Controlling Distribution Of Intumescent Flame Retardants In Polymer Blends And Their Flame Retardancy

Synergistic flame retardant effects between intumescent flame retardant(IFR)and organic montmorillonite(OMMT)has been employed for improving the efficiency of halogen-free flame retardant in polymers.However,the localization of flame retardant and OMMT in polymer blends was different from that in polymers and the effect of localization on flame-retardation synergism has been ignored.Therefore,this application used ammonium polyphosphate(APP)and pentaerythritol(PER)as intumescent flame retardant system and OMMT as synergistic additive to retard the flame of polymer blends of linear low density polyethylene and nylon 6(LLDPE/PA6).A new approach should be employed for controlling the localization of IFR and OMMT in polymer blends,researching on the flame retardancy of LLDPE/PA6 with the distribution of APP,PER and OMMT.Firstly,the influence of proportion and content of APP and PER in intumescent flame retardant system about the properties of flame retardant blends was studied,discovering that it was good for sample to pass the vertical flammability UL-94 test,achieving grade V-0 and to reach 29.70% by limiting oxygen index(LOI),when the common content of APP and PER was 20 wt%,the proportion of APP and PER was 4:1.The results showed that the charred layers after burning displayed obvious distinction in the proportion and content of IFR(APP/PER)by scanning electron microscope(SEM)and the samples of 25wt% and 20 wt% were the best continuous compact charred layers when APP:PER was4:1.APP and PER were spontaneously distributed in the strong polarity phase of PA6 by fourier infrared spectrum(FTIR).Secondly,because of the different melting temperature of the substrate materials,different distribution of flame retardant composite materials by temperature controlling were obtained and their performance was researched.The different distribution of materials were processed when the common content of APP and PER was 20 wt%,APP: PER was 4:1.The results showed that it was not obvious impact on the material's thermal stability and the flame retardancy of materials by thermo-gravimetric analysis(TG)and SEM tests.Then,the additions of OMMT with difference content of 5 wt%,3 wt%,1 wt% to intumescent flame retardant system were processed.The flame retarding effects of IFR and OMMT on the flame retardancy were investigated.The flame retardancy and the charred layers after burning were analyzed by LOI,UL-94,SEM and TG tests.The results showed that,LLDPE/PA6/APP/PER/OMMT system with 1 wt% OMMT displayed excellent flame retardancy comparing to LLDPE/PA6/APP/PER system,besides,appropriate quantity of OMMT on intumescent flame retardant was synergistic effect.OMMT also was spontaneously distributed in PA6 phase by transmission electron microscope(TEM).Finally,the different kinds of distribution state by temperature controlling of APP,PER and 3 wt% OMMT in LLDPE/PA6/APP/PER/OMMT system were respectively processed.The results showed that different distribution has little effect on the thermal degradation process of materials by TG test,the flame retardancy and the charred layers were bad comparing to the other distribution by LOI,UL94 and SEM tests when OMMT was distributed in PA6 phase and one of APP,PER or both them was distributed in PA6 phase,the reason that reduced the flame retardant performance of materials was that OMMT increased viscosity of PA6 and inhibited the process of the charred layers.