Preparation Of Highly Efficient Intumescent Flame Retardants And Their Application In Flame-retardant Polypropylene

Polypropylene（PP）is widely used in many fields,such as electronic equipment,food packaging,and manufacturing due to its chemical resistance,facile processing,good electrical insulation and high transparency.However,PP is extermely flammable,with a large amount of melt dripping and generation of toxic gas during combustion,limiting its application in specific fields.Therefore,it is essential to carry out the flame retardant modification.At present,intumescent flame retardants（IFR）are highly effective and used widely for PP.In this thesis,piperazine phosphate salt char-forming agent and mono-component IFR were synthesized by ion exchange reaction and applied to flame retardant modification of PP.The main research contents and results are as follows:（1）The piperazine phosphate salt char-forming agent ATPIP was synthesized through the ion exchange reaction,using amino trimethylene phosphoric acid（ATMP）and piperazine as raw materials.A mono-component flame retardant was prepared by self-assembly reactions between 1-（2-aminoethyl）piperazine and p-amino benzenesulfonic acid,followed by an ion exchange with APP.The chemical structure and thermal stability of the ATPIP and MAPP were characterized by Fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance（¹H NMR）,X-ray diffraction（XRD）,X-ray spectroscopy（XPS）,scanning electron microscope（SEM）and thermogravimetric analysis（TGA）.（2）The PP/MAPP/ATPIP blends were prepared on the internal mixer by melt blending method.The performances of the blends were systematically analyzed,the flame retardant effect of different proportions and dosages of ATPIP and MAPP on the PP was investigated.The possible IFR mechanism was revealed.The results of research showed that the addition of MAPP and ATPIP in an appropriate proportion could significantly improve the flame retardancy of the PP matrix.In case of the incorporation of 25 wt.%（MAPP/ATPIP）_3/1,the blends passed UL-94 V-0testing.The results of cone calorimetry test（CCT）showed that the addition of MAPP and ATPIP exhibited excellent smoke suppression effects and reduced the risk of fire.The TGA results showed that the addition of flame retardant promoted the formation of carbon and reduced the thermal degradation rate of the blends.MAPP and ATPIP exhibited a synergistic IFR mechanism.On the one hand,it generated incombustible gas and phosphate oxygen radicals to dilute the concentration of combustible gas and terminated the free radical chain combustion reaction.On the other hand,it formed an expanded and dense carbon layer to prevent further burning of the substrate.The mechanical test showed that the addition of ATPIP led to the phenomenon of stress whitening,which dissipated the applied energy during the tensile or impact test,thereby improving the mechanical properties of the blends.（3）The PP/APP and PP/MAPP flame retardant blends were prepared on the internal mixer by melt blending.The flame retardant efficiency of APP and MAPP were compared,and the flame retardant effect of different dosages of APP and MAPP on the PP was explored.The possible flame retardant mechanism was revealed.MAPP showed more effective flame retardant properties than APP.When 22.5 wt.%MAPP was added,the blends passed UL-94 V-0 rating.The results of CCT indicated that adding MAPP could significantly improve the smoke suppression effect and fire safety of the blends.TGA results showed that the addition of MAPP advanced the initial decomposition temperature of the blends,reduced the maximum decomposition rate,and increased the system’s carbon residue rate.MAPP exhibited a mono-component IFR mechanism.The results of mechanical test showed that MAPP particles were evenly embedded in the PP matrix,having little effect on the mechanical properties of the blend.