Reactive, Intumescent, Halogen-Free Flame Retardant for Polypropylene

A reactive, intumescent, halogen-free flame retardant, 2-({9-[(4,6-diamino-1,3,5-triazin-2-yl)amino]-3,9-dioxido-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecan-3-yl}oxy)ethyl methacrylate (EADP), was synthesized through a simple three-step reaction from phosphorus oxychloride, pentaerythritol, hydroxyethyl methacrylate, and melamine. EADP exhibited excellent thermal stability and char-forming ability, as revealed by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The TGA results show that the temperature at 5% weight loss was 297.8 degrees C and the char yield at 700 degrees C was 51.75%. SEM observation revealed that the char showed a continuous and compact surface and a cellular inner structure with different sizes. Composite of polypropylene (PP) with a 25 wt % addition of EADP (PP/EADP25) passed the UL-94 V-0 rating and showed a limiting oxygen index value of 31.5. Compared with those of neat PP, the flexural strength and modulus values of PP/EADP25 were somewhat improved, the tensile strength was basically unchanged, and the notched Izod impact strength was slightly decreased. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40054.