Temperature correction on shear heating for the viscosity of PP/supercritical CO2 mixture at high shear rates

摘要

The theological behavior of PP/supercritical CO2(SCCO2) mixture at high shear rates was investigated with temperature correction in this study. An injection machine had been modified to generate the uniform CO2-containing PP melt. By measuring the pressure profile and flow rate of a slit die in front of the barrel during the injection procedure, and also monitoring the shear-induced temperature variation of the system, the dependence of viscosity on both shear rate and temperature then had been determined. A theoretical model based on the Cross model combined with the Eyring equation was proposed to correlate the shear-thinning behavior Of PP/SCCO2 mixture at various temperatures. The result revealed that the viscosity of PP melt was strongly influenced and reduced by the CO2 addition. Under the same temperature, the viscosity was reduced more significantly at lower shear rates. However, as shear rates were raised, the viscosity reduction diminished and eventually reached a stable value at extremely high shear rates. Moreover, the viscosity reduction would be decreasing when the temperature was getting higher. For PP/CO2 system, the correlation of viscosity data with shear rate at different temperatures could be well represented by a master curve. [References: 28]