Research On Rheological Properties Of Polyethylene/Montmorillonite Nanocomposite

Polyethylene(PE)/montmorillonite(MMT)nanocomposites with different MMT contentwereprepared by in situ polymerization of ethylene with organic montmorillonite (OMMT)and MgCl2supported Ziegler Natta catalyst. The preparation condition and the effect ofMMT content on thermal property and rheological behavior of PE/MMT nanocompositewere researched, which provides important basis data for the molding process ofnanocomposite.The effect of the preparation conditions of catalystwhich are alcohol content,Al/Timolar ration and the temperature of polymerizationon bulk density of PE/MMTnanocomposite have been researched. The results show that: the bulk density of compositeincreases with the increases of alcohol content, Al/Timolar ration and the temperature ofpolymerization, when the n alcohol: n MgCl2molar ration is4:1, the Al/Timolar ration is5:1and the temperature of the polymerization is80℃, the bulk density of composites reachesthe highest.The thermal property and MMT content of PE/MMT nanocomposite were characterizedby TGA. The results show that: PE1has the highest thermal decomposition temperature,theinitial decomposition temperature and the termination decomposition temperature are451.9℃a nd488.3℃respectively, which shows the excellent thermal stability of composite;at the same time the MMT content of composites is studied accurately.The melting behavior and crystallization behavior of PE/MMT nanocomposite werecharacterized by DSC. The results show that the highest melting and crystallizationtemperature of the composite are133.1℃a nd118.6℃respectively, the highestcrystallinitydegreeof the composite is71.5%.The effect of MMT content on the rheological behavior of PE/MMT nanocomposite hasbeen characterizedby means of Haake rheometer. The results show that the melt flow rule ofPE/MMT nanocomposite is basically the same with high density polyethylene (HDPE) andlow density polyethylene (LDPE). The viscosity of PE/MMT nanocomposite increasesand then decreases with the increases of MMT content, When the MMT content is4.58%,the viscosity obviously lower than HDPE and LDPE, which is useful for the molding processof the composite. PE/MMT nanocomposite is pesudoplastic fluid, the non newtonian index is in the range of0.5~0.6at190℃~230℃, which increases with the increases of temperature,and decreases and then increases with the increases of MMT content.The effect of MMT content on the dynamic rheological behavior of PE/MMTnanocomposite has been characterized by means of DHR IV dynamic rheometer. The resultsshow that with the increases of MMT content,the storage modulus, loss modulus, complexviscosity and flow activation energy of PE/MMT nanocomposite increase and then decrease,the tanδdecreases and then increases,and all above are lower than HDPE. When the MMTcontent is4.58%, the tanδimproves and the flow activation energy decreases22.4%bycompared with HDPE, which is useful for the molding process of the composite.The effect of MMT content on the melt flow index of PE/MMT nanocomposite hasbeen characterized by means of melt flow index indicator. The results show that: the meltflow index decreases and then increases with the increases of MMT content, and lower thanHDPE. When the MMT content is4.58%, the melt flow index improves489%by comparedwith HDPE, which is useful for the molding process of the composite.