Halogen-free Intumescent Flame Retardant Polypropylene

The process for synthesis of intumescent flame retardant NPM was analyzed in this paper. The yield of NPM could reach 85% in lab. Molecular structure of NPM was further confirmed by Elementary Analysis and FT-IR, and the mode of thermal degradation of NPM was evaluated by thermal analysis (DTA, TGA). The result showed that NPM had high thermal stability and char yield. It started melting and degrading at about 300℃, and the char yield could reach 13.4% at 600℃.Properties of PP/NPM systems were studied by using Limiting oxygen index (LOI), horizontal burning (HB) test, thermogravimetric analysis (TGA), scanning electronic micrograph (SEM), infrared spectra (IR), etc. The result showed that NPM could improve the thermo-stability of PP/NPM system, and the intumescent char was obtained on the surface of burned sample. LOI reached 26.8% when the NPM was added to 30phr, and the char yield also reached 8.30% at 600℃.Nano-CdS, nano-BaWO₄, nano-Mn_0.4Zn_0.6Fe₂O₄ were used into the PP/NPM (100/30) system as flame retardant synergistic agents. The synergistic effect of these nano-compounds was evaluated by using LOI, HB, TG, TEM, IR, etc. The result showed that each synergist influenced the degradation process of flame retardant PP, catalyzed the process of char forming. And the structure of char was further intumesced when using the different synergistic agents. The LOI and the yield of char could reach 30.2% and 13.86% respectively, when nano-CdS was added to l.Ophr. Nano-BaWO₄ showed an effective synergism in the intumescent flame retardanct system, the LOI could reach 29.8% when the concentration of nano-BaWO4 was 1.5phr. Nano-Mn_0.4Zn_0.6Fe₂O₄ also has a synergistic effect in the PP/NPM system, and its optimal content was l.Ophr.In this paper, the rheologic and mechanical properties of flame retardant PP systems were also measured by capillary rheometer, tensile strength, elongation at break and impact strength. The result showed NPM enhanced the shear viscosity of PP/NPM systems and impact strength, but the tensile strength and elongation at break was decreased. It is also showed the synergistic agents had little influence on rheologic and mechanical properties of the systems.