Thomas Edison. Thomas Alva Edison (February 11, 1847 â October 18, 1931) was an American inventor and businessman, who has been described as America's greatest inventor. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and the long-lasting, practical electric light bulb.
Pipe dope, or pipe joint compound, is a gooey compound used to seal the connection between threaded pipes and fittings. Because the threads in pipes and fittings still leave an air gap between the two surfaces, the gap must be filled to make it water tight (or gas tight for gas lines).
Generally speaking there are 3 different densities used to manufacture. polyethylene pipe. High Density polyethylene is commonly referred to as HDPE or 3408. The. molecular structure of HDPE is such that there is very little side branching in the. molecular chains that make up the HDPE resin. This resin is more dense than. other resins, therefore it requires relatively less raw material to obtain a specific. pressure rating for the pipe. Medium Density polyethylene is commonly referred to as MDPE or 2406.