PE-RT II pipes, also known as "Type II Heat-Resistant Polyethylene Pipes (PE-RT II pipes)," are made from high-density polyethylene (HDPE) and copolymers of octene, hexene, and butene (one of the latter). They were originally researched and developed by Dow Chemical Company in the United States and later successfully produced by SK in South Korea and Total Petrochemicals in France, Basel. The full English name for Type II Heat-Resistant Polyethylene (PE-RT II) is "PolyEthylene of Raised Temperature Resistance." PE-RT II is categorized into three types based on different copolymer monomers: 1. Ethylene and Octene Copolymer - Heat-Resistant Polyethylene (C2+C8); 2. Ethylene and Hexene Copolymer - Heat-Resistant Polyethylene (C2+C6); 3. Ethylene and Butene Copolymer - Heat-Resistant Polyethylene (C2+C4).