| Polypropylene(PP)has been widely used in wire,cable,transportation,automobile and electronic appliances due to its excellent mechanical and chemical corrosion resistance.However,the flammability of PP matrix limits its application.Intumescent flame retardant(IFR)can effectively improve the flame retardancy of PP.But most of IFR system are multi-components and the uniform dispersion between components is difficult,which declines the synergistic effcts between each other.Moreover,the components of IFR are strong polarity and poor water resistance.The mono-component IFR including all the gredients can exert much better synergistic effcet.Therefore,the preparing of water-resistant mono-component IFR has important scientific significance and practical application value.In this thesis,a novel flame retardant additive poly(dimethylol melamine piperazine pyrophosphate)defined as PDMPP was designed and synthesized from formaldehyde,melamine and piperazine pyrophosphate.Its chemical structure was characterized and confirmed by Fourier transform infrared spectroscopy,13C and 31P solid-state nuclear magnetic resonance and elemental analysis tests.The solubility of PDMPP in water at 70? was 0.26 g/100g water,and it indicated that the flame retardant possessed good water resistance.The results of thennogravimetric analysis(TGA)tests revealed that the initial thermal decomposition temperature of PDMPP was 255? and the residual char mass at 700? was 29.6%.Consequently,the obtained flame retardant additive presented good thermal stability and charring capability.The synthesized PDMPP was incorporated into PP matrix and prepared flame retardant PP(FR-PP)composites.The results revealed that the samples successfully passed UL-94 V-0 rating without droplets during vertical burning tests,and the limiting oxygen index(LOI)value reached 26.7%when the loading amount of PDMPP was 23 wt%.After the FR-PP was immersed into water at 70? for 168 h and dried,the sheets still passed UL-94 V-0 rating with the LOI value of 26.3%.Meanwhile,the weight loss rate percentage of the samples was 0.67%.It indicated that the flame retardant PP composites maintained excellent flame retardant properties,and only small amount of PDMPP was extracted during water resistance test.Compared with pure PP materials,the heat release rate(HRR),smoke release rate(SPR),and carbon monoxide production(COP)of flame retardant PP composites before and after water resistance tests were obviously reduced.The water resistance test slightly declined the flame retardant performance of materials.Raman spectrum tests revealed that the formed char layer presented a certain degree of graphitization.The char layer with high quality exerted a good barrier effect during combustion process,and then effectively enhanced the flame retardant performance of the PP composites.PMPPP mixed with ammonium polyphosphate(APP)and incorporated into PP matrix to preparing the flame retardant PP composites.The results indicated that the PP/PDMPP/APP composites passed UL-94 V-0 grade and the LOI value reached 26.9%when the total loading amount of flame retardant was 21 wt%with the mass ratio of PMPPP/APP was 5:1.It indicated that APP and PMPPP presented good synergistic flame retardant effect for PP matrix.The CONE test showed that the heat release rate and total heat release of PP/PDMPP/APP was lower than that of PP/PDMPP composites,and more amount of char residue was generated after combustion.The analysis of the morphology and composition of the residual char layer revealed that the introduction of APP stimulated the formation of more sufficient,thick and compact char layer during combustion process,which exerted much better isolation effect and further improved the flame retardant efficiency of PP composites. |
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