Preparation Methods
The first PEX material was prepared in the 1930s, by irradiating the extruded tube with an electron beam. The electron beam processing method was made feasible in 1970s but was still expensive. In the 1960s, Engel cross-linking was developed. In this method, a peroxide is mixed with the HDPE before extruding, the cross-linking taking place during the passage of the melted polymer through a long heated die. In 1968, the Sioplas process using silane was patented, followed by another silane-based process, Monosil, in 1974. A process using vinylsilane followed in 1986.
Read more about this topic: Cross-linked Polyethylene
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