| Ethylene/?-olefin copolymer with high comonomer incorporation is a new type of thermoplastic elastomer,which has the properties of both rubber and thermoplastic plastics and has a wide range of applications.However,the production of polyolefin elastomers is limited to laboratory studies in China.In order to develop a process package for POE production,complete the design of continuous solution polymerization process,processing technologies,the rheological properties of semi-dilute POE solution and melt were investigated,and the models for calculating these apparent viscosity were established.The relationships among the viscosity of the semi-dilute solution and melt of POE,the structure parameters,such as molecular weight,concentration,comonomer insertion,temperature,the shear rate and the type of solvent were experimentally studied.The main results of this paper include:(1)The rheological properties of semi-dilute solution of POE were studied experimentally under the temperature range of 90?140 ?,the concentration range of 8?30wt%,the shear rate range of 0.01?600s-1,the weight-average molecular weight range of 4.2×104?1.24×105g·mol-1,and n-hexane and Isopar-1 were used as solvent.The results show that the semi-dilute solution of POE in above range is pseudoplastic fluid.The viscosity of the solution continuously decreases with increasing temperature,and increases exponentially with increasing molecular weight and concentration of POE.The different co-monomer contentin does not significantly affect the viscosity of semi-dilute POE solution.Under the same conditions,the viscosity of POE/n-hexane solution is lower than that of the POE/Isopar-E solution.(2)The rheological curve of semi-dilute POE solution are related by the three-parameter Sisko equation,and the fitting correlation coefficient is about 0.99.When using the same solvent,the non-newtonian index of the semi-dilute solution of POE is close,and the POE/Isopar-E system is about 0.02,the POE/n-hexane system is about 0.05.The viscous flow activation energy corresponding to the infinite shear viscosity of semi-dilute solution mainly depends on the type of solvent.The activation energy of viscous flow in POE/n-hexane solution is about E1 J·mol-1 and the POE/Isopar-E solution is about E2 J·mol-1.(3)Based on the Sisko equation,the Arrhenius equation,and the direct correlation between the viscosity and the product of molecular weight and concentration derived in this paper,a prediction model among the apparent viscosity of semi-dilute solution of POE and molecular weight,concentration,temperature,the shear rate,was established,The average relative error of the POE/Isopar-E system is 20.5%,and the average relative error of the POE/hexane system is 23%.It has high precision for high-viscosity systems,especially in the medium to high shear rate range.(4)The chain structure of several polyolefin elastomer(POE)samples was characterized by GPC and NMR.Their melt flow stability at high extrusion rate,melt viscosities at various shear rates and temperatures are investigated by capillary rheometer.The relationship between the chain structure and the melt viscosity are analyzed.It is indicated that with an increase in shear rate,the polymer melt with higher molecular weight will appear unstable flow and the surface of the melt extrudate was distorted.The critical shear rate becomes lower if the molecular weight and co-monomer content are higher,and the temperature is lower.The shear viscosity of POE is largely influenced by the molecular weight,and is almost irrelevant to the co-monomer content.The polymer melts with various molecular weights and compositions have approximately the same viscous flow activation energy(?2.8×104 J·mol-1).The apparent viscous flow activation energy,decreases with the increase of the shear rate,When shear rate is higher than the critical shear rate,the viscous flow activation energy decreases sharply and approaches zero.(5)The Vinogradov-Malkin universal viscosity equation does not apply to the correlation of POE melt master curves,The correlation effects of Carreau equation and Cross equation on master curves are compared,among which Cross equations have the best correlation effect.Based on the Carreau equation,the Fox-Flory equation,the Arrhenius equation and the Cross equation,a prediction model among melt viscosity of POE with molecular weight,shear rate,and temperature was established.When the shear rate is higher than the critical shear rate,the average relative error calculated by this formula is 10.7%,otherwise,it is 18.7%.The model is available to predict the melt viscosity of POE in the range of temperature of 130?190?,shear rate of 10?2000s-1,and weight-average molecular weigh of 4.2×104?1.24×105 g·mol-1. |
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