By Scott Kelly, Technical Consultant
When to Use Hydrophilics
Prime Resins offers great hydrophobic products we could sell for all kinds of applications, if that’s all we were concerned about (the sell). But the truth is, hydrophobics should only be used when water flow is high and you need rapid, high volume expansion to seal a leak. Once the leak is manageable, it can be fixed permanently with a hydrophilic resin like Prime Flex 900 XLV.
Let me start by saying all products are not created equal. Many manufacturers use solvents to lower the cost and the viscosity of the resin. When that solvent evaporates out during the chemical reaction and after the cure, it leads to shrinkage. Some manufacturers have up to 22% solvent content in their hydrophilic formulas. That’s 22% of the volume guaranteed to be gone after cure. They are also posted flammable for that reason. The speed of the reaction is also important. Fast reacting formulations result in a cell structure that is highly filled with large gas bubbles, creating high pressure within the cells of the foam. It’s natural for areas of high pressure to acclimate over time or equalize with lower pressures outside. The result is off-gassing and a large loss of foam mass (i.e. shrinkage). With solvent-heavy resins, the cause of shrinkage is more likely attributable to these two issues than to simple dehydration.
Prime Flex 900 XLV expands slowly and is hydrophilic during the initial reaction and the expansion, gobbling up water molecules. During the finishing stages of the reaction almost all water inducted is used up. After that point you have closed cell foam that is 80% gas, 15 % polyurethane, and 5 % water. Once the foam is cured it has more of a hydrophobic character from a water absorption standpoint. Therefore, hydration or dehydration is minimal.
It is also very important that the foam grout is installed under compression. The area needs to be sealed off at the surface and then injected so that the foam is restricted during expansion. This creates dense foam that is very resilient. If you have any questions about the proper use of polyurethane resins, feel free to comment below or contact us for more information.