A cyclophosphazene derivative containing multiple cyano groups, denoted as hexa(4-cyanophenoxy)cyclotriphosphazene (CN-CP), was synthesized by a one-step nucleophilic substitution reaction for a phosphorus–nitrogen flame retardant. To meet the strict requirement of safe and environment-protective insulation materials, a series of composites based on low-density polyethylene-poly(ethylene-co-vinyl acetate) containing CN-CP/Mg(OH)2/Al(OH)3 organic-inorganic synergistic flame retardants was fabricated. High-energy electron beam irradiation was subsequently applied to obtain a halogen-free flame-retardant crosslinked system. The relationship between crosslinking degree and irradiation dose was studied, and crosslinking degrees ranging within 63%–85% were obtained under 100–190 kGy. Furthermore, the effects of CN-CP filler and irradiation dose on the properties of the composites were carefully investigated. The maximum tensile stress and limiting oxygen index values of most composites irradiated by EB were more than 15 MPa and 28%. Results revealed that the obtained materials had excellent thermal and mechanical, flame-retardant, and insulation properties, thereby suggesting their promising prospects for wire and cable applications.

In the current study, the ceramifiable-silicone-rubber-composites (CSRs) containing allyl-functionalized cyclophosphazene (CP-Allyl) were prepared for studying as novel fire-resistant insulating materials. Electron-beam (EB) irradiation was applied to obtain the cross-linked networks, and the gel content of 98.8% could be achieved at an irradiation dose of 120 kGy. The thermal, mechanical, flame retardancy and insulation properties were well investigated, and it was found that the involvement of CP-Allyl could have a great influence on the properties. The tensile stress of the EB-irradiated CP-Allyl containing composite reached 5.2 MPa, and its limiting oxygen index was up to 32.4%. After ablation at 700-1000 C, it was observed that the shapes of the CSR samples could be well maintained, and the hard and integrated ceramic phases were formed. All the studies indicate that these CSRs may be the promising insulating materials for wires and cables.