Study On Preparation And Properties Of Magnesium Hydroxide/Zinc Oxide Whisker/Low Density Polyethylene Composites

Low density polyethylene（LDPE）possesses the advantages of low price,non-toxicity,low temperature resistance and easy processing,and has been widely used in various fields,such as agricultural film,packaging products and foam products.However,LDPE is composed of hydrocarbon elements,so it burns easily,accumulates electric charges during friction process and limits its application in some special cases.In this thesis,maleic anhydride grafted polyethylene（MAH-g-LDPE）was first synthesized,and then the composites and foam materials were prepared by low density polyethylene（LDPE）as matrix,MAH-g-LDPE and titanate 201 as surface treating agents,magnesium hydroxide（Mg（OH）₂）as Flame retardant and zinc oxide whisker（ZnO_w）as antistatic agent.The performances of the composites,such as mechanical properties,thermal stability,flame retardancy and antistatic properties were researched.The resultswere as follows:（1）MAH-g-LDPE was synthesized by melt-grafting reaction with t-butyl peroxybenzoate（TBPB）as initiator and maleic anhydride（MAH）as monomer.The product structure was characterized by Fourier infrared spectrum（FTIR）,and the influence of the dosage of the initiator and monomer on the grafting ratio and gel content of the products were studied.When TBPB and MAH amount was 0.2%and2.5%respectively,the graft ratio was highest,which was 2.30%and gel content was3.14%.（2）The blending process and the amount of the modifiers were optimized by LDPE as the matrix and Mg（OH）₂ as the inorganic filler.Process 4,which the temperatureofI^Vzonearesuccessivelyasfollowing:150°C,155°C,160°C,165°C,160°C,and the extrusion speed,which was 10r/min,were chosen.Moreover,the better result was obtained when the relative ratio and dosage of titanate 201 and MAH-g-LDPE as a combined surface treatment agents was 50:50 and5.00%respectively.（3）The flame retardant Mg（OH）₂/LDPE composites were prepared by Mg（OH）₂as fire retardant and titanate 201 and MAH-g-LDPE as surface modifier through melt blending method.The influence of on the mechanical properties,thermal stability,microstructure and flame retardancy of the composites were researched.When the addition amount of Mg（OH）₂ is more than 15%,the melt-droping phenomenon disappeared and oxygen demand increased.When Mg（OH）₂ dosage was 15%,the horizontal combustion rate was 34.09mm/min and limiting oxygen index（LOI）was23.7%,so the composites had flame-retardant properties and reached level HB40according to horizontal combustion method（GB/T 2408-2008）.（4）The flame retardant and antistatic Mg（OH）₂/ZnO_w/LDPE composites were prepared by ZnO_w as antistatic agent,15%Mg（OH）₂ as fire retardant through melt blending method.The influence of ZnO_w dosage on the mechanical properties,thermal stability,microstructure,flame retardancy and antistatic property of the composites were analyzed.When the addition amount of ZnO_w was more than 5.0%,the volume resistivity of the composites decreased to 10¹²Ω·m and reached the antistatic performance.At the same time,the horizontal burning result also reached level HB40 and had flame retardant properties.When ZnO_w dosage was 7.5%,the volume resistivity was 1×10¹¹Ω·m,the horizontal combustion rate was 35.57mm/min and LOI was 24.7%.（5）The foam materials were prepared by the azodicarbonamide（AC）as foaming agent and 15%Mg（OH）₂/7.5%ZnO_w/LDPE composite as matrix.The foaming process was optimized and the influence of foaming agent dosage on the apparent density,mechanical properties,microstructure,flame retardancy and antistatic property of the foam materials were explored.When the foaming temperature and time was 200℃and 60min respectively,the foaming effect was better.Howerver,the results showed that the foam material prepared could not meet the requirements of flame retardant and antistatic property because of the microcellular structure.