Study On High Performance Polyethylene Nanocomposites

In this paper, high density polyethylene (HDPE) was modified by montmorillonite (MMT) which modified in different methods to obtain a high-density polyethylene nano composite by using a twin-screw melt extrusion.Meanwhile,to obtain a high strength in the nano composite and compensating for the loss of toughness, one kind of new thermoplastic polyolefin elastomer (POE) was added for its toughness.Thermoplastic elastomer which grafted with maleic anhydride (POE-g-MAH) was the final selected as compatibilizer to enhance interactions between inorganic nano-fillers and the polymer. At last,high density ethylene nanocomposites holding high performance was created successfully.The experiment results was analyzed by using mechanical performance tester, oxygen index analyzer, differential scanning calorimeter, thermal Gravity Analysis, scanning electronic microscopy, transmission electron microscopy, X-Ray powder diffraction and so on.It helped know about mechanical properties, flame retardancy, crystallinity, thermal stability, internal structure, nano-montmorillonite interlayer spacing and other aspects of performance clearly.The results of HDPE/POE nanocomposite show that:when 5 phr MMT added, nanocomposites has the highest tensile strength and flexural strength.B.OMMT composite was better than A.OMMT composites. But the impact strength decreased with the addition percent of MMT and the decreasing trend was rapidly. Two different kinds of MMT nano-composites had different flame-retardant effects.With the increasing amount of MMT, the increasing rate of limit Oxygen index of B.OMMT was faster than A.OMMT. Meanwhile,B.OMMT was good agent into carbon so that composites did not collapse after burning and having a whole burned shape better than A.OMMT.The XRD analysis showed that two kinds of nanoclays have formed intercalated structure.Interlayer spacing of B.OMMT was bigger than A.OMMT. The disappear of peak showed that detachment structure was formed.The SEM analysis showed that when 5 phr B.OMMT added,the composite phase interface between OMMT and HDPE is relatively vague.With increasing amount of OMMT, a large number of MMT reunited. DSC analysis revealed two kinds of MMT had reduced the crystallinity of the composite material and the effect of B.OMMT was relatively small.The larger the amount of addition, the worse the crystallinity was.And the amount of OMMT had less impact on melting point of composite material.TG analysis show that the addition of OMMT reinforced the heat resistance of the composite material.Heat resistance of B.OMMT composite was better than A.OMMT composite.Under certain addition amount, the more B.OMMT added,the better thermal stability was.Tested by TEM analysis revealed that dispersibility of B.OMMT was better than A.OMMT.The results of HDPE/POE/MMT research showed that:as to HDPE/POE system, with the increasing amount of POE added, the tensile strength and flexural strength reduced,the impact strength increased.Elongation at break increased with the increasing POE content.Taking all factors into consideration, the optimum additive amount of MMT was 10 phr.As to HDPE/POE/OMMT composite, with increasing amount of MMT, the tensile strength of the system gradually increased and the impact strength increases firstly and then decreased.At last,the best mass fraction of MMT was 5 phr.The DSC result showed that the mass fraction of the OMMT had less effect on melting point of the system.The TGA tests showed that MMT can improve the thermal stability of the composite material. The SEM analysis showed that when amount of OMMT was 5 phr,OMMT had the good dispersion in the system. The TEM analysis showed that OMMT had better dispersed in the system and intercalated structure was formed.As to HDPE/POE-g-MAH composite,the parameter of extrusion such like shear temperature and revolution speed played a very important role on the mechanical property of composites.When the shear temperature rose or the revolution speed accelerated,the overall mechanical properties got decreased.So,The best temperature and speed was 185℃ and 80 r/min.With 5 percent of MMT added,the composite had the best mechanical properties.When POE-g-MAH was added 10 percent,the composites held the best overall performance.According to TGA tests showed that the thermal decomposition temperature and heat resistance of the system had been improved because of MMT added.The DSC analysis tests showed MMT reduced the crystallization properties of the system and had no effect on the melting point of the system. Tested by SEM analysis showed that phase interface between the two phases became fuzzy after POE-g-MAH added to the system.Compatibility became better at the same time. Testing by TEM analysis showed that, POE-g-MAH was added to the system, the MMT evenly distributed in the system.The layer spacing increased and sheet was distorted. At last,the TEM picture showed detachment structure appeared.