Relationships Between Rheological Behaviors And Mechanical Properties Of Polyethylene Nanocomposites With Different Dimensions Carbon Fillers

Blending polymers with nano-fillers is an effective way to improve their properties and enlarge applications.Polymer nanocomposites have become one of popular polymer research fields.The addition of carbon fillers can not only toughen and reinforce polymers,but also improve significantly the resistivity of the matrix.However,the properties of polymer nanocomposites are seriously affected by the type,dimension,concentration,surface modification methods of fillers and the types,molecular weight of polymer matrix.Generally,the optimal components of polymer nanocomposites are determined through a large number of orthogonal experiments.Therefore,it is important topic how to find an easy way to determine quickly the optimal polymer nanocomposites.In this project,HDPE/CB nanocomposite,LLDPE/MWCNT nanocomposite and HDPE/MWCNT nanocomposite were prepared by melt blending.The effects of the dimension and concentration of the filler,the type and concentration of the compatibilizer on the rheological properties,mechanical properties,electrical properties and morphologies of the polyethylene nanocomposites had been investigated.The correlations between rheological characteristics and mechanical properties of polyethylene nanocomposites were established by exploring the corresponding relationship between the characteristic viscoelastic parameters and the key mechanical parameters of the polyethylene nanocomposites.Thus,the optimal components of polyethylene nanocomposites could be quickly determined by rheology test with short periods and a few samples.The results can be summarized as follows:(1)The gel points of HDPE/CB nanocomposites,HDPE/CB nanocomposites with5%HDPE-g-MAH,and HDPE/CB nanocomposites with 10%HDPE-g-MAH compatibilizer are 10.8,9.6 and 9.4 wt%,respectively.The notched izod impact strength of HDPE/CB nanocomposite corresponding to the gel point is about half that of pure HDPE,and the volume resistivity is reduced by about 10 orders of magnitude.The gel points are located in the conductive percolation zone.There is no correlation between the rheological characterisics and mechanical properties of HDPE nanocomposites filled with zero-dimensional CB.(2)The gel points of LLDPE/MWCNT nanocomposites,LLDPE/MWCNT nanocomposites with 5%HDPE-g-MAH compatibilizer are 1.83 and 1.97 wt%,respectively.The notched izod impact strength of the nanocomposites corresponding to the gel points reach the maximum values of 48.03 kJ/m~2 and 47.41 kJ/m~2,and the volume resistivity are 8 and 5 orders of magnitude lower than that of LLDPE,respectively.The gel point is located in the conductive percolation zone.There is a corresponding relationships between the gel points and super toughness points.(3)The gel points of HDPE/MWCNT nanocomposite,HDPE/LLDPE-g-MAH/MWCNT nanocomposite and HDPE/HDPE-g-MAH/MWCNT nanocomposite are4.23,1.95,and 2.75 wt%.At the gel points,the notched izod impact strength of HDPE/LLDPE-g-MAH/MWCNT and HDPE/HDPE-g-MAH/MWCNT composites are 65.45 kJ/m~2and 65.05 kJ/m~2,which is about 3 times as high as that of the pure HDPE,and the volume resistivity decrease by 6 orders of magnitude.The gel points are located in the conductive percolation zone.The gel points of HDPE/LLDPE-g-MAH/MWCNT and HDPE/HDPE-g-MAH/MWCNT nanocomposites have obvious corresponding relationships with the super toughness points.(4)When the concentration of HDPE-g-MAH is 1,3,5 and 7 wt%,the gel points of HDPE/HDPE-g-MAH/MWCNT nanocomposites are 2.45,2.20,2.75 and 2.70wt%,respectively.The notched izod impact strength of the nanocomposites at gel points are 57.49 kJ/m~2,59.08 kJ/m~2,65.05 kJ/m~2 and 44.17 kJ/m~2,which are significantly higher than that of pure HDPE,the volume resistivity are also significantly reduced.Except for HDPE/MWCNT nanocomposites with 7 wt%HDPE-g-MAH,there is corresponding relationships between the gel points and super toughness points of the other three nanocomposites.(5)The nanocomposites corresponding to the gel points exhibit special network structure,and the addition of compatibilizer can induce the gel network more perfect.The superelasticity of the gel point corresponding to the composite material stems from the pull-out,fracture,elastic deformation of the MWCNT,and the destruction of the special network structure and large area tear of the matrix.