bridges are posed on lines that are both orthogonal to diamond base bonds and parallel to faces of c. Almost all cross-linkable polyethylene compounds (XLPE) for wire and cable applications are based on LDPE. XLPE-insulated cables have a rated maximum conductor temperature of 90 °C and an emergency rating up to 140 °C, depending on the standard used. They have a conductor short-circuit rating of 250 °C. XLPE has excellent dielectric properties, making it useful for medium voltage—1 to 69 kV AC, and high-voltage cables—up to 380 kV AC-voltage, and several hundred kV DC. Numerous modifications in the basic polymer structure can be made to maximize productivity during the manufacturing process. For medium voltage applications, reactivity can be boosted significantly. This results in higher line speeds in cases where limitations in either the curing or cooling processes within the continuous vulcanization (CV) tubes used to cross-link the insulation. XLPE insulation can be modified to limit the amount of by-product gases generated during the cross-linking process. This is particularly useful for high-voltage cable and extra-high voltage cable applications, where degassing requirements can significantly lengthen cable manufacturing time. Preparation methods Various methods can be used to prepare PEX from thermoplastic polyethylene (PE-LD, PE-LLD or PE-HD). 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 the 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 silicon hydride (silane) was patented, followed by another silane-based process, Monosil, in 1974. A process using vinylsilane followed in 1986. Types of crosslinking A basic distinction is made between peroxide crosslinking (PE-Xa), silane crosslinking (PE-Xb), electron beam crosslinking (PE-Xc) and azo crosslinking (PE-Xd). Shown are the peroxide, the silane and irradiation crosslinking. In each method, a hydrogen atom is removed from the polyethylene chain (top center), either by radiation or by peroxides (R-O-O-R), forming a radical. Then, two radical chains can crosslink, either directly (bottom left) or indirectly via silane compounds (bottom right). Peroxide crosslinking (PE-Xa): The crosslinking of polyethylene using peroxides (e. g. dicumyl peroxide or di-tert-butyl peroxide) is still of major importance. In the so-called Engel process, a mixture of HDPE