Study On Surface Modification Of Magnesium Hydroxide And Its Application In Polymers

Magnesium hydroxide?Mg?OH?₂?is an important additive inorganic flame retardant,which has the advantages of non-toxic,smokeless,non-corrosive,high decomposition temperature,can effectively promote the substrate into carbon and low cost.It is one of the inorganic flame retardants commonly used in modern society.However,Mg?OH?₂ has strong hydrophilicity and high surface polarity,which leads it have poor compatibility with non-polar polymer materials.The direct addition of Mg?OH?₂ will result in the uneven dispersion of Mg?OH?₂ in the polymer material,which will seriously affect the processing and mechanical properties of the composite material.Surface modification of Mg?OH?₂ can improve the surface properties of Mg?OH?₂ and enhance the compatibility with matrix materials.This paper reviews the research progress of traditional flame retardants and Mg?OH?₂ flame retardants in recent years,and discusses the modified Mg?OH?₂ through single modifier dodecyl dihydrogen phosphate?DDP?and composite modifier DDP/ silane coupling agent?KH550?.Tests such as activation index and water contact angle investigate the effects of modifier ratio,modifier dosage,reaction time and reaction temperature on the modification effect of Mg?OH?₂,and a relatively better modification process is obtained.And using XRD,SEM,FT-IR,TG-DSC,XPS,etc.to characterize the Mg?OH?₂ before and after modification,draw the conclusions: the hydrophobicity of the modified Mg?OH?₂ is enhanced,and the the crystal structure has not changed.The thermal stability is improved,and the modifier and Mg?OH?₂ are present in a bonded form.In addition,Mg?OH?₂ before and after modification is added to epoxy resin?EP?and polypropylene?PP?,and the mechanical properties,thermal stability and flame retardancy of the composite are tested,and the following conclusions are obtained:?1?The addition of modified Mg?OH?₂ to EP makes the tensile strength and elongation at break of the composite higher than that of the unmodified EP/Mg?OH?₂ composite;When the added amount of Mg?OH?₂ is 40%,the LOI value of the composite with unmodified Mg?OH?₂ is 28.47%.The composite of Mg?OH?₂ modified by KH550,DDP,DDP/KH550,the LOI values of the materials are 29.29%,28.96%,and 29.37%,indicating that the flame retardancy of the modified composite is improved,at the same time the thermal stability of the modified composite is also improved,and the amount of residual carbon is increased.?2?When the Mg?OH?₂ before and after modification is separately mixed with the PP matrix,the torque of PP mixed with modified Mg?OH?₂ is smaller than that of the unmodified composite material,indicating that after the modification compatibility with PP and Mg?OH?₂ is improved and processing rheology is improved.Mg?OH?₂ modified by DDP/KH550 has the best processing rheology in PP;With the increase of the amount of Mg?OH?₂,the mechanical properties of the composites gradually decrease,and the addition of modified Mg?OH?₂ can reduce the deterioration of the mechanical properties of the PP matrix;When the addition amount of Mg?OH?₂ is 50%,the LOI value of the composite with unmodified Mg?OH?₂ is 25.97%,and the composite of Mg?OH?₂ modified by KH550,DDP,DDP/KH550,the LOI values of the materials are 26.81%,27.20%,and 27.53%,indicating that the flame retardancy of the modified composites is improved,and the thermal stability of the modified Mg?OH?₂ composites is also improved.