Synthesis Of Triazine-based Charring Agents And Their Synergistic Effects With Ammonium Polyphosphate In Flame Retardant Polypropylene

Due to its high water solubility, poor thermal stability and easily migration ofpentaerythritol (PER) which was commonly used as charring agent in intumscent flameretardant (IFR), the water resistance of flame retardant PP are deteriorated and the materialare foamed badly. In order to solve those problems, two novel triazine-based charring agentsnamely ETCA and SiTCA were designed and synthesized by using cyanuric chloride,diethanolamine, γ-aminopropyl triethoxysilane and so on. Ammonium polyphosphate (APP)and ETCA (or SiTCA) were used for the preparation of flame etardant PP. The effects ofAPP/ETCA (or APP/SiTCA) on the flame retardancy, thermal stability and water resistance ofPP were studied, and a comparative study of them with APP/PER was conducted.Furthermore, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy(FT-IR), thermogravimetric analyzer-Fourier transform infrared spectrometry (TG-FTIR) andso on were employed to characterize the flame retardant mechanism of APP/ETCA. The mainresearch contents and results are listed as following:First, flame retardant PP was prepared by using APP/PER as flame retardant. It wasfound that APP/PER was effective in improving the flame ratardancy of PP, bud the smokesuppression, thermal stability, mecahinical property, and water resistace properties of thematerial needed to be further improved. When the mass ratio of APP/PER was2:1, thecontent was25wt%, the LOI of flame reatardnat PP was31.0%and could meet UL-94V-0rating. The peak of heat release rate (pHRR), average of heat release rate (av-HRR) and peakof smoke produce rate (pSPR) were reduced obviously. However the total smoke production(TSP) was increased by21.7%; the The initial decomposition temperature (T_i) is decreased by8.7℃; the tensile strength and impact strength were decreased by28.9%and6.7%. Afterwater resistance test, the LOI of flame retardant PP decreased obvisiously and couldn’t meetany UL-94rating.Second, a novel triazine-based charring agent namely ETCA with excellent thermalstability, outstanding char-forming ability and low water solubility was designed andsynthesized by using cyanuric chloride, diethanolamine, ethylenediamine, etc.. And thehalogen-free flame retardant PP was prepared by using APP/ETCA as flame retardant. It was found that APP/ETCA had an excellent flame retardant and smoke suppression effect on PP,and the mechanical properties, thermal stability and water resistance of flame retardant ppwere imporved remarkably while compared with PP/APP/PER blends. When the mass ratio ofAPP/ETCA was2:1, the content was20wt%, the LOI of flame retardant PP was30.5%andcould meet UL-94V-0rating. The cone calorimetry test (CCT) results showed that the pHRR,total heat release (THR), pSPR, TSP and average of mass lose rate (av-MLR) ofPP/APP/ETCA were reduced by56.1%、30.2%、64.6%、57.5%and59.6%, respectively, whencompared with PP/APP/PER blends. After water resistance test, the LOI of flame retardant PPdecreased, but still could meet UL-94V-0rating. The TGA, FT-IR,3D TG-FTIR resultsimplied that the fame retardant mechanism of APP/ETCA was in the condensed phase ratherthan in the gas phase. When the temperature was higher than300℃, APP and ETCAdecomposed successively, than the system undergone esterification, charring rceaction andfoaming, finally, the system formed intumescent char which protect the resin from heat andoxygen.Third, silicon-containing triazine-based charring agent (SiTCA) with excellent thermalstability, outstanding char-forming ability and low water solubility was synthesized by usingcyanuric chloride, diethanolamine, γ-aminopropyl triethoxysilane, etc., and the halogen-freeflame retardant PP was prepared by using APP and SiTCA as flame retardant. It was foundthat SiTCA showed good synergistic effects with APP, and the flame retardant PP showedexcellent comprehensive performance. When the mass ratio of APP/SiTCA was3:1, thecontent was20wt%, the LOI of flame retardant PP was31.5%and could meet UL-94V-0rating. CCT results showed that the pHRR, THR, pSPR, TSP and av-MLR of PP/APP/SiTCAwere reduced dramatically when compared with PP/APP/PER blends. TG results showed thatthe char residue at750℃of PP/APP/SiTCA was11.5%which was increased by180.5%when compared with PP/APP/ETCA blends. After water resistance test, the LOI of flameretardant PP decreased, but still could meet UL-94V-0rating.