ORIGINAL PAPER Surface modification of magnesium hydroxide nanoparticles with hexylphosphoric acid to improve thermal stabilities of polyethylene composites Juran Noh 1 • Insung Kang 1 • Jaehyuk Choi 1 • Hira Fatima 1 • Pil J. Yoo 2 • Kyung Wha Oh 3 • Juhyun Park 1 Received: 15 August 2015 / Revised: 28 December 2015 / Accepted: 15 February 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract Magnesium hydroxide (MH) has been identified as an alternative flame retardant for polyethylenes (PEs), to replace halogen-based flame retardants, which cause severe environmental problems. However, the use of MH in fabricating composites with PEs is limited because a high loading ratio is required for adequate flame suppression and because the hydrophilic surfaces of microparticulate MH cause aggregation in hydrophobic, highly crystalline PEs. To overcome these issues, we modified the surfaces of MH nanoparticles using hexylphosphoric acid to obtain hydrophobic surfaces. The surface-modified MH nanoparticles enhanced the ther- mal stabilities of PE composites, even at a low loading ratio of below 30 wt%. It was attributed to the uniform dispersion of magnesium hydroxide nanoparticles by increased association between the hexyl moieties and short alkyl side chains in polyethylenes together with the synergetic effect of the endothermic decomposition reaction of magnesium hydroxide and radical capture by phosphorus moieties. Keywords Polyethylene Á Magnesium hydroxide Á Phosphate Á Flame retardant Á Surface treatment & Juhyun Park jpark@cau.ac.kr 1 School of Chemical Engineering and Materials Science, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Republic of Korea 2 School of Chemical Engineering and SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea 3 Department of Fashion Design, Chung-Ang University, Seoul 06974, Republic of Korea 123 Polym. Bull. DOI 10.1007/s00289-016-1628-0