice are ideally tailored to the needs of demanding business customers. If you have any requirements in this respect, we look forward to hearing from you on Tel: +41 (0)52 368 00 50

Customised foam

There are countless areas of application for foam. As a result, customers' requirements are also diverse in terms of size and shape. As cutting foam to size is a difficult task without the appropriate machine tools, we and other suppliers offer customers a ‘customised foam’ service. Over the years, Vibraplast has developed a range of sophisticated and high-precision customised foam cuts. You can obtain a wide range of products in every possible shape and size. Click here to go directly to the customised foam online shop.

Conclusion

As you can see, foam is a true jack-of-all-trades. The areas of application are incredibly wide-ranging and the various materials differ in their properties and characteristics in such a way that almost any foam requirement can be fulfilled. If you still have any questions after this comprehensive illumination or if you have any special requests regarding the available foams, we look forward to hearing from you.

info@vibraplast.ch