There are too many types of plastic to list, each with its own properties. Many of them are resistant to oils, but there are others that can be degraded by oil based materials. Dye penetrants of all kinds are oil based and can interact with certain plastics.
Best regards - Al
Tim
The pipe was Ductile Iron. The leak was reportedly in a gasket. When I got toward the end where we were putting the freon in, I thought that the leak I detected came from leakage in the filling operation, which I picked up because I was downwind. I figured that the method failed. However, when I passed the second joint coupling, the alarm went silent. The contractor called up the back hoe, and a few operating engineers, and dug up the second joint area. They didn't even get the whole joint uncovered when they saw the wet sand. Everyone was extremely happy.
By the way, I believe that the freon method is probably illegal now. However, If I were faced with 8000 feet of back filled and tamped pipe to dig up along a busy road, I would probably ignore that law.