Polyurethane or polyurea? Which to use?

HISTORY

In 1937, the research director, Otto Bayer, was working on the development of a synthetic fibre similar to the polyamides. During his experiments he used a reactive group which formed urethanes on contact with alcohol - and so polyurethanes were born. Initially however, no one knew what use to make of them, until 10 years later when the foundations were laid for current polyurethane foam products thanks to the invention of the first processing machine.    In 1979 the first foam specifically developed for building insulation was formulated. 

The initial polyurethane membrane was subsequently developed as a product specifically designed for continuous and completely adherent waterproofing. This process revolutionized waterproofing techniques by offering a system with no joins, which could be adapted to any surface shape whilst providing excellent mechanical properties and long lasting durability. It was a significant improvement on existing acrylic systems, which presented difficulties when applied to flat areas     (slope 0)

It wasn’t until the 1990’s that Mark S Barton and Mark Schlichter developed and patented two-component polyurea. Its quick drying properties and resistance to moisture made it ideal for large surface area waterproofing projects.

COMPOSITION

POLYURETHANE

Polyurethane membrane is formed by the reaction of an isocyanate and a polyol in the presence of a catalyst. Polyurethanes represent one of the most versatile polymer families around; depending on the polyol and isocyanate used, it is possible to obtain an infinite range of products, from the most rigid to the most flexible, with polyurethane membranes making up the latter end of the scale. 

POLYUREA

Polyurea is the product of a union between an isocyanate and various polyamines. In contrast to polyurethane it does not require a catalyst, as the union is stronger and faster with double chemical bonds.   It is resistant to high temperatures and moisture (the membrane may even form under water), although it is essential that the surface is dry to ensure proper adherence.   

CHOICE OF PRODUCT

Finally we come to perhaps the most interesting part:  

WHICH IS THE BEST PRODUCT FOR YOUR NEEDS?

To give the correct answer, and compare the two types of membrane, we will take the example of 2 of our best selling products:

• DESMOPOL aromatic polyurethane for cold application
• TECNOCOAT P-2049: 100% pure polyurea for hot application 

These are two waterproofing membranes which present very different chemical and mechanical properties. Due to their characteristics, cost and application methods they are designed for different purposes. 

The first questions we need to ask are these: what type of surface requires waterproofing? Do we have spraying equipment available? Can we reach the surface with this equipment? What are the requirements for the job? What is the budget?....after answering these questions, and with the following table as  a guide, we will be able to make  a decision on the product best suited for our purposes: