Study On The Rheological Action Of U-PVC Dry Blends

U-PVC(unplastic PVC)pipes and profiles are widely used in many fields for their perfect mechanical and corrosion resistant properties.However,the gelation mechanism and rheological action of U-PVC dry blends are poorly understood because of the complex composition.The torque rheological curve can be used to describe the gelation behavior of U-PVC dry blends,but its application of instructing production process is restricted by the little understanding of the relationship between the gelation degree and viscosity of the melt.In order to solving this problem, the rheological action of U-PVC dry blends in a torque rheometer is studied by a SEM and a single-screw-extrusion capillary rheometer in this paper.In this paper,the morphological characteristics of U-PVC dry blends melted and gelated in a torque rheometer is studied by a SEM,and the law and reason of the torque increasing and decreasing are analyzed also.It is found that the grains of U-PVC resin are continuously dispersed into primary particles and their aggregates after the loading peak of the torque curve and the change of the torque is a united effect of many factors.The relationship between the rheological behavior of U-PVC compounds in a torque rheometer and the processing temperature and shear stress is studied in this paper.The result is shown that the shear stress and temperature are helpful to improve the degree of gelation and flow of the melt. The difference between the fusion peak and equilibrium torque is firstly used to characterize the degree of gelation.The data of the torque rheometer and the single-screw-extrusion capillary rheometer are united in this paper and the viscosity of the U-PVC compounds after being mixed in a torque rheometer is analyzed.It is shown that when U-PVC dry blends are mixed in a torque rheometer,the viscosity of the melt is decreased with the rise of the temperature.The gelation time is longer,the viscosity of the melt is bigger.If the melt have a large fusion peak,it must have a big value of viscosity.The experimental law of the viscosity of U-PVC melt is obtained.