PEX pipe is short for high density polyethylene, which is made from HDPE. HDPE usually comes in pill-size granules, which are melted inside the extruder during the manufacturing process and pushed through a die under pressure, thuse creating a pipe.
PEX is the short terms for cross-linked (hence, "x") Polyethylene and created during the extrusion process by forming links between molecules. Cross-linking process improves the chemical and temperature performance ratings of the polymer, gives it flexibility and extra strength.
Types of PEX pipes:
All PEX is generally divided into three main types: PEXa, PEXb and PEXc. It is a misconception to think that one type is better than the other simple because it's an a, b, or c type. These letters are used to identify the manufacturing process and have nothing to do with quality of performace ratings.
PEXa pipe is produced using Peroxide(or, "Engel")method, named after the inventor Tomas Engel. During the manufacturing process, free radicals are created when HDPE polymer is melted and cross-links between molecules occur at temperatures that exceed the decomposition temperature of the polymer. Some of the manufacturers who make this type of PEX are: Uponor， Rehau and Mr. PEX; China suppliers such as Hongyue.
PEXb is made using a "Silane" method of cross-linking, where links between the molecules of the HDPE form after the extrusion process using a catalyst and exposing PEX tubing to water. This type of PEX is the most common and is manufactured by a large mumber of companies, such as: Viega, Watts, Bow, Everhot, Zurm etc. Supplier from China such as Hongyue, Rifeng, Kingbull, Palconn etc.
PEXc is manufactured using "Electronic irradiation" method of cross-linking, also known as "Cold" cross-linking. Here, cross-linking of the molecules is done after the process of extrusion by exposing the pipe to an electron radiation beam. The radiation emitted allows to break the existing links between molecules of the polymer and initiate cross-linking process.
Weifang kaide Plastics Machienry Co., Ltd are professional for PEXa and PEXb pipe extrusion line manufacturing, especially for PEXb pipe line.
Any inquiry is warmly welcome here, www.extrudermachinery.com.