Osmosis

Osmosis is a physical process where a liquid starts to diffuse through a membrane when there is a difference in concentration of certain solutes.

Why is osmosis protection important in a composite laminate?

When a thermoset laminate is continuously exposed to water, water molecules will penetrate through the gelcoat. Depending on factors like material quality, presence of defects, layer thickness and temperature, water may also run into the laminate layers beneath the gelcoat. For example, the skin coat may harbor micro-porosity at the interface of glass fibers and resin, causing capillary movement of water. Water in the laminate will cause degradation and presence of a concentrated acid solution that acts as a catalyst in the degradation process. The concentrated solution causes osmotic pressure and once the pressure is high enough, blisters will appear.

Finishmat^® offers optimal osmosis protection by forming a closed resin layer with low fiber and high resin content directly behind the gelcoat. This allows the resin to cure better and hence blocks water from further penetration into the laminate. The nonwoven fibers have good connection with the resin and do not leave any porosity.