In one of my prior careers, I was the Quality Mgr at a PVC pipe extrusion plant. In that role, I was involved with UL testing, NSF testing, R&D experimentation and daily production, including storage. We did include UV inhibitors in our formulations. When the inhibitors were missing or insufficient, the Texas sun would turn the pipe dark brown within 24 hours. Pipe in our inventory yard for more than roughly 6 months would begin to brown and could not be sold. This discoloration occurred on joints that were on the outside of the packs and the exposed ends of interior joints. It was clearly the UV, not the heat that caused the discoloration.

We had ongoing R&D efforts to attack the brittleness issues and determined that heat was a major contributor to this characteristic. One practical example again occurred in the pipe yard where the joints interior to the packs became brittle at a more rapid rate than the exterior joints. Developing an effective formulation without this characteristic would have been a market breakthrough. We did it and sold a lot of it.

From this experience, we recommended any opaque water based paint for UV exposed residential locations.

Darrel Hood
DILIGENT PROPERTY SERVICES