Improved Flame Retardancy and Tensile Property of Aramid Fiber‐Reinforced Aluminum Hydroxide/Zinc Borate/Low‐Density Polyethylene Composites

ABSTRACT Low‐density polyethylene (LDPE) is a preferred material for engineering applications due to its flexibility and erosion resistance. However, LDPE demonstrates inherent flammability with limiting oxygen index (LOI) being around 17.5%. This work aims to enhance flame retardancy and tensile property of LDPE by incorporating aluminum hydroxide (ATH), zinc borate (ZB), and aramid fibers (AF). The reinforced LDPE containing 1.5 wt% AFs exhibits optimal flame retardancy among the samples as tested. Compared to the composites without AFs, the melt flow index of the composites is reduced by 95.5%, the LOI increased by 4.48% and a UL‐94 V‐0 rating is achieved. The thermogravimetric analysis test shows that the final residual mass reaches 44.2%. The cone calorimeter tests reveal the heat release rate is 110.0 kW/m 2 and the smoke production rate is 0.016 m 2 /s, which are declined by 3.7% and 14.3%, respectively. Fourier‐transform infrared spectroscopy and scanning electron microscopy prove that the tensile action of AFs plays an active role in the formation of stable char which is beneficial for flame‐retardant performances. Apart from enhanced flame retardancy, the tensile strength of the reinforced composites reaches an increase of over 50% while meeting flame‐retardant requirements.