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Effect of the Vibration Force Field on Rheological Behavior and Compatibility of PP/PS/SBS Blends

Author: ZhouLei
Tutor: LiuYueJun
School: Hunan University
Course: Materials Processing Engineering
Keywords: vibration force field blend compatibility rheological behavior compatibilizer
CLC: TB332
Type: Master's thesis
Year: 2010
Downloads: 35
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Abstract

Melt flow state has profoundly changed since the vibration force field was introduced into the melt extrusion process. Therefore, it’s difficult to describe the complex rheological behavior accurately by using mathematical models at present. For blends, the compatibility is the key factor to determine the rheological behavior. However, for conventional methods to measure the compatibility of polymer blends, it’s difficult to characterize the compatibility of many components and analyze the internal relations between the vibration force field and the compatibility of blends melt.In this paper, the approximations of shear stress, shear rate and apparent viscosity are obtained to characterize the viscous behavior under vibration force field by the approximate treatment of the capillary velocity distribution v z and the capillary instantaneous volume flow rate Q (t )of the polymer melts which flows through the capillary. And the approximation of die swell ratio is measured to characterize the elastic behavior under vibration force field. At the same time, a parameter△I which reflects the size of the relative viscosity of blends has been summarized to characterize the compatibility of blends based on the experimental data of several groups of different compatibility blends. When parameter△I≥0, blends are compatible, while incompatible when△I<0. So the amount of parameter△I may reflect the interactions among the molecules of the blends, and among the blends, as well as the internal friction of blends. Namely, it may macroscopically reflect whether the compatibility of blends is good or bad.The rheological behavior and compatibility of the different weight ratio of PP/PS/SBS blends under the vibration force field are studied by using the parameter△I of the size of the relative viscosity of blends and using the multi-functional and all-electric polymer rheology test device. The result shows as follows:1.Whether under the effect of vibration force field or steady-state extrusion, as the blend mass ratio changes, there is minimum or maximum value of the apparent viscosity in a blend ratio. After introducing vibration force field, the apparent viscosity and the melt die swell ratio of blend melt are decreased obviously, and the melt also show non-Newtonian fluid and meet the power-law equation compared with the steady-state extrusion. While the amplitude and other conditions remain unchanged, the apparent viscosity and die swell ratio of the blends is in fluctuation state with the increase of the frequency; when the frequency and other conditions are of the same circumstances, the apparent viscosity and die swell ratio of the blends decreases gradually with the increase of the amplitude.2 . As the melt temperature increases, the parameter△I of PP/PS/SBS blend changes from negative to positive, while the△I of PP/PS blend does not change significantly, showing fluctuations state. And when the other conditions remain unchanged, with the SBS content increasing, parameter△I changes from negative to positive basically; while parameter△I changes from negative to positive under the vibration force field, and there is a maximum when the blend ratio is PP/PS/SBS = 60/30/10. It’s also found that when the blend ratio is PP/PS/SBS=60/32.5/7.5 and amplitude is 0.3mm, the compatibility of the blends is the selective enhancement with the increase of the frequency; when the blend ratio is PP/PS/SBS=60/32.5/7.5 and frequency is 20Hz, the compatibility of the blend increases gradually with the increase of the amplitude. Furthermore, after having the SEM scanning and mechanical property test on steady extruded sample and dynamic extruded sample, we find that the introduction of vibration force field can promote the dispersion of the SBS and the compatibility of the blends, and can reduce the amount of compatibilizer by up to 7.5%.This research provides an important experimental basis and theoretical guidance to optimize formulations of polymer blends and choice processing technology under the vibration force field.

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