Synergistic effects of ammonium polyphosphate/melamine intumescent system with macromolecular char former in flame-retarding polyoxymethylene

Bio-based arginine surface-modified ammonium polyphosphate: an efficient intumescent flame retardant for epoxy resin

In this work, ammonium polyphosphate (APP) was surface-modified by bio-based arginine (Arg) for the first time to enhance its flame retardance for fire-safety epoxy resin (EP). The structure of Arg modified APP (Arg-APP) was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ¹H nuclear magnetic resonance (¹H-NMR), and scanning electron microscopy (SEM). The results illustrated that Arg was attached on the surface of APP through a cation exchange reaction. With Arg acting as the efficient carbon source, the char-forming ability of Arg-APP was significantly improved as illustrated by thermogravimetric analysis (TGA). The flame retardance of EP/APP and EP/Arg-APP composites was evaluated using the limit oxygen index (LOI), vertical burning tests (UL-94), and cone calorimeter tests (CCT). The results showed that at the same weight loading (15 wt%), Arg-APP had better flame retardance and smoke suppression performance compared with pristine APP, which can be attributed to Arg-APP constituting an integrated intumescent flame retardant (IFR) and facilitating formation of char residues with significantly expanded structures and higher carbonization degrees. When the weight loading of Arg-APP reached 25 wt%, the EP/Arg-APP composite could achieve an LOI value as high as 34.7%, pass V-0 requirements in UL-94 tests, and decrease the peak heat release rate and total smoke production by 83.5% and 61.1% compared with neat EP in CCT, respectively, indicating the superior flame retardance performance of Arg-APP. Finally, the effects of the flame retardant additives on the mechanical properties of EP were evaluated by the differential scanning calorimetry (DSC) tests and tensile-strain tests. At the same additive weight loading (15 wt%), the EP/Arg-APP composite showed higher glass-transition temperature and better tensile-strain properties compared with EP/APP composite, which can be attributed to the Arg shell structure improving the compatibility between APP and the organic substrate. In conclusion, this work presents a convenient and environmentally friendly method to improve the practical performance of APP.

Arginine modified ammonium polyphosphate was prepared through the cation-exchange reaction and applied as an intumescent flame retardant for epoxy resin.

Recent studies on the decomposition and strategies of smoke and toxicity suppression for polyurethane based materials

This review provides insight into recent studies related to thermal degradation, smoke and toxicity production and their reduction strategies for polyurethane-based materials.

Influence of morphology on the flame retardancy of polystyrene/nylon-6/ammonium polyphosphate/clay blends

Ammonium polyphosphate (APP) and clay were utilized to flame retard polystyrene/nylon 6 (PS/PA6) blends. X-ray diffraction and transmission electron microscopy (TEM) results showed that clay formed exfoliated structures in PS/PA6/APP/clay. The results of Fourier transform infrared spectra and TEM indicated that APP and clay were exclusively dispersed in the PA6 phase. The influences of the distribution of APP and clay in PS/PA6 blends and the continuity of the (PA6 + APP) phase on flame retardancy were investigated. The flame-retardant properties were evaluated by limiting oxygen index (LOI), vertical flammability test, and cone calorimeter tests. For blends with a continuous PA6 + APP phase, the decrease of PA6 content caused an increase in LOI values from 26 to 34% and a remarkable reduction of the heat release rate. Results of thermogravimetric analysis indicated that the localization of APP and clay in the PA6 phase caused an increase in APP concentration in the PA6 phase with decreasing PA6 content, resulting in the rapid formation of intumescent charred layer, which augmented the flame retardancy. The transformation of (PA6 + APP) phase morphology from a continuous state to a discontinuous state at a PA6 content of below 40% (w/w) was observed. Meanwhile, the flame-retardant properties were decreased as the PA6 content decreases. The discontinuous intumescent charred layer thus formed and the inhibiting action of clay on the residue char from expanding could be responsible for the deterioration of flame-retardant properties, which were also confirmed by scanning electron microscopy and the aspect of intumescent charred layer.