Synthesis Of Organic-inorganic Hybrid Char-forming Agent And Its Flame-retardant Application In Polypropylene Composites

Metallic oxides can catalyse more stable char forming of intumescent flame retardant systems as synergistic agents and are widely used in polypropylene.However,the flame retardant efficiency of metallic oxides is greatly affected because of the very low addition amounts of the oxides and the poor compatibility between metallic oxides and polymer matrix.Therefore,the organo-modification,especially the organic modifiers with high flame retardancy of metallic oxides is a promising way.The metal oxides were organic modified by using triazine derivatives in this paper,several kinds of novel organic-inorganic hybrid char-forming agent(SCTCFA-MO,M=Zn,La,Ti,Ce)were synthesized and characterized by Fourier transform infrared spectrometry(FT-IR)and solid state nuclear magnetic resonance(SSNMR).They were respectively chosen and blended with ammonium polyphosphate(APP)to prepare intumescent flame retardant polypropylene(PP)composites.The flame retardancy and thermal degradation behaviour of PP composites were investigated by the means of limited oxygen index(LOI),vertical burning test(UL-94),cone calorimeter test and thermogravimetric analysis(TGA).The mechanism of organic/metal oxides hybrid flame retardant PP composites was studied,and this is the theoretical basis for the optimization of the novel efficient organic/metal oxides hybrid flame retardant system in particular conditions.This dissertation is composed of three parts:(1)A novel organic-inorganic hybrid char-forming agent SCTCFA-ZnO was synthesized with transition metal zinc oxide as the research object.The flame retardancy and mechanical properties of PP/APP/SCTCFA-ZnO composites were investigated with 25 wt.%the total loading of APP/SCTCFA-ZnO.Results showed that SCTCFA-ZnO had the best flame retardant performance in PP composites when ZnO has 14 wt%in the hybrid compound.The results from LOI and UL-94 indicated that the optimum mass ratio of APP/SCTCFA-ZnO was 2:1 when PP/APP/SCTCFA-ZnO composites showed the best flame retardant effect,and the LOI of composites was 31.1,pass UL-94 V-0 rating.The Cone calorimeter test results showed that the total thermal release(THR)and total smoke release(SPR)of PP/APP/SCTCFA-ZnO composites were significantly decreased.It was found that the flame retardant performance and mechanical properties of PP/APP/SCTCFA-ZnO were better than that of PP/APP/SCTCFA/ZnO.The action mechanism of nano-ZnO may be catalytic the crosslinking reaction of APP deamination and dehydration,reducing the volatilization of phosphorus and oxygen compounds in combustion.Therefore,more P,O,N and other flame retardant elements remain in the condensed phase.(2)A novel organic-inorganic hybrid char-forming agent SCTCFA-La2O3 was synthesized with rare earth metal lanthanum oxide as the research object.The flame retardancy of PP/APP/SCTCFA-La2O3 composites were investigated with 30 wt.%the total loading of APP/SCTCFA-La2O3.The results from LOI and UL-94 indicated that the optimum mass ratio of APP/SCTCFA-La2O3 was 3:1 when PP/APP/SCTCFA-La2O3 composites showed the best flame retardant effect,and the LOI of composites was 31.5,pass UL-94 V-0 rating.The Cone calorimeter test results revealed that the synergistic flame retardant and smoke suppression effect between APP and SCTCFA-La2O3.The flame retardant pattern and mechanism of PP composites were studied by TGA,scanning electron microscopy(SEM),laser Raman spectroscopy analysis(LRS),FT-IR and X-ray photoelectron spectroscopy(XPS).The synergistic effect between APP and SCTCFA-La2O3 could change the thermal degradation behaviour of PP and promoted more P-O-C and P-O-Si crosslinking structure in the char residue.The mechanism of nano-La2O3 may be the catalytic formation of crosslinked polyphosphoric acid chain structure and the adsorption of ammonia,increase the combustion stability of char layer.(3)The other two organic-inorganic hybrid char-forming agent SCTCFA-TiO2 and SCTCFA-CeO2 were synthesized.The flame retardancy of PP/APP/SCTCFA-MO,M=Zn,La,Ti,Ce composites was investigated.The results showed that SCTCFA-ZnO had the best flame retardant effect in PP composites from LOI and UL-94 test.SCTCFA-La2O3 showed the best smoke suppression effect in cone calorimeter test.