Study On Preparation And Chemical Cross-Linking Kinetics Of Halogen-Free Fire-Retardant Polyolefine Cable Materials

Flame retardancy of insulation and sheathing materials for wire and cable has become a matter of urgency because these materials inherently flammable can trigger combustion in a certain temperature and oxygen concentration. Due to the potential environmental pollution caused by halogen cotaining fire retardant, the study on halogen-free fire retardant polyolefin compounds for wire and cables has attracted much attention.This paper studied the development of chemical crosslinking halogen-free fire retardant polyolefin cable compounds. The mechanical properties, fire retardant properties, thermal stability and thermal distortion resistant properties of chemical crosslinking EVA/LLDPE/ATH composite were evaluated by tensile test, LOI test, thermal aging test and hot set test. The effects of crosslinking temperature, crosslinking agent dosage (DCP) and crosslinking time on the gel content, mechanical properties and thermal stability of the composites were discussed. The results showed that the mechanical properties, fire retardant ability, thermal stability and thermal distortion of the composites with moderate crosslinking degree were significantly improved. Based on these results, chemical crosslinking halogen-free flame retardant cable compounds complying with the requirements of the national standards were obtained.The crosslinking reaction kinetics of halogen-free fire retardant polyolefin system was studied. The activation energy (E_a) and collision factor of crosslinking reaction as well as chemical crosslinking reaction order (n) were calculated according to the Arrhenius equation. The result showed that the activation energy was 122.8kJ/mol, the collision factor was 6.1×10¹³, the chemical crosslinking reaction was a first-order reaction. Meanwhile, the thermal degradation process of crosslinking polyolefin system was investigated by thermogravimetric analysis (TG). The degradation activation energies of crosslinking systems calculated by Kissinger method and Ozawa method were 176.96kJ/mol and 178.63kJ/mol, respectively. Both results were higher than that of uncrosslinked system.