Non-barrier pex pipe is produced with crosslinked polyethylene. Crosslinking is obtained through a chemical process that increases the bonds between macromolecules to form a more complex stricture than the normal polyethylene. Due to the crosslinking, the polyethylene's performance is greatly enhanced still maintain the excellent properities of thermoplastics Oxygen-barrier pex pipe with evoh is made up of 5 layers: pex, adhesive, evoh, adhesive, pex. The layers of adhesive bind the two layers of pex-b to the central barrier layer of evoh by a thermal reaction. The evoh barrier layer is right in the center, preventing the pipe from being damaged by scratch and from reducing its performance due to moisture. Pe(x, rt)-al-pe(x, rt) pipe are a kind of five-layers' pipe that combines the advantages of a metal and plastic pipes and eliminates the disadvantages of both materials at the same time.The aluminum core in middle layer is absolutely diffusion tight, which can reliably prevents oxygen/gases from permeating into the pipe. The pe(x, rt)-al-pe(x, rt) pipes can compensate and reduce snap-back forces and heat-expansion with changes of