In this paper, four kinds of nitrogenous bases, adenine (A), guanine (G), cytosine (C), and uracil (U), were used as biobased gas sources to regulate the efficiency of an intumescent flame retardant (IFR) in polypropylene (PP). The flame retardant properties of PP composites were evaluated by using the limiting oxygen index (LOI), the vertical burning (UL-94) test, an infrared thermal imager, etc. The thermal degradation behaviors and char morphology were studied by using thermogravimetric analysis (TGA) and scanning electron microscopy. It is found that U and C play great roles in improving the flame retardancy of PP/IFR composites. The PP sample containing 17 wt % IFR and 1 wt % U (or C) achieves the UL-94 V0 rating without melt-dripping and has a LOI value of >27.9%, while the samples with equal amounts of A or G are not classified in the UL-94 test. TGA results showed that U (or C) can react with an IFR, but the interaction between A (or G) and an IFR is weak. U (or C) accelerates the formation of char and regulates its space structure at the right content. They induce the formation of a cellular and intumescent char layer that decreases the surface temperature quickly after ignition and protects the underlying resin from flame, thus improving the efficiency of PP/IFR composites.
In this paper, nitrogenous bases adenine (A), guanine (G), cytosine (C), and uracil (U), were used to tailor the hydrogen-bonded network of melamine cyanurate (MCA) and were noted as A-MCA, G-MCA, C-MCA, U-MCA, respectively. The results showed that the size, morphology and thermal behavior of MCA are regulated by base due to the formation of hydrogen bonds between them. These modified MCAs were used to improve the flame retardancy of polyamide 6 (PA6) which was evaluated by using the limiting oxygen index (LOI) and the vertical burning (UL-94) test, etc. The results showed that the PA6 sample containing 9 wt% C-MCA achieves the UL-94 V-0 rating and has a LOI value of 30.7%, while the other samples with equal amounts of MCA only pass the UL-94 V-2 rating. The flame retardant mechanism was studied, and the results reveal that C-MCA with smaller size has greater contact area with PA6 which helps to catalyze the decomposition of PA6; Thus the PA6/C-MCA releases more NH 3 , CO 2 etc., and produces more droplets than others, which dilutes combustible gas and takes away heat to make the samples extinguish.
危险品化学品经营许可证（带存储）