Article 1: Polyurea – Substrate Diagnosis
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 first article looks at why a specialist knowledge of the substrate that the technology is to be applied to is required to ensure successful application.
Polyurea applications can be made on to both new and existing substrates. Installers will need to check every aspect before proceeding with an application of polyurea. Due to the nature of the application and all of the different elements involved, the Polyurea Development Association Europe recommends that all important information on the various steps of the application are correctly documented in a spray log document. Full training should be given to operatives on compiling and using this document.
Whether the substrate is new or existing, it will be necessary to monitor a number of parameters that are critical to the success of the operation, in particular:
- The thermo-hygrometric conditions of the substrate and the environment
- Mechanical conditions of the substrate (tear resistance for concrete substrates.)
Verification of thermo-hygrometric conditions
The thermo-hygrometric conditions are a fundamental parameter and these require careful analysis before the application of the polyurea.
Due to the criticality of the system and its high rate of polymerization, the salient feature of this type of formulation, it is critical to control all aspects related to this point.
Awareness of the existence of condensation, dew or moisture in the substrate is essential. These factors cause the pinholes that create micro-craters on the coating, compromising its water-tightness as well as issues with adhesion.
Monitoring the moisture both on the surface and inside the substrate will influence choices on the most appropriate adhesion promoter or primer.
Knowing the dew point tells you whether you are in operating conditions; it is essential that the surface temperature should be at least 3° above the dew point.
Before applying a polyurea system, especially on concrete, it is necessary to check the resistance to tearing of the substrate itself, as the polyurea is very strong and can cause delamination of the substrate if it is particularly inconsistent.
Adhesion testing should always be done to a standard, otherwise values are not comparable and thus not reliable. The industry uses for ‘pull-off’ the following standards ISO4624 or ASTM D4514. In the standard two different sizes of dollies are mentioned, 20mm and 50mm. The 20mm dollies are suitable for homogenous substrates such as metals and the 50mm dollies are used for less ‘uniform’ substrates such as concrete.
Our next article in this series will look at how the preparation of the surface to which the polyurea system is to be applied is critical to the final success. The three key variables associated with polyurea application and the requirement to manage the dynamics of each will be explored in the third article of this series. The final article will look at how the conclusion of any physical work installing a polyurea system should include verification of contractual specifications.