The flexible polyurethane foam industry – as any industry really – uses a vocabulary of its own. In this section you will find answers to frequently asked questions and more explanations on some of the terms used in the flexible foam industry. For more information on polyurethanes in general, please visit Polyurethanes.org

What are foam blocks?

EUROPUR members manufacture polyurethane foam through a continuous slabstock production process. This means that a mixture of polyols and diisocyanates “foams” and rises within seconds on a moving conveyor and then solidifies. This is a continuous process and in theory foam blocks of several kilometres in length could be produced this way. In reality, the foam blocks are typically cut at a length of between 15 and 120m and then stored. Blocks can also be cut into foam rolls for further use.

What are additives?

Additives are substances that can be added to the mixture of polyols and diisocyanates at the time of foam production to be present in the foam and/or to provide it with specific properties. They for example help controlling cell structures, cell opening, odor formation or flame resistance. They can also be added for aesthetic reasons, with pigments for example allowing for foam of any colour to be produced. 

Is polyurethane foam an article, a substance or a mixture under the REACH Regulation?

Polyurethane foam is an article. This view was supported in ECHA’s Guidance on requirements for substances in articles from 2011, which in its page 50 states that: "in the conversion unit, the structure and design of the polymer compoulds is changed. In the resulting material, the design and structure is kept during further processing. For the polymer sector, this means that processes including for example, but not limited to, pipe extrusion, film blowing, blow moulding, sheet forming, rotomoulding, foaming, compression moulding, fibre spinning or tape slitting calendaring, coating or injection moulding mark the ‘red line’ between mixture and article".

 

What is reticulation?

Foam from slabstock production partially contains closed cells. Depending on the application, this may limit their properties. They can therefore be subject to reticulation, which is a controlled explosion of a hydrogen and oxygen gas mixture in a closed reactor. This process melts residual cell membranes and ensures that a completely open cellular network is obtained.

What is impregnation?

Impregnation is another way of instilling foam with specific properties. Contrary to additives, which are added to formulations at the stage of foam production, impregnation takes place at a later stage. The foam is dipped into a bath that contains an impregnation product. It is then squeezed and dried in an oven. Impregnation is typically used for properties such as fire resistance, sealing, weldability or self-support.

What is densification?

Densification is a process of permanent deformation of polyurethane foam by compression and heating. This allows for new cellular materials to be obtained with a higher density, and which are less prone to deformation. 

What are NOP or bio-based PU foams?

Natural Oil Polyol (NOP) polyurethane foams are produced by using in part polyols from renewable sources such as soybean, castor, sunflower, rapeseed oil or a mix thereof. Apart from that, they are manufactured in the same way as traditional foams.

What are composite foams or rebounded foams?

Composite foams or rebounded foams are foams produced from production waste (trim foam) that is “glued” together with diisocyanates. Composite foams are used for example as carpet underlay, for packaging, shoes insoles, or for sport floors. 

Does polyurethane foam contain flame retardants?

Spontaneous ignition of polyurethane foam is not possible under normal operating temperatures. However, being produced from crude oil derivatives, polyurethane foam does have high energy content and can burn when submitted to high heat or a direct flame. Depending on the specifications of customers or national regulations, flame retardants may thus need to be added as additives, for example for upholstered seating in public places such as theatres or cinemas which need to comply with strict fire regulations.

What is fogging?

Fogging is mentioned in automotive applications. It refers to the deposition of volatile compounds coming from interior trim materials on the windscreen and rear window of the car. This notably happens under the influence of high temperatures in the passenger compartment. Low fogging foams are designed to reduce this phenomenon.

What is flame lamination?

Flame lamination is used to produce laminates of foam and fabrics by passing the polyurethane foam over an open flame. The heat melts the upper surface of the foam. This melted layer acts as glue bonding the foam and the fabric.

Flame laminated foams are typically used in the automotive industry for seat covers, headliners and door panels, as well as in the shoe and clothing industry.

Does polyurethane foam smell / have an odour?

Fresh polyurethane foam comes with an odour that can be compared to the smell of fresh paint. This odour disappears within days and usually well before end-products are being placed on the market. Controlling odour is a matter of discipline in raw materials sourcing, production and quality control by the foam manufacturer.