A: I am asked this question often and at first glance it does seem to be rather complicated. "Ambient" temperature in Alaska is obviously quite different from "ambient" temperature in South Texas.
First and foremost though, what we are talking about in this case is the operating temperature of the pipeline once it is in service. The temperature at which a pipeline will operate is incredibly important. As you would expect, if a pipeline is operating at an elevated temperature, it is fair to assume that the sealant of the shrink sleeve will be operating at a temperature very close to the pipes operating temperature. Sealants in general (be they mastic or hot melt adhesive) will tend to have different physical properties based on the temperature at which they operate.
Add in things like soil stress, pipe movement and pipe expansion and the physical properties of the sealant become highly critical.
In our world, we look at WPCT and TPS as our ambient temperature coatings. They are designed to be used on pipelines that will operate at or below 108F (40C). Again, they can be installed while temperatures are higher than that; but once buried, the operating temperature of the line needs to be at or below the 108F.
To speak even further to that; shrink sleeves designed to operate at ambient temperatures should not be installed on pipelines that will be located above ground in direct sunlight (permanently). This has nothing to do with UV resistance (all sleeves are UV resistant due to the carbon black in the backing formulation). In fact, the sleeves cannot be permanently installed above ground in sun light because black body temperatures from the sun can regularly exceed 108F (sometimes reaching has high as 180F).
There you have it. More than you ever could have wanted to know about ambient temperature!