Tags: #buildingenclosures #buildingenvelopes #buildingscience #materialsscience #roguetesting

Which one of these is least like the others? When it comes to water absorption, how we think a product performs may not align with reality.

These seven-day sorption curves show how some sealants/liquid flashings perform counter to the ‘norms’ of their respective class. Sometimes an STPE behaves as a silicone and a silicone behaves as a polyurethane. And it’s relatively easy to find STPEs that behave as polyurethanes. 

When we test these products using conventional water sorption methods, we typically do so for a mere 24-hr test period (ASTM D570). And we fail to see how one product stands apart from the others. Clearly, 24 hours is simply too short. I go further rogue by continuing to monitor at 14, 21, and 28 days – but that’s where things get keenly interesting. A topic for another post. 

We routinely embrace 7-day immersion in adhesion testing (AAMA 711/714). This test duration is reasonable because it reflects what sometimes occurs in the real world. But unfortunately, we never get to see those post-immersion adhesion data. We only see the ‘pass’ score. That’s disappointing. 

And so I ask, why don’t we adopt 7-day sorption curves to align with adhesion testing following 7-day immersion? That’s a rhetorical question.