New phosphorus- and nitrogen-containing poly(methyl methacrylate)-based copolymer
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Pure poly(methyl methacrylate) (PMMA) always exhibits high flammability and low thermal stability. To address that, a novel reactive comonomer containing phosphorus and nitrogen elements, 4-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl) phenyl diethylphosphoramidate (PDM), was successfully synthesized and then introduced into PMMA matrix through emulsion copolymerization method. The structure of PDM and as-obtained poly(MMA-co-PDM) copolymers was characterized using Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance spectroscopy (1H NMR) and 31P NMR. From thermal gravimetric analysis and microscale combustion calorimeter, the poly(MMA-co-PDM) copolymers exhibit significantly enhanced flame retardancy and thermal stability, such as the higher degradation temperatures, and decreased peak heat release rate (maximally by 24.1%) and total heat release (maximally by 22.1%). The glass transition temperature (Tg) values of poly(MMA-co-PDM) copolymers obtained by differential scanning calorimetry slightly decrease as the raising flexibility of polymer chain. The char residue analysis by scanning electron microscopy and FT-IR demonstrates that the incorporation of PDM can catalyze the charring of copolymers in condensed phase and form an excellent thermal stability char residue with aromatic structure, further preventing the inner substrate from further combustion. The detailed mechanism was proposed.
KeywordsPoly(methyl methacrylate) based copolymer Flame retardancy Thermal property Mechanisms
This work was supported by the National Natural Science Foundation of China (No. 21704111), the Science and Technology Program of Guangzhou (No. 201806010113), the Financial Support from China Scholarship Council and the Fundamental Research Funds for the Central Universities.
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