Polyurethanes are produced by reacting polyols and isocyanates.
PolyolsBoth polyols and isocyanates are often derived from crude oil. However, as part of the industry’s commitment to sustainability, some polyols can be derived from renewable sources, thus increasing renewable content of PU foams. These are called bio-based or Natural Oil Polyols (NOPs), where a chemical multi-step process is typically required for the conversion of the natural oils into bio-polyols to make them similar to conventional fossil-based polyols. Other alternative polyols include: recycled polyol (re-polyol), CO2-based polyether polyols and PU raw materials from mass-balance approach.
IsocyanatesMDI (Methylene diphenyl diisocyate) and TDI (Toluene diisocyanate) are the prefered aromatic diisocyanates used for manufacturing of polyurethane foam in Europe. When mixed with polyols, these substances react instantly and form the building blocks of polyurethane.
AdditivesVarious additives are added to the foam formulation to generate high-end foam quaility and required foam physical properties according to OEM specifications.
- Catalysts are used to increase the reaction rate between diisocyanates and polyols. There is a wide variety, with metals salts or amine-based catalysts the most commonly used.
- Blowing agent used to produce the foam’s cellular structure. The blowing agent for flexible polyurethane foam is typically water – generating C02 through reaction with water and isocyanates.
- Flame retardants are added in some instances – notably when required by local legislation – to formulations to increase the fire resistance of polyurethane foam.
- Silicone surfactants are used for cell regulation and cell stabilisation.
- Process aid tools are used to optimise foaming processes.
- Release agents are used to facilitate demoulding of the foam pad from the mould.
METHYLENE DIPHENYL DIISOCYANATE