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IMPAG AG
Performance Chemicals

Beat Windler
Räffelstrasse 12
8045 Zürich, Switzerland

Performance Chemicals


21.01.2021

Polyurethanes (PU) – From versatile building blocks to energy savers

Invented in the 1930s, polyurethanes (PUs) have found their way into nearly every aspect of our modern lives and are certainly one of the most, if not the most versatile category of polymers. To name just a few applications, PUs are in the shoes we walk in, the cushions we sit on, the mattresses we sleep on and the textiles we wear, and can be found in paints, coatings, adhesives and insulations for walls and roofs. 
How can such a complex range of plastics all be in the one category, as one commodity? Let’s start with a closer look at the polymeric building blocks…

PUs softness is largely determined by flexible and long-chained polyols (polyethers or polyesters) (B).

 

Its hardness and stiffness, on the other hand, are determined by the structure of the isocyanate (C).

 

In industry, most of the time, rigid aromatic diisocyanates such as MDI and TDI are used (D). The rigid segment can be further influenced by including so-called chain extenders in the form of low molecular weight diols or diamines. These can generate extra spatial freedom, enabling the formation of a highly ordered quasi-crystalline structure of the urethanes. 
To avoid the dangerous handling of highly volatile diisocyanates, it is possible to use pre-polymerized polyols and diisocyanates instead, which only require a final crosslinking step.
In order to yield a homogenous material, it is common to use surfactants to assure mixing of the polar polyol phase and the non-polar and dense polyisocyanate phase. Catalysts are added to enhance the reaction rate.

Reacting aromatic polyester polyols and MDI at the right percentage produces rigid PU foams, which account for 50% of all PU foams manufactured. Rigid foams are typically used as insulation materials in the construction sector, in appliances and, to a lesser extent, for pipe and tank insulation. In construction, insulation is of great importance for

  • keeping indoor temperatures stable
    The insulation material acts as a physical barrier to reduce thermal transmittance between the inside and the outside. Typically, insulation is installed on the walls, roofs and floors of a building.
     
  • saving energy, emissions and costs
    There is a simple rule of thumb: the better a building is insulated, the less energy is needed to heat or cool it and, thus, the less emissions are generated in doing so. Therefore, having a well-insulated building is an excellent way to achieve energy efficiency and even reduce maintenance requirements.
     

This leads us to the final question: what makes rigid PU such an excellent insulator?

  • Among all materials, PU provides the best insulation performance per unit thickness.
  • PU is a two-component system, which grants a certain flexibility in when and where PU can be produced.
  • The raw materials are all commodities available at relatively low cost.
  • The building blocks of PU can be “fine-tuned” to meet specific application requirements.
     

Our product range

  • Triethylenediamine (TEDA)
    Catalyst for PU foams and elastomers
  • Triethylphosphate (TEP)
    Halogen-free flame retardant for PU foam
  • Tris(2-chloroisopropyl) phosphate (TCPP)
    Flame retardant for soft and hard PU foam
  • Chlorinated paraffins (CLP)
    Flame retardant for one component PU foam (solid and liquid) 
  • Biochek 8070 PFB based on the actives TBZ and BIT
    Biocide on polyetherpolyol carrier for PU soft foams
  • p-Toluene sulfonyl isocyanate (PTSI)
    Scavenger for water/isocyanate reactive compounds
  • Poly(tetramethylene ether) glycol (PTMEG)
    Polyol for production of, among others, PU textile fibres
     
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