The Rheology And Morphology Of Metallocene Polyethylene/Conventional Polyethylene Blends

The rheology properties and morphology of the different proportion blends of metallocene polyethylene(mPE) and conventional polyethylene(LDPE, LLDPE) has been studied in detail including the relationships of shear stress and temperature to apparent viscosity and shear rate. All the melts are pseudoplastic fluid and shear-thinning properties increase as the content of the conventional polyethylene increase in the blends. Melt flow-activation energy decrease regularly with the increase of mPE composition.The mechanical properties of different proportion blends for metallocene polyethylene and conventional LDPE has been studied by Stretcher. The result are shown that the tensile strength, yielding strength and breaking elongation increase when adding mPE in LDPE and LLDPE.In mPE/LDPE and mPE/LLDPE melts, apparent viscosity and Non-Newtonian exponent decrease when LDPE and LLDPE added in. Blends rheology change remarkably by contrast with mPE melt. Shear-thinning properties and flow-activation energy increase as adding LDPE and LLDPE in. Melt pseudoplasticity increases and rheology to temperature become sensitive. In a certain range of temperature and shear rate apparent viscosity fall, and fluidity and processibility are improved.In metallocene polyethylene/linear low density polyethylene/low density polyethylene melts(mPE/LLDPE/LDPE), The results are shown that melt flow-activation energy and expansion ratio varies regularly to the increasing of mPE. All the melts are pseudoplastic fluid and shear-thinning properties increase as the content of LLDPE increase in blends.In mPE/ LDPE blends, the crystallization, crystalform has been studied by using DSC, PM, SALS including the influence of contents and temperature to crystallization. The crystallization rate and crystallinity decrease when adding in LDPE. Within a blend composition proportion, phase separation is found in these blends during low dropping temperature rate and heating rate, but it doesn't happen at high dropping temperature and heating rate, and this is favourable for keeping mPE's characteristic of intensity and uniformity.PM and SALS results are shown the photos of black crux extinction, and black crux extinction become more clearer as mPE contents increase gradually. There are spherocrystal in all the blends and it is bigger and more complete when mPE is more, because mPE molecules are high isotacticity of chain structure and they are apt to be crystallized. SEM show the micrographs of mPE/LDPE blends that is compatible system and mPE molecules distribute uniformly in large scale.