Study On The Halogen-free Flame Retarded Nylon66/OMMT/SiO₂ Nanocomposite

In this research topic, organic montmorillonite(OMMT) and surface modified SiO₂ were dispersed into nylon66 resin by the method of melt-blending, and the nanocomposite was got; ammonium polyphosphate(APP) and melamine(MA) as intumescent flame retardant(IFR) blending with OMMT and SiO₂ prepared intumescent flame-retarded nylon66 nanocomposite; zinc oxide(ZnO) was used as flame-retarded synergist, Synergistic flame-retarded nanocomposite was produced. In the experiment, the influence of materials components ratio alteration on nylon66 properties was discussed, the contrastive study of mechanical properties and burning behaviour of different formulation was analyzed. In addition, the mechanical properties and burning behaviour of intumescent flame-retarded nylon66 nanocomposite were studied, the OMMT and SiO₂ nanoparticles can reinforce the nylon66/IFR materials and have Synergistic effect with IFR. The Synergistic effect of ZnO was studied by limiting oxygen index(LOI), vertical combustion testing and infrared spectrum(IR), eventually gained UL94V-0 flame retardant nylon66 nanocomposite.The results of nylon66 nanocomposite indicated when the content of OMMT and SiO₂ were 2.0% and 1.5%, the tensile strength was higher 8.84% than that of pure nylon66, the impact strength was higher 14.49%; the scanning electron microscope (SEM) of the fracture accounted that the materials emerged plastic deformation and consumed much energy. In addition, the glass transition temperature was higher 59.6°C than pure nylon66, the char residue ratio was higher 5.95 than pure nylon66. OMMT and SiO₂ improved the thermal stability of nylon66.The testing results of flame-retarded materials showed when the content of intumescent flame retardant increased, the LOI was rising, but the mechanical properties decreased largely. OMMT and SiO₂ could improved the mechanical properties and have Synergistic fire-retarded effect, When the content of MA and APP was 20%, the tensile strength of containing OMMT (2%) materials was higher 5.13% and LOI was higher 2.13% than that was non-OMMT; SiO₂ has better heat-durability, the tensile strength of appending SiO₂(1.5%) and OMMT(2.0%) was higher 8.89% than without it, the impact strength higher 10.21%, the LOI higher 4.61% and the materials arrived at UL94 V-0 level.When the content of ZnO was 2.0%, the LOI was higher 11.19% than intumescent flame-retarded base materials, achieved optimal Synergistic flame retarded properties, and the influence of ZnO content on mechanical properties was quite small. the SEM observed indication that suitable ZnO Synergistic agents might accelerate the esterification and charring progress of IFR system, and changed the microscopic structure of final char layer, which made char layer condensation closely each other and minimize pores.