Utilizing The Dispersion Of Montmorillonite And Ammonium Polyphosphate To Improve Flame-retardant Properties Of PS/PA6Blends

In the recent years, the investigations of the flame retardation in polymer blendshave been focus on developing the new kinds of flame retardants or investing thesynergistic effect in different flame retardants, and there are few researchesinvestigating the distribution of flame retardants in the blend to improve flame-retardant properties. In this paper, we firstly studied the effect of distribution of flameretardants ammonium polyphosphate (APP) and organic montmorillonite (OMMT) inthe PS/PA6blends and the morphology of blends on their flame-retardant properties.The results of the fourier transform infrared spectroscopy (FTIR) and transmissionelectron microscopy (TEM) show that APP and OMMT were both dispersed in thePA6phase selectively. Flame-retardant properties of the blends with differentmorphologies were investigated. When PA6phase was formed the continuous phase,the contents of APP and OMMT in PA6phase increased with the decreasing content ofthe PA6phase, which is benefited to the formation of the carbon layer, resulting in theimprovement of the flame-retardant properties. When the morphology of PA6phaseconverted from continuous phase to dispersed phase, the flame-retardant properties ofblends decreased significantly even though the content of APP and OMMT in PA6phase will be improved. The results of TG, Cone Calorimeter and SEM showed thatdispersed PA6phase was not conducive to the formation of the continuous carbonlayer, leading to the decreasing of the flame-retardant properties of the blends.Meanwhile, in the paper, polymer blends was achieved by the method thatpoly(styrene-co-maleic anhydride)(SMA) was first reacted with OMMT, and thenblended with PA6/PS. The influences of the distribution of OMMT and themorphology of PS/PA6blends on flame retardancy were investigated. The TEMimages showed that OMMT which had reacted with compatibilizer SMA distributed in the interface of the blends. Oxygen index and vertical burning test showed that thedistribution of OMMT has no significant effects on flame-retardant properties of theblends with PA6as the dispersed phase. However, in blends with a continuous PA6phase, the flame retardancy of blends with OMMT dispersed at the interface was betterthan that of blends with OMMT dispersed in PA6phase. An investigation of TGanalysis revealed that the thermal stability of blends with OMMT dispersed at theinterface showed obvious change with blends in which OMMT dispersed in PA6phase.Scanning electron microscopy (SEM) characterization showed that the dispersion ofOMMT at the interface had the benefit of forming a compact residue char, whichaugmented the flame retardancy. A completely loose residue char observed in theblends with continuous PA6phase in which contained OMMT platelets should beresponsible for the deterioration of flame retardant properties. Energy dispersivespectrometry (EDS) analysis revealed that the reassembling of the OMMT platelets onthe surface of intumescent char caused the formation of loose residue char. On thecontrary, the dispersion of OMMT platelets on whole intumescent char was morefavorable to the improvement of flame retardancy.