When a cold liquid membrane is applied to a substrate it could be considered to be similar to paint. We all know that paint has to dry before it possesses its protective properties. The same goes for waterproofing membranes. However, what you might not know is that there is a difference between drying and curing.
A liquid waterproofing membrane contains a mixture of components. The main component is the solid particles that remain after the solvent or water, if it is a water-based membrane, evaporate off. The special mix of solids provides the membrane with its waterproofing properties. It is in this solid component that properties like flexibility, strength, durability, and adhesive strength, among others, are designed.
The water or solvents are known as carriers. They carry the solid components of the waterproofing membrane evenly through the mix. In other words the solid particles are dispersed through the water. The carrier is also responsible for the ease of application of the membrane to the substrate. Not enough carrier liquid and the membrane will not flow, whereas too much carrier results in an undesirably thin membrane.
The formation of the final film of a waterproofing membrane is a two-step process involving both the carrier and the solid particles. The two phases are known as drying followed by curing. In a water-based waterproofing membrane, for example, the first step is for all the water to evaporate. When the membrane is dry the solid particles come in to contact.
For example, in Wet-seal Enviro-coat, the water evaporates which allows the particles of the carefully designed blend of polymers – latex hybridised with polyurethanes – to come into contact. Now the curing phase can begin where the particles pack together closely and start to join. This joining or chemical bonding is known as curing. When curing is complete all of the solids have formed a mechanically strong film with the final waterproofing properties.
That is why a membrane needs to not only dry, but cure!
Elisabeth Arif – Wet-seal Product Manager