Synthesis Of Microcapsule Flame Retardant Containing Magnesium Hydroxide And Its Application In EVA

Owing to its flame-retarding,smoke-suppressing and filling functions as well as no secondary pollution,good thermal stability and low price,magnesium hydroxide(MH)is widely used to flame retard polymer materials and it is well-recognized to be an environmental-friendly halogen-free flame retardant.However,the MH prepared by the conventional method has such disadvantages as strong polarity and hydrophilicity,poor compatibility with polymer matrix,easy agglomeration,low flame-retardant efficiency,and large addition amount.Thus,the modification of MH is an important means to improve its flame-retardant efficiency.First of all,this thesis uses 4,4’-diphenylmethane diisocyanate(MDI)and melamine(MEL)as raw materials,MH and the mixture of MH and red phosphorus(MH&RP)as core materials,and prepares MHcontaining microcapsule flame retardant through in-situ polymerization.The structure and property of the microcapsule flame retardant were characterized by various means.Then,EVA/MMH and EVA/M[MH&RP] composites were prepared with EVA resin as the matrix.The flame retardancy and flame retardant mechanism of the composites were investigated.Moreover,carbon nanotube(CNT)and glass fiber(GF)were incorporated into the EVA/M[MH&RP] composite and their effects on the flame retardancy of this composite were studied respectively.The main content and conclusions of this thesis are as follows.1.Using MDI and MEL as raw materials and MH and(MH&RP)as core materials,microcapsulated magnesium hydroxide(MMH)and magnesium hydroxide and red phosphorus co-microcapsule(M[MH&RP])were prepared by in-situ polymerization respectively.The structure and property of the microcapsules were characterized by SEM,FTIR,EDS,TGA and water solubility tests.The results indicate that microcapsules with polyurea as shell and MH or [MH&RP] as core can be successfully synthesized by in-situ polymerization.After microencapsulation modification,the thermal stability and dispersibility of the flame retardant are improved and the hydrophilicity of the flame retardant is decreased.2.A series of EVA/MMH and EVA/M[MH&RP] composites were prepared by melt blending with EVA resin as the matrix.The flame retardancy and flame-retardant mechanism of the composites were investigated by vertical burning test,limiting oxygen index(LOI),SEM,cone calorimeter test and acid treatment methods.The results show that microencapsulation can significantly improve the flame-retardant efficiency of the flame retardant,reduce the amount of flame retardant,and can promote the formation of a more stable char layer during combustion.The obtained composites have excellent acid resistance and good flame retardancy.At the same time,the one-step method can reduce the number of times to add the flame retardant and simplify the modification process,which is beneficial to the flame-retardant synergistic effect between MH and RP.3.Different amounts of CNT and GF were introduced into the EVA/M[MH&RP] composite through melt blending respectively and the flame retardancy and flameretardant mechanism of the composites were investigated by vertical burning test,LOI and cone calorimetry tests.It has been shown that there is good synergism between CNT and M[MH&RP] co-microcapsuleson on the flame retardancy of EVA.The addition of a small amount of CNT can significantly reduce the heat and smoke release of the EVA/M[MH&RP] composites and improve residue quantity and fire performance index,exhibiting good flame retardant smoke suppression performance.When the mass ratio of EVA/M[MH&RP]/CNT is 65/32/3,the LOI value of this composite is 30.1% and the composite has good overall performance and low cost.The introduction of GF can maintain the vertical burning rating of EVA/M[MH&RP] composites at V-0 level without the “wick effect”.At the same time,both heat and smoke release of the EVA/M[MH&RP] composite are reduced observably.The burning time of the composite is prolonged and both the residue amount and the fire performance index of the composite are improved considerably.The EVA/M[MH&RP]/GF composite exhibits excellent flame retardancy and smoke suppression.In addition,the tensile strength of the composite is increased after introducing GF,which has played a certain reinforcing effect.When the amount of GF is 10 wt%,the composite material has the best overall performance.