The thermal decomposition and flame-retardant physical characteristics of specimens are explained via the limiting oxygen index (LOI), cone calorimeter, smoke density, and thermogravimetry analysis (TGA) tests. The outcomes of TGA, smoke emission, and LOI tests showed that thermal strength and flame-retardant characteristics of the specimens containing magnesium hydroxide (MH) have superior thermal strength compared with the similar specimens containing alumina trihydrate (ATH). The flame-retardant characteristics and thermal strength of specimens were boosted upon radiation and the development of cross-linking bonds in the polymer structure. The smoke density tester results present that MH specimens generate the least smoke density associated with the pristine low-density polyethylene and the similar ATH specimens. This study proved that the inclusion of MH and radiation of specimens generated greater thermal strength and flame-retardant characteristics compared with the inclusion of ATH to radiated specimens. These successes are right and proper for cable companies to deliver halogen-free flame-retardant cable materials. © 2019, Central Institute of Plastics Engineering & Technology.