Article 3: Specialist Application of Polyurea
Over the previous months CSC Services have been focused on conveying the range of applications and adhesion characteristics of Polyurea technology.
In this series of articles Mark Lemon, Managing Director of CSC Services looks at the important reasons why approved and trained installers are required for such technology.
This article examines the three key variables associated with the application of polyurea. Applicators should fully understand the dynamics of pressure, temperature and flow to ensure correct use of the specialist application equipment.
Polyurea is obtained following the chemical reaction between the polyamine and the isocyanate at a temperature that can vary between 50° and 80°, a pressure of application between 150 and 200 bars and a mixing ratio by volume suitable variable according to the specifications of the manufacturer, but which generally occurs in the ratio of 1:1.
The pressure and temperature are two variables that must be carefully met in order to optimise the spraying and the reaction necessary to reach the final mechanical and chemical properties of the polyurea.
As the Polyurea Development Association Europe sets out in its Good Code of Practice these products are generally supplied in standard 200 litre drums sealed to avoid contact with the air. The drum of resin (component B) usually has a lid with the same diameter as the drum, while that of the isocyanate (component B) is totally closed with the exception of a two-inch valve for the insertion of the pump and a nozzle for the insertion of the dehumidifying filter.
Pumps that transfer the product from the drums to the machine (for mixing) are mounted on both of them. The drums can be heated with the bands.
The polyamine/polyol (B) requires agitation in order to homogenise the internal pigments and at the same time reduce any extremes of viscosity.
The isocyanate (A) is extremely sensitive to moisture; therefor special attention is required when using it to avoid any contact with the air. It is good practice to provide a system for reduction and control of moisture. This is generally accomplished through the use of a special filter with desiccant salts placed directly inside the drum cover.
Another important variable in the application phase, which must be suitably calculated according to the type of work done is the flow rate. This usually varies between ¾ litres per minute until reaching over 10 litres per minute to obtain greater thickness of polyurea per unit of time.
The Polyurea Development Association Europe clearly states in relation to the application of Polyurea:
“In order to withdraw the fluids, then heat, pressure, transfer and mix them properly for long periods of time, there is a clear need to have properly configured specialised equipment, able to ensure the achievement and maintenance of the listed values, temperature, pressure and flow rate, regardless of conditions such as environmental temperature, relative air humidity, distance from the point of application.”
Using a specialist contractor who has the correct equipment and has been fully trained in how to operate this is of critical importance to the success of a polyurea system.