The Design Of Fluid Viscosity Measuring Device At High Pressure And Experimental Study Of Polymer Melt Viscosity Pressure Sensitivity

The viscosity parameter is the most important parameter for the development of the material formulation and processing conditions to get the optimal intrinsic quality and appearance.Along with the development of polymer processing to high precision and high performance,viscosity parameter got more and more attention.Previous research on the influence factors of polymer viscosity focus on the temperature and pressure,ignoring the effect of pressure on viscosity.In this paper,a high pressure fluid viscosity test device was designed to test the viscosity of linear low density polyethylene(LDPE),polypropylene(PP)and polystyrene(PS)under different pressure.The influence mechanism of molecular structure,shear rate and temperature on viscosity sensitivity was analyzed.Using the method of constant shear rate,constant shear stress method and the superposition method calculate the viscosity pressure sensitivity coefficient of LDPE,PP and PS,comparing the difference and relation of the three methods.The PP\Nano-CaC03 composites materials were prepared by a self-designed stretching mixer,and the viscosity pressure sensitivity coefficient of the composites was calculated by the constant shear rate method and the constant shear stress method.High pressure fluid viscosity test device has multiple order partial pressure type mouth mold components.It can increase pressure and part pressure effectively.In the test,got three different pressure sensitivity coefficients at one time,the polymer melts pressure dependence of viscosity can be observed directly and it improve the efficiency of experiment.Using the method of constant shear rate,constant shear stress method and superposition calculate the viscosity pressure sensitivity coefficient of LDPE,PP,PS.The pressure sensitive relationship of three kinds of material as followed:PS>PP>LDPE.It was found that the stronger the molecular rigidity,higher viscosity pressure sensitivity coefficient.As the shear rate and temperature increase,the viscosity pressure sensitivity coefficient decreases.The viscosity pressure sensitivity coefficient(??)calculated with constant shear rate decrease with the increase of shear rate.The viscosity pressure sensitivity coefficient(??)calculated with constant shear stress is a constant value.The viscosity pressure sensitivity coefficient(??)has relationship with ??,and ??.?? more close to ?? and ???n?.The PP\Nano-CaC03 composites were mixed with different tensile clearances.The experimental results show that the Nano-CaC03 particles dispersed in the PP is best when the h=1000?m.The pressure sensitivity coefficient of PP\Nano-CaC03 composites is calculated.The experimental results show that the viscosity pressure sensitivity decreases with the increase of Nano-CaC03 mass fraction.When the mass fraction of Nano-CaC03 is lower(5%),the viscosity pressure sensitivity coefficient of the composites is slightly higher than that of pure PP and the pressure sensitivity coefficient is lower than that of pure PP,when the mass fraction of Nano-CaCO3 is high(10%,15%).