Molecular structure and physical properties of E‐beam crosslinked low‐density polyethylene for wire and cable insulation applications

Abstract

ABSTRACT:Crosslinking of homemade low-density polyethylene (LDPE) was performed by electron-beam (EB) irradiation. The gel content of the EB-exposed LDPE was determined by the solvent-extraction method. The degree of crosslinking was also evaluated by a hot set measuring test. The results obtained from both the gel-sol and the hot set methods showed that the degree of crosslinking was dependent on the deposited energy in LDPE samples. Increasing the absorbed dose increased the degree of network formation. The LDPE with higher molecular weight yielded higher efficiency of crosslinking at the same irradiation dose. The effect of irradiation dose on the molecular weight between crosslinks (M c ), glass-transition temperature, and free volume were calculated. Mechanical test results showed that the tensile strength of the samples increased with increase in the irradiation dose up to 150 kGy and then slightly decreased with further increasing the deposited energy. The elongation at break decreased with increasing the absorbed dose. The results obtained from differential scanning calorimetry exhibited a small reduction in the melting point and the degree of crystallinity of the EB-exposed LDPE samples compared to those of the untreated samples. The effect of crosslinking on the electrical properties of the irradiated samples was insignificant. The dielectric constant of the treated samples remained nearly constant within the irradiation dose range, although the dissipation factor increased slightly with increasing the absorbed dose. The results obtained from characterizing the EB-induced crosslinking of homemade polyethylene, including LH0030 and LH0075, showed the higher molecular weight polyethylene (LH0030) as a preferred option for wire and cable insulation.

Complete relaxation map of polypropylene: radiation-induced modification as dielectric probe

“…A major application of high-energy radiation is cross-linking of insulation; cross-linking to a gel content of 55% was shown to be beneficial for cable insulation [26]. By linking the macromolecules into a network, the toughness, impact resistance, chemical resistance and working temperatures are improved [35]. A second major application of high-energy radiation is sterilization of the medical disposables.…”

Polyethylene crosslinked in different media: structural changes versus dielectric behaviour

“…Crosslinking of polypropylene to a gel content of 55 % was shown to be beneficial for cable insulation [5]. By linking the macromolecules into a network, the toughness, impact resistance, chemical resistance and working temperatures are improved [6]. Crosslinking enables a thermoplastic polymer like PE to exhibit viscoelastic behaviour, a characteristic of an elastomer at temperatures above the crystalline melting temperature of the thermoplastic.…”

“…In each of these applications, the environment can significantly differ, so maximum reliable service will require a thorough understanding of the environment effects on radiation-induced changes in this material. The overall radiation chemistry of PE and its mechanisms were investigated in detail and several comprehensive reviews are available on this topic [3,5,6,[8][9][10][11].…”

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

“…There exist several methods to produce crosslinked polymers, such as chemical methods, using mainly peroxides 22 or silanes, 23,24 and high-energy irradiation (electronic beam) techniques. [25][26][27] A detailed description of the various crosslinking processes has been given in a comprehensive review by Lazar et al 28 Thermochemical crosslinking involving organic peroxides is most widely used for its controlled decomposition rate, minimal side products, and economical process. 29 Peroxide is incorporated into the polymer, at the time of mixing, below the activation temperature of the peroxide.…”